JP5055688B2 - Ferrite material and inductor element - Google Patents

Description

  The present invention relates to a ferrite material and an inductor element, and more particularly to a ferrite material and an inductor element having excellent temperature characteristics.

Conventionally, Ni—Zn—Cu ferrite materials have been used as magnetic core materials or as inductor element materials such as multilayer chip inductors because of their magnetic properties. Since these magnetic cores and inductor elements are used in various environments, it is desirable that the magnetic cores and inductor elements are made of a material having a small change in initial permeability μ _i with respect to a temperature change, that is, a material having excellent temperature characteristics.

Patent Document 1 discloses an invention in which the temperature characteristics of initial permeability of a nickel-zinc ferrite material are improved. The present _invention, Fe ₂ O 3 43 to 50 mol%, NiO10～35 mol%, ZnO10～35 mol%, the basic composition of the nickel is CuO3~15 mol% - relative to the zinc ferrite material, _{an In} 2 _{O 3} Is a method for producing a nickel-zinc ferrite material, wherein 0.01 to 0.2% by weight is added and firing is performed. According to this invention, by adding In ₂ O ₃ to the basic composition of the nickel-zinc based ferrite material, the temperature characteristics of the initial permeability can be improved without reducing the initial permeability. Further, by using it as an oxide magnetic material for inductors, it can be easily combined with a chip capacitor having good temperature characteristics.

Japanese Patent Laid-Open No. 04-338166

However, in the case of the nickel-zinc based ferrite material described in Patent Document 1, the basic composition of the nickel-zinc based ferrite material (Fe ₂ O ₃ 43-50 mol%, NiO 10-35 mol%, ZnO 10-35 mol%) , CuO ₃ to 15 mol%), the amount of In ₂ O ₃ added is as small as 0.01 to 0.2% by weight, so the charge balance is lost, the temperature range showing the effect of improving temperature characteristics is narrow, and the effect of improving temperature characteristics At best, the improvement of about 1.5 ppm was the limit.

On the other hand, the temperature characteristic of the initial permeability μ _i of the ferrite material depends on the temperature changes of the saturation magnetization M _s and the magnetic anisotropy constant κ, as expressed by the following equation (1). The saturation magnetization M _s and the magnetic anisotropy constant κ both decrease as the temperature rises, and the magnetic anisotropy constant κ has a temperature region in which the amount of decrease is larger than the amount of decrease of the saturation magnetization M _s . in such a temperature range, as is apparent from the following (1), initial permeability mu _i jumps up large, so-called Hopkinson effect is expressed, initial permeability mu _i is varied greatly by changes in temperature not Become stable. In the following formula, a and b are constants, λ is a magnetostriction constant, and σ is stress.
μ _i ∝M _s ² / (aκ + bσλ) (1)
However, in the invention described in Patent Document 1, although an improvement in temperature characteristics is observed in a narrow temperature region where the magnetic anisotropy constant κ changes gradually, the magnetic anisotropy constant κ is reduced by the saturation magnetization M _s . There is a problem that it cannot cope with a wide temperature range in which the initial permeability μ _i jumps up by the Hopkinson effect.
Therefore, when such a ferrite material is used for an antenna, for example, the LC resonance frequency fluctuates due to a temperature change, and transmission / reception as an antenna becomes impossible.

  The present invention has been made in order to solve the above-described problems. The magnetic anisotropy constant itself is reduced to suppress the influence of the magnetic anisotropy constant on the initial permeability, and the temperature characteristics of the initial permeability are greatly increased. It is an object to provide a ferrite material and an inductor element that can be improved.

Ferrite material according to claim 1 of the present invention, 43 to 50.5 mol% of _Fe 2 _O 3, 10 to 48 mol% of NiO, 0 to 34 mol% of ZnO, and 2-17 mol% of CuO The basic material is a ferrite material containing 0.1 to 7.0 mol% of In ₂ O ₃ alone in the ferrite material, and the relative temperature of initial permeability in a temperature range of −25 ° C. to 100 ° C. The coefficient is in a range of ± 1.00 ppm / ° C. or less.

  According to a second aspect of the present invention, there is provided an inductor element comprising the magnetic body made of the ferrite material according to the first aspect.

