JP5811860B2 - Ferrite sintered body and electronic parts - Google Patents

Description

  The present invention relates to a ferrite sintered body suitable for manufacturing a ferrite core such as an automobile transponder, choke coil, and inductor, and a coil component in which a winding is wound around, for example, a ferrite core composed of the sintered body. And so on.

  Ferrite cores composed of ferrite sintered bodies are mainly used for parts such as coil parts, sensors, antennas, deflection yokes, etc., and these parts have been used for various electronic devices.

  However, in recent years, portable devices such as mobile phones and notebook personal computers have rapidly spread. For example, a device incorporating a coil component is required to have a characteristic that can withstand harsh use environments, particularly temperature changes. Specifically, the usable temperature range covers a wide range, and the change in the initial magnetic permeability in the temperature range is small, preferably not changed at all.

  In recent years, coil parts have also been used for automobile parts such as tire pressure sensors such as transponders and control circuits in engine rooms. Characteristics that can be withstood are required.

  In addition, a coil component whose initial permeability is in a specific range is selected according to the application. Therefore, the coil component is required to have the initial permeability within a specific range in addition to the small temperature change of the initial permeability.

By the way, in Patent Document 1, in a Ni—Cu—Zn-based ferrite sintered body, a ferrite that can improve the relative temperature coefficient of initial permeability by setting the ratio of Fe ₂ O ₃ and ZnO within a specific range is disclosed. Have been described.

JP 2006-206420 A

  The present invention has been made in view of such a situation. In a wide temperature range (for example, −40 to 125 ° C.), the change rate of the initial permeability μi is small, and the initial permeability μi is in a specific range (for example, 700). An object of the present invention is to provide a ferrite sintered body in about ~ 1000) and an electronic component having a ferrite core composed of the ferrite sintered body.

In order to achieve the above object, a ferrite sintered body according to the present invention has a spinel structure and has a main component containing iron oxide, zinc oxide, copper oxide, and nickel oxide. It is. The ferrite sintered body has an A phase and a B phase. The A phase is a region in which the content ratio (mol%) of iron oxide in terms of Fe ₂ O ₃ is larger than the content ratio (mol%) of zinc oxide in terms of ZnO, and the B phase is Fe _{2 of} iron oxide. The content ratio (mol%) in terms of O ₃ is a region below the zinc oxide content ratio (mol%) in terms of ZnO. The content ratio of iron oxide in 100 mol% of the main component in terms of Fe ₂ O ₃ is x (mol%), and the area ratio of the A phase to the total area of the area of the A phase and the area of the B phase is y (% ), The variable (x, y) is in an area (including a line) surrounded by a rectangle whose vertices are the following points A to D.
Point A (48, 85)
Point B (48, 70)
Point C (49.9, 68)
Point D (49.9, 78)

In the ferrite sintered body according to the present invention, the content (mol%) of iron oxide in the main component in terms of Fe ₂ O ₃ and the area ratio (%) of the A phase are within a specific range. is there. By doing in this way, the rate of change of the initial permeability in a wide temperature range can be reduced, and the initial permeability can be set within a specific range.

  The electronic component which concerns on this invention is an electronic component which has a ferrite core comprised from the ferrite sintered compact as described above.

  Since the electronic component according to the present invention has a small temperature change of μi and μi is in a specific range (for example, about 700 to 1000), the coil component, the transformer component, the applied product in the frequency band from 1 Hz to 3 MHz, Suitable for magnetic head components. Examples of the coil component include a transponder for an automobile, an inductor, a choke coil, and the like. Examples of the transformer component include a power transformer for switching and an inverter.

FIG. 1 shows a ferrite core for a coil component according to an embodiment of the present invention. 2, the area of the content calculated as Fe ₂ O ₃ of iron oxide with respect to 100 moles of the main% of the ferrite sintered body as the x-axis, the A-phase to the total 100% of the area of the A-phase area and the B-phase It is a graph which made the ratio the y-axis. FIG. 3 is a graph in which the examples of the present invention and comparative examples shown in Table 2 are plotted on the graph shown in FIG.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

  As a ferrite core for coil parts according to the present embodiment, in addition to the drum type shown in FIG. 1, FT type, ET type, EI type, UU type, EE type, EER type, UI type, toroidal type, pot type, A cup type etc. can be illustrated. In FIG. 1, the coil component 10 is obtained by winding the winding 14 around the ferrite core 12 by a predetermined number of turns.

  The ferrite core 12 of the coil component 10 is composed of a ferrite sintered body according to this embodiment. The ferrite sintered body is Ni—Cu—Zn based ferrite, and its main component is composed of iron oxide, copper oxide, zinc oxide and nickel oxide.

