JP7565611B2 - Soft magnetic metal flaky powder, resin composite sheet using same, and resin composite composition - Google Patents

Description

Detailed Description of the Invention

The present invention relates to a soft magnetic metal flaky powder used in noise suppression parts used as a countermeasure against unwanted electromagnetic waves in communication devices and various electronic devices, magnetic shield parts used in electromagnetic induction devices, and cores for electronic components such as inductors and reactors, and to a resin composite sheet and a resin composite composition for molding using the same.

Unwanted electromagnetic waves generated by communication devices and various electronic devices can cause equipment malfunctions and communication failures due to external and internal interference, and various countermeasures have been implemented, but as the types of radio waves used increase and frequencies become higher, the types of control ICs and driving frequencies become more diverse, making the problem even more apparent.

In addition, as communication devices and various electronic devices become thinner and smaller, the mounting density of electronic components has increased dramatically, resulting in frequent problems caused by electromagnetic interference between components and circuit boards. To combat this, noise-suppressing electronic components and flexible magnetic sheets (resin composite sheets) are being used.

On the other hand, the effective use of electromagnetic waves is progressing, and pen input and contactless charging for mobile devices that use electromagnetic induction methods have become widespread. In addition, resin composite sheets and molded products are being used as magnetic shielding materials in combination with coil components to prevent interference with metal parts and make effective use of magnetic fields.

Soft magnetic metal flake powder is used in resin composite sheets and molded products used for electromagnetic noise suppression and magnetic shielding. This is because processing into a flake shape reduces the demagnetizing factor, increases the in-plane magnetic permeability, and allows the magnetic permeability to be maintained up to higher frequencies beyond the snake limit. For electromagnetic noise suppression, the imaginary permeability μ'' which indicates the magnetic loss of the magnetic permeability is used, while for magnetic shielding, the real permeability μ' is used.

However, in recent years, with the progress of thinning and miniaturization of devices, the mounting space for electromagnetic noise suppression and magnetic shielding parts has become limited, and there is an increasing demand for resin composite sheets and resin composite compositions for molding using soft magnetic metal flake powders that have high magnetic permeability and low core loss, i.e., so-called high soft magnetic properties. In addition, there is a demand for core materials with high soft magnetic properties for miniaturization, loss reduction, and large current compatibility in electronic components such as inductors and reactors for boost circuits.

Conventionally, it is known that the magnetic permeability of a flat powder of Fe-Al-Si composition called Sendust, which is a soft magnetic metal flat powder using Fe-based alloy powder, is high, and in particular, a composition consisting of Fe and unavoidable impurities at about 5.4 wt% Al and 9.6 wt% Si, where both the crystal magnetic anisotropy and magnetostriction are zero, is excellent. For this reason, there is Patent No. 3722391 (Patent Document 1), which adjusts the composition by taking into account the surface oxidation of the flat powder. On the other hand, Patent No. 6592424 (Patent Document 2) and JP-A-2005-281783 (Patent Document 3) propose that a higher magnetic permeability can be obtained by actively adjusting the composition of Al and Si.

In addition, with regard to nanocrystalline materials that are expected to have high soft magnetic properties exceeding those of sendust, nanocrystalline soft magnetic metal flat powders have been proposed in Japanese Patent No. 2702757 (Patent Document 4) and Japanese Patent Laid-Open No. 11-269509 (Patent Document 5). Furthermore, Japanese Patent Laid-Open No. 2021-111766 (Patent Document 6) proposes an Fe-Al-Si-based soft magnetic metal flat powder that has little change in magnetic permeability and can obtain high magnetic permeability in the temperature range in which various devices actually operate.

Patent No. 3722391 Patent No. 6592424 JP2005-281783 Patent No. 2702757 JP 11-269509 A Patent Publication No. 2021-111766

When communication devices and various electronic devices are actually used, there are changes in the ambient temperature and heat generation, and there is a demand for performance guarantees at -40 to 150°C for automobiles and -40 to 85°C for other devices. For this reason, it is necessary for resin composite sheets and molded products to ensure stable and high electromagnetic noise suppression and magnetic shielding performance, or soft magnetic properties as a core material, at least in the temperature range of -40 to 85°C. In particular, in non-contact power supply using electromagnetic induction, heat is generated in the module due to magnetic losses in the battery during charging and in coil components including magnetic materials, so if the performance of the magnetic shielding material decreases due to temperature rise, magnetic losses increase, which further increases the temperature and reduces performance, resulting in a vicious cycle that reduces charging efficiency.

However, soft magnetic properties including magnetic permeability are generally measured only at room temperature, and there is no description of obtaining stable magnetic permeability in the actual operating temperature range as referred to in the present invention in Patent Documents 1, 2, 3, 4, and 5. Furthermore, compared with ferrite sintered bodies used for NFC and contactless charging, or pre-cracked ferrite sheets, amorphous sheets, nanocrystalline metal sheets, etc., the magnetic permeability is insufficient and the magnetic shielding performance is insufficient.

