阅读说明：本技术 Ni－Zn－Cu系铁氧体粉末、烧结体、铁氧体片 (Ni-Zn-Cu ferrite powder, sintered body, and ferrite sheet ) 是由 野村吏志 西尾靖士 中务爱仁 冈野洋司 藤井泰彦 于 2019-03-12 设计创作，主要内容包括：本发明的目的在于提供一种即使在例如860℃的低温下也能够烧结的Ni－Zn－Cu系铁氧体粉末。本发明涉及的Ni－Zn－Cu系铁氧体粉末的特征在于：含有49mol％以下的Fe<Sub>2</Sub>O<Sub>3</Sub>、5～25mol％的NiO、15～40mol％的ZnO、5～15mol％的CuO和0～3mol％的CoO,微晶尺寸为180nm以下,并涉及使用了该Ni－Zn－Cu系铁氧体粉末的烧结体或铁氧体片。(The purpose of the present invention is to provide a Ni-Zn-Cu ferrite powder that can be sintered even at a low temperature of, for example, 860 ℃. The Ni-Zn-Cu ferrite powder according to the present invention is characterized in that: containing 49 mol% or less of Fe 2 O 3 5 to 25 mol% NiO, 15 to 40 mol% ZnO, 5 to 15 mol% CuO and 0 to 3 mol% CoO, and a sintered body having a crystallite size of 180nm or less, and a sintered body using the Ni-Zn-Cu ferrite powderOr ferrite pieces.)

1. A Ni-Zn-Cu ferrite powder characterized by comprising:

containing 49 mol% or less of Fe₂O₃5-25 mol% of NiO, 15-40 mol% of ZnO, 5-15 mol% of CuO and 0-3 mol% of CoO, wherein the crystallite size is less than 180 nm.

2. The Ni-Zn-Cu-based ferrite powder according to claim 1, wherein:

the strain is 0.330 or less.

3. The Ni-Zn-Cu-based ferrite powder according to claim 1 or 2, characterized in that: the sintered density was 5.00g/cm after firing at 860 ℃ in the air³The above.

4. A sintered body, characterized in that:

the Ni-Zn-Cu ferrite powder according to any one of claims 1to 3 is used.

5. A ferrite sheet, comprising:

the Ni-Zn-Cu ferrite powder according to any one of claims 1to 3 is used.

Technical Field

The present invention relates to a Ni — Zn — Cu-based ferrite material, a ferrite powder which can be sintered at a low temperature, and a sintered body and a ferrite sheet using the ferrite powder.

Background

In recent years, electronic devices for home use, industrial use, and the like have been reduced in size and weight, and accordingly, there has been an increasing demand for electronic components used in the above-mentioned various electronic devices to be reduced in size, increased in efficiency, and increased in frequency.

For example, a ferrite sintered type laminated chip inductor has been put to practical use from a wound type in which a coil is formed by winding a copper wire having an insulating coating on a core or an air-core bobbin, which is used for an electronic circuit of an electronic device.

The multilayer chip inductor is manufactured through the following manufacturing steps. That is, a paste containing ferrite powder is formed into a sheet to form a green sheet, and a paste containing an electrode material such as Ag or Ag — Pd is used to form a conductive pattern on the green sheet by printing or the like, and then the conductive pattern is stacked and sintered at a predetermined temperature to form an external electrode.

However, as described above, in the manufacturing process of the multilayer chip inductor, a method of firing the laminate of the electrode material and the ferrite at the same time is adopted, and therefore, there is a problem that the original properties of the ferrite are deteriorated due to the interfacial reaction (interdiffusion) between the electrode material such as Ag or Ag — Pd and the ferrite, and in order to avoid this problem, firing at a low temperature of about 900 ℃.

However, when firing is performed at a temperature of 900 ℃ or lower, it is difficult to obtain a sintered Ni-based ferrite excellent in electromagnetic properties such as magnetic permeability as a magnetic material for a multilayer chip inductor.