And Thus, a ferrite material of the present invention, 43 to 50.5 mol% of _Fe 2 _O 3, 10 to 48 mol% of NiO, basic 0-34 mol% of ZnO, and 0-17 mol% of CuO A Ni—Zn—Cu ferrite material having a composition, and having this basic composition, can be reliably sintered as a ferrite material.

Therefore, even if the content of Fe ₂ O ₃ is less than 43 mol% or more than 50.5 mol%, it is not preferable because a different phase is not precipitated and sintered at a predetermined firing temperature.

  Moreover, even if the content of NiO is less than 10% or more than 48 mol%, it is not preferable because a heterogeneous phase is not precipitated and sintered at a predetermined firing temperature.

  ZnO is a component that controls the initial permeability, and the initial permeability can be increased by relatively decreasing the NiO content in response to an increase in the ZnO content. Therefore, it is not necessary to add ZnO, but in this case, there is no effect of increasing the initial permeability and the initial permeability is reduced. If the ZnO content exceeds 34 mol%, it is not preferable because a heterogeneous phase is precipitated and sintered at a predetermined firing temperature.

  CuO is a component that improves the sinterability, and can lower the firing temperature to 1000 ° C. or lower. As a result, the internal electrode can be co-fired like a multilayer electronic component such as a multilayer inductor. When the content of CuO exceeds 17 mol%, it is not preferable because a heterogeneous phase is precipitated and does not sinter.

The ferrite material of the present invention contains 0.1 to 7.0 mol% In ₂ O ₃ . This content is 0.23 to 15.5% by weight in terms of weight. By containing 0.1 to 7.0 mol% of In ₂ O ₃ with respect to the ferrite material, a part of Fe ³⁺ ions of Fe ₂ O ₃ which is a basic component of the ferrite material is actively used with In ³⁺ ions. Can be substituted. By this substitution, the magnetic anisotropy constant κ of the ferrite material can be reduced, and the influence of the decrease in the magnetic anisotropy constant κ on the decrease in the saturation magnetization M _s due to the Hopkinson effect can be suppressed. Therefore, as is clear from the relationship of the above equation (1), the effect of temperature change on the initial permeability μ _i is suppressed, the temperature characteristics of the ferrite material are improved, and the stable initial permeability μ is obtained in a wide temperature range. _i can be obtained.

When the content of In ₂ O ₃ is less than 0.1 mol%, the Fe ³⁺ ions cannot be replaced with In ³⁺ ions, the addition effect is not observed, and the temperature characteristics of the initial permeability μ _i cannot be stabilized. Therefore, it is not preferable. On the other hand, if the content of In ₂ O ₃ exceeds 7.0 mol%, the Curie temperature _Tc is lowered and the magnetic permeability may not be obtained.

  The ferrite material of the present invention has, for example, a temperature range of −25 ° C. to 100 ° C. of initial permeability, a small relative temperature coefficient and a temperature change rate, and excellent temperature characteristics. It can be used as a low-loss material for millimeter wave or microwave isolators.

  The inductor element of the present invention is an inductor element having a magnetic body formed of the ferrite material of the present invention and having excellent temperature characteristics in a wide temperature range. Examples of the inductor element of the present invention include a laminated inductor and a wound inductor used in mobile equipment such as a mobile phone. For example, in the case of a multilayer inductor, when a magnetic body is formed from the ferrite material of the present invention, a conductive metal having a low melting point such as Ag, Cu and an alloy containing these as a main component is co-fired at 1000 ° C. or less. By this, an internal coil can be formed. When the inductor element of the present invention is used in combination with a capacitor, the resonance frequency is stabilized in a wide temperature range, and an LC resonance circuit having a stable resonance frequency can be configured.

According to the onset bright, it is possible to greatly improve the temperature characteristic of the initial permeability by suppressing the influence on the initial permeability of the magnetic anisotropy constant to reduce the magnetic anisotropy constant itself, moreover basic composition ferrite material and inductor elements Ru can be fired at 1000 ° C. or less of the temperature by containing CuO as can be provided.

  First, the ferrite material of the present invention will be specifically described.