In addition, Patent Documents 4 and 5 state that high soft magnetic properties can be obtained by using a nanocrystalline soft magnetic metal flat powder that is processed into a flat shape using powder obtained by crushing an Fe-based amorphous ribbon after embrittlement treatment and then nanocrystallizing the powder, but Patent Document 4 focuses on the coercive force and saturation magnetic flux density, and does not state anything about the magnetic permeability. In addition, the D50 average particle size is small, and the aspect ratio is also low. Patent Document 5 does not state anything about the coercive force, and it cannot be said that the magnetic permeability is sufficiently high.

Furthermore, there is a demand for resin composite sheets that have low core loss while maintaining magnetic permeability, and that have high flexibility and thin-walled products, as well as products with higher magnetic permeability and low core loss. In order to realize a thin-walled product with high flexibility, it is necessary to reduce the powder blending amount by using nanocrystalline soft magnetic metal flat powder that has high soft magnetic properties even with a small particle size. Furthermore, in order to respond to high magnetic permeability, it is necessary to significantly improve the soft magnetic properties of the nanocrystalline soft magnetic metal flat powder. However, it is difficult to achieve both of these, and it is necessary to provide a resin composite sheet that has characteristics in either flexibility or magnetic permeability by optimally nano-crystallizing the nanocrystalline soft magnetic metal flat powder, adjusting the particle size and aspect ratio, and suppressing the coercive force. In addition, there is a demand for thinning and high magnetic permeability in resin composite compositions for molding processing, and it is necessary to provide a resin composite composition that can respond to thinning while maintaining magnetic permeability and having low core loss, and a resin composite composition that has higher magnetic permeability and low core loss.

The present invention has been made to solve the above problems, and aims to provide a nanocrystalline soft magnetic metal flaky powder having a small change in the temperature coefficient of magnetic permeability within the range of -40°C to 150°C when used in a resin composite sheet or a resin composite composition molded product, and having high magnetic permeability and low core loss, and a resin composite sheet using the material and having high magnetic permeability and low core loss, as well as a resin composite composition for molding.

The present invention aims to solve the problems associated with the above-mentioned conventional soft magnetic metal flaky powder, the resin composite sheet using said material, and the resin composite composition for molding.

According to the present invention, the nanocrystalline soft magnetic metal flaky powder has a particle size of 5 nm to less than 30 nm, a crystallinity of 65% to less than 95%, and an aspect ratio of 20 to less than 80 in a powder with a particle size near the average particle size D50, and a coercive force of 20 A / m to less than 150 A / m. The nanocrystalline soft magnetic metal flaky powder is characterized in that the temperature coefficient of magnetic permeability Kn (n is 1, 2, 3) of a resin composite sheet or a molded resin composite composition using the nanocrystalline soft magnetic metal flaky powder is represented by the following formulas (1) (2) and (3) in the range of -40 ° C. to 150 ° C. or less, and is in the range of 0 ≦ K1 ≦ 0.20, -0.10 ≦ K2 ≦ 0.10, and -0.15 ≦ K3 ≦ 0.05.
K1=(μ(0℃)−μ(−40℃))/μ(−40℃) (1)
K2=(μ(85℃)−μ(−40℃))/μ(−40℃) (2)
K3=(μ(150℃)−μ(−40℃))/μ(−40℃) (3)
μ: magnetic permeability (μ': real magnetic permeability, μ”: imaginary magnetic permeability), μ (0℃): magnetic permeability at 0℃

According to the present invention, the nanocrystalline, soft magnetic metal flaked powder has an average particle size D50 of 20 μm to less than 40 μm, an average thickness around the D50 average particle size of 0.2 μm to less than 1.5 μm, and a resin composite sheet using the nanocrystalline, soft magnetic metal flaked powder has a coercive force of 20 A/m to less than 100 A/m.

According to the present invention, the nanocrystalline soft magnetic metal flaked powder has an average particle size D50 of 40 μm to less than 100 μm, an average thickness around the D50 average particle size of 1.5 μm to less than 5 μm, and a resin composite sheet using the nanocrystalline soft magnetic metal flaked powder has a coercive force of 20 A/m to less than 80 A/m.

According to the present invention, there is provided a resin composite sheet which is made of the nanocrystalline soft magnetic metal flaky powder and a resin, has a coercive force of 20 A/m to less than 100 A/m, and has a core loss of 50 kW/m ³ to less than 300 kW/m ³ when measured under conditions of Bm and frequency of 50 mT-100 kHz using a stack of three ring-shaped samples each having an outer diameter of 20 mm, an inner diameter of 10 mm, and a thickness of 0.15 mm.