Several techniques have been proposed for the Ni — Zn — Cu-based ferrite powder, which can be sintered at a low temperature. For example, there is a method of adding borosilicate glass as a sintering aid to generate a liquid phase during sintering and promote the growth of ferrite particles (patent document 1), and in addition to this, there is a method of adding a glass component, such as SiO₂、B₂O₃、Na₂A glass component consisting of O, a method of forming liquid phase sintering and promoting the growth of ferrite particles (patent document 2). There is also a method of adding a glass component containing no PbO having a large environmental load, and no Na which decreases the magnetic permeability of ferrite and adversely affects electronic devices, to form liquid phase sintering, thereby promoting the growth of ferrite particles (patent document 3). Further, as an application for RFID, there is a method of controlling the half-value width of the XRD diffraction peak of the crystal phase of the Ni — Zn — Cu-based ferrite powder to increase the magnetic permeability (patent document 4).

Disclosure of Invention

Technical problem to be solved by the invention

In each of patent documents 1to 3, a method of promoting ferrite particle growth by adding a glass component to form liquid phase sintering is adopted. However, these additives are added in an extremely small amount, and are difficult to disperse uniformly, promoting the non-uniform growth of ferrite particles. In patent document 4, although no sintering aid is added, firing at a high temperature of 1060 ℃ or higher is required, and sintering at a low temperature is not considered.

Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide a Ni — Zn — Cu-based ferrite powder which can be sintered at a low temperature.

Technical solution for solving technical problem

The above-described technical problem can be solved by the present invention described below.

That is, the present invention is a Ni — Zn — Cu-based ferrite powder characterized by comprising: containing 49 mol% or less of Fe₂O₃NiO of 5-25 mol%, ZnO of 15-40 mol%, CuO of 5-15 mol% and CoO of 0-3 mol%, wherein the crystallite size is less than 180nm (invention 1).

The present invention also provides the Ni — Zn — Cu-based ferrite powder according to claim 1, wherein the strain is 0.330 or less (invention 2).

The present invention also provides the Ni-Zn-Cu ferrite powder according to claim 1 or 2, wherein the sintered density is 5.00g/cm after firing at 860 ℃ in the air³The above (invention 3).

The present invention also provides a sintered body using the Ni — Zn — Cu-based ferrite powder according to any one of claims 1to 3 (invention 4).

The present invention also provides a ferrite sheet using the Ni — Zn — Cu-based ferrite powder according to any one of claims 1to 3 (invention 5).

Effects of the invention

The Ni-Zn-Cu ferrite powder according to the present invention has a small crystallite size, and therefore, a ferrite sintered body having a high sintered density can be obtained even when sintered at a low temperature. Further, since the Ni — Zn — Cu ferrite powder according to the present invention can be sintered at a low temperature of, for example, 860 ℃, when used in a multilayer inductor in which Ag and magnetic powder are fired simultaneously, diffusion of Ag having a low melting point can be suppressed, and improvement of the inductor performance can be expected.

Detailed Description

The Ni-Zn-Cu based ferrite powder according to the present invention will be described.

The Ni — Zn — Cu-based ferrite powder according to the present invention contains Fe, Ni, Zn, and Cu, and Co as necessary as constituent metal elements. The constituent metal elements are converted into Fe₂O₃NiO, ZnO, CuO and CoO, in the case of Fe₂O₃The total (100%) of NiO, ZnO, CuO and CoO contains 49 mol% or less of Fe₂O₃5-25 mol% of NiO, 15-40 mol% of ZnO, 5-15 mol% of CuO and 0-3 mol% of CoO.

The Fe content of the Ni-Zn-Cu ferrite powder according to the present invention is Fe₂O₃The content is 49 mol% or less in terms of conversion. When the Fe content exceeds 49 mol%, the sinterability is significantly reduced. The content of Fe is preferably 48.9 mol% or less, and more preferably 48.8 mol% or less. The lower limit is about 45 mol%.

The Ni content of the Ni-Zn-Cu ferrite powder according to the present invention is 5 to 25 mol% in terms of NiO. When the Ni content is less than 5 mol%, μ' is decreased, which is not preferable. Further, the curie temperature is lowered, and the usable temperature range is limited, which is not preferable. When the Ni content exceeds 25 mol%, μ' also decreases, which is not preferable. The Ni content is preferably 6 to 24.9 mol%, more preferably 7 to 24.8 mol%.