  The ferrite sintered body according to the present embodiment is mainly composed of an A phase and a B phase. The sintered ferrite body may have a phase other than the A phase and the B phase.

In this embodiment, both the A phase and the B phase have at least iron oxide, copper oxide, zinc oxide, and nickel oxide as constituent components, and the A phase and B depend on the content ratio of iron oxide and zinc oxide. It is divided into phases. That is, the A phase is a region (phase) in which the content (mol%) of iron oxide in terms of Fe ₂ O ₃ is larger than the content (mol%) of zinc oxide in terms of ZnO. The B phase is a region (phase) in which the content (mol%) of iron oxide in terms of Fe ₂ O ₃ is equal to or less than the content (mol%) of zinc oxide in terms of ZnO.

In the present embodiment, the content of iron oxide in 100 mol% of the main component and the area ratio of the A phase with respect to 100% of the total area of the A phase and the B phase in the ferrite sintered body are controlled. . Specifically, when the content of Fe ₂ O ₃ in 100 mol% of the main component is “x” (mol%) and the area ratio of the A phase is “y” (%), the variable (x, y ) Are surrounded by a quadrangle having points A (48, 85), B (48, 70), C (49.9, 68) and D (49.9, 78) as vertices shown in FIG. It is within the area (including the line) (shaded area in FIG. 2). That is, in the main component 100 mol%, the content of iron oxide, calculated as _Fe 2 _{O 3} is from 48.0 to 49.9 mol%. The content of iron oxide is the amount that iron oxide occupies in terms of Fe ₂ O ₃ when the main component is 100 mol%, and is not the content in a specific phase.

In the ferrite sintered body, the content of the iron oxide in the main component and the area ratio of the A phase satisfy the above relationship, so that the initial permeability is in a specific range, and the ferrite sintered body The temperature characteristics of the initial permeability can be improved. Specifically, in each temperature range of −40 to 85 ° C., 25 to 85 ° C., and 25 to 125 ° C., the change rate (Δμi / μi _{25 ° C.} ) with respect to the initial permeability at 25 ° C. is −5.0 to +5. 0.0%.

  The method for obtaining the areas of the A phase and the B phase is not particularly limited, but in the present embodiment, for example, it can be obtained as follows. First, the ferrite sintered body is cut and polished. A surface analysis is performed on the polished surface of a specific region (for example, a 100 μm × 100 μm square region) using an electron beam microanalyzer (EPMA).

From the content ratio of each element obtained at the measurement point, a set (area) of measurement points in which the content ratio of Fe element in terms of Fe ₂ O ₃ is larger than the content ratio of Zn element in terms of ZnO is defined as A phase, and Fe A set (region) of measurement points in which the content ratio of the element in terms of Fe ₂ O ₃ is equal to or less than the content ratio of the Zn element in terms of ZnO is defined as a B phase.

  Then, the area of the A phase and the B phase is calculated by performing image processing or the like on the mapping image of the area subjected to the surface analysis, and the area ratio of the A phase may be calculated from these values.

  In addition, the whole area | region which performs surface analysis using EPMA does not need to be comprised from A phase and B phase, and phases other than A phase and B phase may exist in this area | region. Even in this case, the area ratio of the A phase is calculated as a ratio with respect to a total of 100% of the area of the A phase and the area of the B phase.

  The area ratio of the A phase and the B phase described above can be easily realized by controlling firing conditions and using a plurality of zinc oxide raw materials.

  The content of other components in the ferrite sintered body is not particularly limited as long as the content of iron oxide is in the above range, but in the present embodiment, it is preferably in the following range.

  In 100 mol% of the main component, the content of copper oxide is preferably 2.0 to 8.0 mol%, more preferably 4.0 to 6.0 mol% in terms of CuO.

  In 100 mol% of the main component, the content of zinc oxide is preferably 28.0 to 34.0 mol%, more preferably 30.0 to 32.0 mol% in terms of ZnO.

  In 100 mol% of the main component, the content of nickel oxide is preferably 12.0 to 20.0 mol%, more preferably 14.0 to 16.0 mol% in terms of NiO.

  In addition to the above main components, the ferrite sintered body according to the present embodiment may contain subcomponents in order to obtain desired characteristics as long as the effects of the ferrite sintered body are not reduced. . The subcomponent is not particularly limited, and examples thereof include tungsten oxide, molybdenum oxide, bismuth oxide and the like.

  In addition, the ferrite sintered body according to the present embodiment may include oxides of inevitable impurity elements.