(1) Preparation of Ferrite Material First, NiO, ZnO, CuO, Fe ₂ O ₃ and In ₂ O ₃ powders were prepared as starting materials. Thereafter, each powder of these starting materials was weighed and blended so as to have the contents shown in Sample Nos. 1 to 28 in Table 1, and then each blended product was partially stabilized zirconia balls as cobblestones. Wet mixing was performed for 24 hours using a pot mill. Then, after drying these blends, after calcining at a predetermined firing temperature (for example, 650-750 ° C.), the calcined powder is adjusted so that the specific surface area becomes about 5 m ² / g. Ferrite raw material powder was obtained by grinding for about 8 hours with a pot mill. In Table 1, samples marked with * are outside the scope of the present invention.

(2) Preparation of ferrite sintered body After each of the above ferrite raw material powders was mixed with a vinyl acetate binder solution to obtain a slurry, these slurries were dried. Next, using these dry powders, a dry press molding machine is used to produce block-shaped powder compacts, and these powder compacts are fired at a predetermined firing temperature (for example, 900 to 1000 ° C.) in the atmosphere. Was fired for about 1 to 2 hours to obtain a toroidal core-shaped ferrite sintered body. As impurities derived from starting materials, Mn, Cl, Ni, Zn, Mg, S, Ca, Cr, Bi, etc. are mixed in less than about 0.40% by weight, or impurities during mixing and grinding include Zn and Although Si may be mixed in less than 0.8% by weight, there is no particular problem in view of the ferrite material characteristically.

(3) Evaluation of ferrite sintered body Next, each of the above toroidal core-shaped ferrite sintered bodies was wound with an annealed copper wire for 40 turns, and each inductance was measured using an impedance analyzer at a frequency of 100 kHz. At this time, the toroidal core is installed in a thermostatic bath, and as shown in Table 1, the temperature of inductance is changed in the range of −25 to 100 ° C., and the temperature change of the inductance is measured. The relative temperature coefficient α _μr of the magnetic _{susceptibility} μ _i was calculated based on the following equation (2), each sample was evaluated, and the results are shown in Table 1. In the following formula, μ _{100 ° C.} , μ _{−25 ° C.} , and μ _{25 ° C.} indicate initial permeability at 100 ° C., −25 ° C., and 25 ° C., respectively.
α _μr (ppm / ° C.) = [(μ _{100 ° C.−} μ− _{25 ° C.} ) / (μ _{25 ° C.} ² × 125)] × 10 ⁶
... (2)

Further, the temperature change rate Δμ / μ of the initial permeability μ _i from 25 ° C. to 100 ° C. is calculated based on the following equation (3), each sample is evaluated, and each result is shown in Table 1. It was.
Δμ / μ (%) = [(μ _{100 ° C.−} μ _{25 ° C.} ) / Μ _{25 ° C.} ] × 100 (3)

According to the results shown in Table 1, in the case of sample Nos. 2 to 4, Nos. 7 to 8, Nos. 11 to 13, Nos. 15 to 18, and Nos. 22 to 27 within the scope of the present invention, Since both have the basic composition of the present invention and the content of In ₂ O ₃ is 0.1 to 7.0 mol%, a part of Fe ³⁺ ions of Fe ₂ O ₃ which is the basic composition is converted to In ^3+. The magnetic anisotropy constant κ of the toroidal core can be reduced by positive substitution with ions, and the relative temperature coefficient α _μr of the initial permeability μ _i in the temperature range of −25 ° C. to 100 ° C. is ± 1.00 ppm. It was small in the range of / ° C, and the temperature change rate of the initial permeability µ _i was 14% or less with reference to 25 ° C, indicating that the temperature stability was excellent.

On the other hand, in the case of sample Nos. 20 and 21 having an In ₂ O ₃ content of less than 0.1 mol%, the relative temperature coefficient α _μr of the initial permeability μ _i is 1.38 ppm / ° C., or 1.19 ppm / ° C is large, the initial permeability μ _i changes from 980 to 1250, or from 980 to 1190 in the range from −25 ° C. to 100 ° C., and the temperature change rate Δμ / μ is 19% or more, or 13%. From the above, it was found that the temperature stability was inferior. In addition, in the case of Sample No. 29 in which the content of In ₂ O ₃ exceeds 7.0 mol%, it was found that the Curie temperature T _c is lowered and the magnetic permeability μ cannot be obtained.