The Zn content of the Ni-Zn-Cu ferrite powder according to the present invention is 15 to 40 mol% in terms of ZnO. When the Zn content is less than 15 mol%, μ' is decreased, which is not preferable. Further, the curie temperature is lowered, and the usable temperature range is limited, which is not preferable. When the Zn content exceeds 40 mol%, μ' also decreases, which is not preferable. The Zn content is preferably 18 to 38 mol%, more preferably 20 to 35 mol%.

The Cu content of the Ni-Zn-Cu ferrite powder according to the present invention is 5 to 15 mol% in terms of CuO. If the Cu content is less than 5 mol%, the sinterability is lowered, and it is difficult to produce a sintered body at a low temperature. When the Cu content exceeds 15 mol%, μ' is decreased, which is not preferable. The Cu content is preferably 6 to 14 mol%, more preferably 7 to 13 mol%.

The Ni-Zn-Cu ferrite powder according to the present invention may contain Co. The Co content is 0 to 3 mol% in terms of CoO. In the present invention, since the ferrite contains Co, the serpentine critical line is shifted to the high frequency side, and therefore the Q (μ '/μ ") of the ferrite core, which is the ratio of the real part μ' to the imaginary part μ ″ of the complex permeability in the high frequency region, can be increased. When the Co content exceeds 3 mol% in terms of CoO, the magnetic permeability is lowered, and the Q of the ferrite core tends to be lowered. The Co content is preferably 0 to 2.9 mol%, more preferably 0 to 2.8 mol%, and particularly preferably 0.1 to 2.8 mol%.

The crystallite size of the Ni-Zn-Cu ferrite powder according to the present invention is 180nm or less. When the crystallite size exceeds 180nm, grain growth is promoted in the magnetic powder stage, so that sintering properties are lowered when a sintered body or green sheet is fired, and sintering at a low temperature is not possible. More preferably 175nm or less, and still more preferably 170nm or less. The lower limit is about 100 nm. The crystallite size can be determined by the method of the example described later. In particular, the crystallite size can be adjusted by adjusting Fe as an Fe raw material described later₂O₃The BET specific surface area of (B) is adjusted to the above range.

The Ni-Zn-Cu ferrite powder according to the present invention preferably has a crystal strain of 0.330 or less. When the strain exceeds 0.330, μ' may decrease, which is not preferable. More preferably 0.325 or less, and still more preferably 0.320 or less. The lower limit is about 0.100. Among them, the Ni-Zn-Cu-based ferrite powder according to the present invention is preferably a spinel ferrite single phase. The strain of the crystallites can be determined by the method of the example described later. The strain of the crystallites can be adjusted by the pre-firing temperature and the crushing strength of the ferrite powder.

The Ni — Zn — Cu-based ferrite powder according to the present invention may contain various elements at impurity levels in addition to the above elements within a range not affecting the characteristics thereof. It is generally known that: when Bi is added, the sintering temperature of the ferrite is lowered. However, when the dispersion state of Bi is not uniform, the nonuniform growth of particles is promoted during firing, so that Bi is preferably not intentionally added, and Bi is preferably not contained (0 ppm).

The Ni-Zn-Cu ferrite powder according to the present invention,conversion of Si to SiO as an inevitable impurity₂In this case, the upper limit may be 500 ppm. Preferably, Sn or the like (0ppm) is not contained.

The Ni — Zn — Cu-based ferrite powder according to the present invention can be obtained by a general method in which raw materials such as oxides, carbonates, hydroxides, oxalates of the respective elements constituting the ferrite are mixed at a predetermined composition ratio to obtain a raw material mixture, or the respective elements are precipitated in an aqueous solution to obtain a coprecipitate, and the raw material mixture or the coprecipitate is pre-fired in the air at a temperature of 650 to 950 ℃ for 1to 20 hours and then pulverized. The pre-firing temperature is preferably 700-940 ℃. Further, when a laminate of an electrode material such as Ag or Ag-Pd and a ferrite is fired simultaneously, the firing temperature is preferably 900 ℃ or lower, and therefore the pre-firing temperature is preferably lower than this (lower than 900 ℃).