  Specifically, B, C, Si, P, S, Cl, As, Se, Br, Te, I, Li, Na, Mg, Al, K, Ca, Ga, Ge, Sr, Cd, In, Typical metal elements such as Sn, Sb, Ba, and Pb, and transition metal elements such as Sc, Ti, V, Cr, Mn, Co, Y, Zr, Nb, Pd, Ag, Hf, and Ta can be given.

  Next, an example of a method for manufacturing a ferrite sintered body according to the present embodiment will be described.

First, a main component material is prepared as a starting material. As a raw material of the main component, iron oxide (α-Fe ₂ O ₃ ), copper oxide (CuO), zinc oxide (ZnO), nickel oxide (NiO), composite oxide, or the like can be used. In addition, various compounds that become oxides or composite oxides by firing can be used. Examples of the oxide that becomes the above-mentioned oxide upon firing include simple metals, carbonates, oxalates, nitrates, hydroxides, halides, organometallic compounds, and the like.

  As the raw material for zinc oxide, it is preferable to use two or more kinds of raw materials, and in particular, other raw materials (such as iron oxide) of the main component, a raw material to be calcined, and a raw material not to be calcined Is preferred.

  As a raw material not to be calcined, it is preferable to use metal zinc, zinc oxide, zinc carbonate, zinc chloride, a composite oxide containing zinc, or the like. By using two or more kinds of raw materials as the raw material for zinc oxide, it becomes easy to control the area ratio of the A phase described above in the sintered ferrite body after firing.

  When the ferrite sintered body contains a subcomponent, the component oxide, mixture, or composite oxide can be used as a subcomponent material in the same manner as described above. In addition, various compounds that become oxides or composite oxides by firing can be used.

  The prepared starting materials are weighed and mixed so as to have a predetermined composition ratio to obtain a raw material mixture. Examples of the mixing method include wet mixing using a ball mill and dry mixing using a dry mixer. In addition, it is preferable not to include the raw material which does not perform calcination in a raw material mixture, but to add after the calcination of the raw material mixture mentioned later. Further, it is preferable to use a starting material having an average particle diameter of 0.1 to 3 μm.

  Next, the raw material mixture is calcined to obtain a calcined material. The calcining is preferably performed at a temperature of 800 to 1100 ° C., usually for about 1 to 3 hours. The calcination may be performed in the air (air), or may be performed in an atmosphere having a higher oxygen partial pressure or in a pure oxygen atmosphere than in the air.

  Next, the calcined material is pulverized to obtain a pulverized material. The pulverization may be performed after coarse pulverization and further fine pulverization. The fine pulverization is preferably performed by wet pulverization using a ball mill or an attritor. The wet pulverization is performed until the average particle diameter of the calcined material is preferably about 1 to 2 μm. The raw material that is not calcined may be added before coarse pulverization of the calcined material, or may be added after coarse pulverization.

  Next, the pulverized material is granulated (granular) to obtain a granulated product. Examples of the granulation method include a pressure granulation method and a spray drying method. The spray drying method is a method in which a commonly used binder such as polyvinyl alcohol is added to the pulverized material, and then atomized in a spray dryer and dried at a low temperature.

  Next, the granulated product is molded into a predetermined shape to obtain a molded body. Examples of the molding of the granulated product include dry molding, wet molding, and extrusion molding. The dry molding method is a molding method in which a granulated product is filled in a mold and compressed and pressed (pressed). The shape of the molded body is not particularly limited, and may be appropriately determined according to the application. In the present embodiment, the shape is a toroidal shape.

  Next, the compact is fired to obtain a sintered body (ferrite sintered body of the present embodiment). The main baking is preferably performed at a temperature of 900 to 1300 ° C., usually for about 2 to 5 hours. The main calcination may be performed in the atmosphere (air) or in an atmosphere having a higher oxygen partial pressure than in the atmosphere.

  The ferrite sintered body according to the present embodiment is manufactured through such steps.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, Of course, in the range which does not deviate from the summary of this invention, it can implement in various aspects. .

  For example, in the above-described embodiment, in order to obtain a toroidal shape, the shape is formed before the main baking, but may be formed (processed) after the main baking.

  Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.

First, as raw materials for the ferrite sintered body, Fe ₂ O ₃ , NiO, CuO, ZnO and raw materials shown in Table 1 were prepared.

Next, each powder of Fe ₂ O ₃ , NiO, CuO, and ZnO was weighed and then wet-mixed with a ball mill for 5 hours to obtain a raw material mixture.

Next, the obtained raw material mixture was calcined in the air at 900 ° C. for 2 hours to obtain a calcined material. To this calcined material, the raw materials shown in Table 1 are added to 100% by weight of the calcined material within the range shown in Table 1, and wet pulverized with a ball mill until the specific surface area becomes 3 m ² / g. Obtained material. ZnO shown in Table 1 is a powder obtained by mixing a powder having an average particle diameter of 5 μm and a powder having an average particle diameter of 1 μm at a ratio of 1: 1.