Further, in any case of sample No. 1 in which the content of Fe ₂ O ₃ which is the basic composition of the ferrite material is less than 43 mol% and sample No. 5 in which the content exceeds 50.5 mol%, a different phase is present. It was found that it was deposited and not sintered as a ferrite material.

  It was found that even in the case of Sample No. 9 in which the content of CuO, which is the basic composition, exceeds 17 mol%, a heterogeneous phase precipitates and does not sinter as a ferrite material.

  In any case of sample No. 10 in which the content of NiO which is the basic composition is less than 10 mol% and sample No. 14 in which the content exceeds 48 mol%, a heterogeneous phase is precipitated and does not sinter as a ferrite material. understood.

  It was found that even in the case of Sample No. 19 in which the content of ZnO as the basic composition exceeds 34 mol%, a heterogeneous phase is precipitated and does not sinter as a ferrite material.

Next, the multilayer inductor of this embodiment using the ferrite material of the present invention as a magnetic material will be described with reference to FIG.
For example, as shown in FIG. 1, the multilayer inductor 10 of this embodiment includes a magnetic body 11 made of the ferrite material of the present invention, a coil 12 formed in the magnetic body 11, and upper and lower electrode portions of the coil 12. The inductor element is provided with a pair of left and right external electrodes 13A and 13B connected to 12A and 12B and covering both end faces of the sintered body 11, and having excellent temperature characteristics. The coil 12 includes a coil conductor 121 formed in a plurality of upper and lower stages in the horizontal direction and a via-hole conductor 122 that electrically connects the upper and lower coil conductors 121, and is formed as a rectangular spiral extending in the vertical direction. ing.

  When manufacturing the multilayer inductor according to the present embodiment, for example, the following manufacturing method is used. First, a slurry containing the ferrite raw material of the present invention is formed into a sheet by a doctor blade method to produce a plurality of ceramic green sheets. Next, after forming a via hole at a predetermined position of an appropriate ceramic green sheet, a conductive paste containing a conductive metal powder such as Cu is printed on the upper surface of the ceramic green sheet by using a screen printing method or the like. The coil pattern was formed. The required number of ceramic green sheets on which a predetermined coil pattern is formed are stacked, and the ceramic green sheets on which the coil pattern is not formed are stacked on both upper and lower surfaces thereof. A block was formed. Thereby, the coil pattern of each layer is connected by the via hole to form a laminated coil. And this press-bonded block was cut into a predetermined size to obtain a laminate. Next, after degreasing the laminate, the degreased laminate was fired at 900 ° C. to obtain a ferrite sintered body (magnetic body). And after performing the end surface processing of this magnetic body, the electrically conductive paste was apply | coated to the both end surfaces, and it baked at 700 degreeC, and formed the external electrode, respectively. As a result, a multilayer inductor having a coil incorporated in the magnetic body was obtained.

The present invention is not construed as being limited to the above embodiments, short, 43 to 50.5 mol% of _Fe 2 _O 3, 10 to 48 mol% of NiO, 0 to 34 mol% of ZnO, and 2-17 mol% of CuO an ferrites material shall be the basic composition, the magnetic body ferrite material and ferrite material containing _in 2 _{O 3} of 0.1 to 7.0 mol% inductor Any element is included in the present invention.

  The present invention can be suitably used as, for example, an inductor element of a mobile device such as a mobile phone.

FIG. 3 is a perspective view showing a perspective view of an embodiment of an inductor element of the present invention.

Explanation of symbols

10 Multilayer inductor (inductor element)
11 Magnetic material

Claims (2)

43 to 50.5 mol% of _Fe 2 _O 3, _10~48 mol% of NiO, a ferrite material having a basic composition 0 to 34 mol% of ZnO, and 2-17 mol% of CuO, the ferrite The material contains 0.1 to 7.0 mol% of In ₂ O ₃ alone, and the relative temperature coefficient of the initial permeability in the temperature range of −25 ° C. to 100 ° C. is within ± 1.00 ppm / ° C. Ferrite material characterized by that. An inductor element comprising a magnetic body made of the ferrite material according to claim 1.

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