In the present invention, Fe as the raw material of Fe₂O₃BET specific surface area of (2) is preferably 6.0m²More than g. Fe₂O₃BET specific surface area of less than 6.0m²In the case of the powder,/g, the mixing of the respective raw materials becomes uneven, the sinterability as ferrite magnetic powder is lowered, and a high sintered density cannot be obtained at the time of low-temperature sintering. Fe₂O₃The BET specific surface area of (A) is more preferably 6.5 to 40.0m²(ii)/g, more preferably 7.0 to 30.0m²(ii) in terms of/g. Wherein, Fe₂O₃The BET specific surface area of (A) can be determined, for example, by₂O₃The particle size, the firing temperature, the crushing strength and the like are adjusted to control in the synthesis stage of (2).

In the present invention, since no sintering aid is added during the production of the Ni — Zn — Cu-based ferrite powder, the uneven growth of particles can be suppressed.

Next, the Ni-Zn-Cu ferrite sintered body according to the present invention will be described.

The sintered density of the ferrite sintered body is preferably high even when sintered at a low temperature, and is preferably 5.00g/cm when sintered at a low temperature of, for example, about 860 ℃³The above. Sintered densityLess than 5.00g/cm³In the case, sufficient electromagnetic characteristics cannot be obtained, and the mechanical strength of the sintered body is undesirably reduced. The upper limit of the sintered density is 5.40g/cm³Left and right.

The Ni-Zn-Cu ferrite sintered body according to the present invention can be obtained by sintering a molded body or a laminate obtained by molding 0.3 to 3.0 × 10.10 times the Ni-Zn-Cu ferrite powder according to the present invention using a mold at 840 to 1050 ℃ for 1to 20 hours, preferably 1to 10 hours⁴t/m²The pressure of (3) is applied, and the laminate can be obtained by a so-called green sheet method in which green sheets containing the Ni-Zn-Cu ferrite powder according to the present invention are stacked. As the molding method, a known method can be used, and the above powder press molding method or green sheet method is preferable.

When the sintering temperature is less than 840 ℃, the sintered density decreases, so that sufficient electromagnetic characteristics cannot be obtained, and the mechanical strength of the sintered body decreases. When the sintering temperature exceeds 1050 ℃, the sintered body is easily deformed, and it is difficult to obtain a sintered body having a desired shape. In the case of a multilayer chip inductor, for example, since a laminate of an electrode material such as Ag or Ag — Pd and ferrite is fired at the same time, the interface between the electrode and the ferrite reacts (interdiffuses), and the disconnection of the electrode and the original properties of the ferrite deteriorate. The more preferable sintering temperature is 860 to 1040 ℃. Further, when the laminate of the electrode material such as Ag or Ag-Pd and the ferrite is fired simultaneously, the sintering temperature is preferably 900 ℃ or lower, but it is needless to say that the upper limit of the sintering temperature can be 1050 ℃ when the Ni-Zn-Cu based ferrite powder of the present invention is not fired simultaneously with the electrode material such as Ag or Ag-Pd.

The sintered Ni — Zn — Cu ferrite according to the present invention can be used as a magnetic material for multilayer chip inductors, inductor elements, and other electronic components by forming the sintered Ni — Zn — Cu ferrite into a predetermined shape depending on the application.

Next, the green sheet of the present invention will be explained.

The green sheet means: the sheet is obtained by mixing the Ni — Zn — Cu ferrite powder with a binder, a plasticizer, a solvent, and the like to form a coating material, forming the coating material into a film having a thickness of several μm to several hundred μm by a knife coater, and drying the film. The sheets are stacked and then pressed to form a laminate, and the laminate is fired at a predetermined temperature depending on the application to obtain a multilayer chip inductor, an inductance element, and other electronic components.

The green sheet of the present invention contains 2 to 20 parts by weight of a binder and 0.5 to 15 parts by weight of a plasticizer per 100 parts by weight of the Ni-Zn-Cu ferrite powder of the present invention. Preferably, the adhesive composition contains 4 to 15 parts by weight of a binder and 1to 10 parts by weight of a plasticizer. In addition, the solvent may remain due to insufficient drying after film formation. Further, if necessary, a known additive such as a viscosity modifier may be added.

The kind of the binder is polyvinyl butyral, polyacrylate, polymethyl methacrylate, vinyl chloride, polymethacrylate, vinyl cellulose, rosin acid resin, or the like. A preferred bonding material is polyvinyl butyral.

When the binder is less than 2 parts by weight, the green sheet becomes brittle, and the content of more than 20 parts by weight is not necessary for maintaining the strength.