  Next, after drying this pulverized material, 10% by weight of polyvinyl alcohol (3% by weight aqueous solution) as a binder was added to 100% by weight of the pulverized material, granulated, and sized with a 20 mesh sieve. Granules were used. This granule was press-molded at a pressure of 100 kPa to obtain a toroidal shaped compact.

  Next, each of these molded bodies was fired in air at 1150 ° C. for 2 hours to obtain a toroidal core sample (outer diameter 18 mm × inner diameter 10 mm × height 5 mm) as a sintered body. The obtained sample was subjected to fluorescent X-ray analysis to measure the composition of the ferrite core. Moreover, the following characteristic evaluation was performed with respect to the ferrite core.

(Measurement of area ratio of A phase and B phase)
The obtained sample was cut, embedded in resin, polished, and EPMA analysis was performed on the polished surface. Using an electron beam microanalyzer (EPMA-1600 manufactured by Shimadzu Corporation), mapping analysis was performed on a 100 μm × 100 μm square region under conditions of an acceleration voltage of 15 kV, an irradiation current of 0.3 μA, and a counting time of 60 seconds.

  From the magnitude of the content ratio of Fe element and Zn element at each measurement point in the obtained mapping analysis, the area ratio was obtained by dividing into the A phase and the B phase in the measurement region. The results are shown in Table 2 and FIG.

(Initial permeability (μi))
After winding the winding around the obtained toroidal core sample 20 times, the initial permeability μi was measured using an LCR meter (4284A manufactured by Agilent). The measurement conditions were a measurement frequency of 1 kHz, a measurement temperature of 25 ° C., and a measurement level of 0.4 mA. In this example, a sample having an initial permeability in the range of 700 to 1000 at 25 ° C. was considered good.

(Temperature characteristics of initial permeability)
Subsequently, the initial permeability (μi) at −40 to 125 ° C. was measured under the above measurement conditions. From the obtained initial permeability, the rate of change (Δμi / μi) relative to the initial permeability at 25 ° C. was calculated. In this example, Δμi / μi (−25 ° C.) at _{−40 to} 25 ° C. (= μi− _{40 ° C.} −μi _{25 °} C./μi _{25 ° C.} ) is good from −5 to + 5%, and Δμi / at 25 to 85 ° C. μi (85 ° C.) (= μi _{85 ° C.} −μi _{25 °} C./μi _{25 ° C.} ) is preferably −5 to + 5%, and Δμi / μi (125 ° C.) at _{25 to 125 ° C.} (= μi _{125 ° C.} −μi _{25 ° C.} / Μi _{25 ° C.} ) made -5 to + 5% good. The results are shown in Table 2.

From Table 2, when x (Fe ₂ O ₃ content) and y (A phase area ratio) are within the above-described ranges (Examples 1 to 18), the initial magnetic permeability in a wide temperature range. Further, it was confirmed that the temperature change of the initial magnetic permeability was in a specific range (700 to 1000). From FIG. 3, it was visually confirmed that Examples 1 to 18 were in an area surrounded by a quadrangle having points A to D as vertices.

Claims (2)

A ferrite sintered body having a spinel structure and having a main component including iron oxide, zinc oxide, copper oxide, and nickel oxide,
The ferrite sintered body has an A phase and a B phase,
The A phase is a region in which the content ratio (mol%) of the iron oxide in terms of Fe ₂ O ₃ is larger than the content ratio (mol%) of the zinc oxide in terms of ZnO, and the B phase is The content ratio (mol%) of iron oxide in terms of Fe ₂ O ₃ is a region below the content ratio (mol%) of zinc oxide in terms of ZnO,
The content ratio of the iron oxide in 100 mol% of the main component in terms of Fe ₂ O ₃ is x (mol%), and the area of the A phase with respect to the total area of the area of the A phase and the area of the B phase proportion when the y (%), the variable (x, y) is, in the area surrounded by the quadrangle with apexes A~D following points (including the line) near is,
The initial permeability at _{25 ° C.} is μi _{25 ° C.}
When the initial permeability at _{125 ° C} is μi _{125 ° C} ,
_{(Μi 125 ℃ -μi 25 ℃)} / ferrite sintered body .mu.i _{25 ° C.} is characterized -5 + 5% der Rukoto.
Point A (48, 85)
Point B (48, 70)
Point C (49.9, 68)
Point D (49.9, 78)   The electronic component which has a ferrite core comprised from the ferrite sintered compact of Claim 1.

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