The plasticizer is selected from benzyl n-butyl phthalate, butanediol butyl phthalate, dibutyl phthalate, dimethyl phthalate, polyethylene glycol, phthalate, butyl stearate, and methyl adipate.

When the amount of the plasticizer is less than 0.5 parts by weight, the green sheet becomes hard and cracks are easily generated. When the plasticizer is more than 15 parts by weight, the green sheet becomes soft and is not easy to handle.

In the production of the green sheet of the present invention, 15 to 150 parts by weight of a solvent is used per 100 parts by weight of the Ni-Zn-Cu ferrite powder. When the solvent is outside the above range, a uniform green sheet cannot be obtained, and thus a multilayer chip inductor, an inductance element, and other electronic parts obtained by sintering the green sheet tend to have variations in characteristics.

The solvent is selected from acetone, benzene, butanol, ethanol, methyl ethyl ketone, toluene, propanol, isopropanol, n-butyl acetate, 3-methyl-3-methoxy-1-butanol, etc.

The stack pressure is preferably 0.2 × 10⁴～0.6×10⁴t/m²。

Next, the ferrite sheet according to the present invention will be described.

In the present invention, the Ni — Zn — Cu-based ferrite sintered body can be used in a plate shape to form a ferrite sheet.

The thickness of the plate-like ferrite sintered body of the present invention is preferably 0.01 to 1 mm. More preferably 0.02 to 1mm, and still more preferably 0.03 to 0.5 mm.

In the ferrite sheet according to the present invention, an adhesive layer may be provided on at least one surface of the ferrite sintered plate. The thickness of the adhesive layer is preferably 0.001 to 0.1 mm.

In the ferrite sheet according to the present invention, a protective layer may be provided on at least one surface of the ferrite sintered plate. The thickness of the protective layer is preferably 0.001 to 0.1 mm.

The adhesive layer of the present invention may be a double-sided tape. The double-sided tape is not particularly limited, and a known double-sided tape can be used. The adhesive layer may be one obtained by laminating an adhesive layer, a flexible and stretchable film or sheet, an adhesive layer, and a release sheet in this order on one surface of a ferrite sintered plate.

The protective layer of the present invention can improve the reliability and durability against powder falling when the ferrite sintered plate is divided by providing the protective layer. The protective layer is not particularly limited as long as it is a resin that extends without breaking when the ferrite sheet is bent, and examples thereof include a PET film.

The ferrite sheet according to the present invention may be configured as follows in order to adhere closely to a bent portion and prevent breakage during use: the ferrite sintered plate can be divided by using at least 1 groove provided on at least one surface of the ferrite sintered plate as a starting point. The grooves may be formed continuously or intermittently, or a plurality of minute recessed portions may be formed instead of the grooves. The cross-section of the groove is desirably U-shaped or V-shaped.

In the ferrite sheet according to the present invention, it is preferable that the ferrite sintered plate is divided into small pieces in advance in order to adhere closely to the bent portion and prevent breakage during use. For example, the ferrite sintered plate may be divided in advance using at least 1 groove provided on at least one surface of the ferrite sintered plate as a starting point, or may be divided into small pieces without forming a groove.

The ferrite sintered plate is classified into any size of triangle, quadrangle, polygon or their combination according to the slot. For example, the length of one side of a triangle, a quadrangle, or a polygon is usually 1to 12mm, and when the bonding surface of the adherend is a curved surface, it is preferably 1mm or more and 1/3 or less of the curvature radius thereof, and more preferably 1mm or more and 1/4 or less. When the groove is formed, the flat surface can be adhered or substantially adhered to the cylindrical side curved surface and the surface having some irregularities without being cracked into an irregular shape at a position other than the groove.

The width of the opening of the groove formed in the ferrite sintered plate is preferably 250 μm or less, and more preferably 1to 150 μm. When the width of the opening exceeds 250 μm, the permeability of the ferrite sintered plate is undesirably decreased. The depth of the groove is generally 1/20-3/5 of the thickness of the ferrite sintered plate. Among them, in the case of a thin sintered ferrite plate having a thickness of 0.1mm to 0.2mm, the depth of the groove is preferably 1/20 to 1/4, more preferably 1/20 to 1/6, based on the thickness of the sintered ferrite plate.