According to the present invention, there is also obtained a resin composite composition for molding, which is characterized in that the core loss measured under conditions of Bm and frequency of 50 mT-100 kHz is 100 kW/m ³ to less than 600 kW/m ³ when the resin is molded into an outer diameter of 12.8 mm, an inner diameter of 7.5 mm, and a thickness of 5 mm, and the resin composite composition is made of the nanocrystalline soft magnetic metal flat powder and a resin.

The present invention provides a nanocrystalline soft magnetic metal flaky powder having a small change in the temperature coefficient of magnetic permeability within the range of -40°C to 150°C when used in a resin composite sheet or a resin composite composition molded product, and having high magnetic permeability and low core loss, as well as a resin composite sheet using the material and having high magnetic permeability and low core loss, and a resin composite composition for molding.

FIG. 13 shows a method for calculating the degree of crystallinity by a profile fitting method using the peak of bcc Fe(110) near 2θ=45° obtained by orienting nanocrystalline metal flaky powder so that it is parallel to the measurement surface and measuring it by XRD using a Cu tube. 1 is a graph showing the temperature dependence of magnetic permeability of resin composite sheets using flat soft magnetic metal powders of Examples 4 and 9 and Comparative Examples 10 and 11.

The best mode of the present invention will now be described in detail.

The amorphous alloy that is the raw material for nanocrystalline soft magnetic metal flaky powder can be produced by a rapid cooling method such as the single roll method, the twin roll method, or the melt spin method.

The amorphous alloy is an Fe-based alloy, and for example, an alloy having an Fe-Si-B-Nb-Cu composition or an Fe-Si-B-P-Cu composition can be used. If necessary, the alloy may contain trace components such as Cr, W, Ta, Hf, Ti, Ni, and C. However, there are no particular limitations on the composition as long as a nanocrystalline phase can be obtained by the crystallization treatment.

When using a metal foil strip obtained by a single roll method, a twin roll method, a melt spin method, etc., it is difficult to crush the metal foil strip to obtain a raw material for flattening as it is. In addition, in order to obtain a raw material powder having the desired processability, embrittlement treatment is performed at a temperature exceeding 200°C and below the nanocrystallization temperature in air or nitrogen gas atmosphere, inert gas atmosphere, or vacuum, and then the material is crushed with a ball mill, vibration mill, pin mill, hammer mill, etc. to obtain a raw material powder for flattening of a predetermined particle size. However, if embrittlement progresses during the manufacturing process of the metal foil strip, embrittlement treatment is not particularly necessary and the material may be crushed as it is. In addition, if flattening can be performed in the state of the metal foil strip, embrittlement treatment and crushing can be omitted.

The flattening process is not particularly limited, but can be carried out in the presence of distilled water or an organic solvent using an attritor, ball mill, vibration mill, etc. As the organic solvent, toluene, hexane, alcohol, ethylene glycol, etc. can be used, and the atmosphere inside the device may be adjusted during processing. Stearic acid, etc. may also be added as a flattening aid.

After the flattening process, the amorphous alloy flat powder is heat-treated in a nitrogen gas atmosphere, an inert gas atmosphere, or in a vacuum at a temperature above the crystallization temperature to generate a nanocrystalline phase. The heat treatment device and conditions are not particularly limited as long as the flat powder breaks down and becomes smaller in diameter due to the volumetric shrinkage associated with nanocrystallization, and the desired crystal grain size and degree of crystallinity can be achieved.

It is desirable that the aspect ratio of the nanocrystalline soft magnetic metal flat powder in the powder having an average particle size of about D50 is 20 to less than 80, and the coercive force is 20 A/m to less than 150 A/m. If the aspect ratio is less than 20, the demagnetizing factor becomes large, and if it is 80 or more, the processability decreases. However, even if the aspect ratio is less than 20 to 80, if the proportion of fine powder increases, the coercive force becomes 150 A/m or more, and the magnetic permeability of the resin composite sheet and molded product decreases. For this reason, the coercive force may be adjusted by removing the fine powder by air classification or the like.

The average particle diameter D50 of the nanocrystalline soft magnetic metal flat powder was measured using R4 with HELOS/BR-multi manufactured by Sympatec. Flat powders having a particle diameter range of ±10% of the obtained average particle diameter D50 were extracted by air classification, embedded in epoxy resin and mirror polished to obtain a sample for thickness measurement. The aspect ratio is expressed as diameter/thickness because the flat powder is generally disc-shaped, but the diameter is the value of the average particle diameter D50, and the thickness of the flat powder was measured with a scanning electron microscope to obtain the aspect ratio. The aspect ratio may be obtained by embedding a resin composite sheet or molded product in epoxy resin, measuring the average length and thickness with a scanning electron microscope, and correcting the length to the diameter.

The magnetic permeability was measured in a thermostatic chamber at a temperature range of -40°C to 150°C using an impedance analyzer E4991B, a magnetic material test fixture 16454A, and a heat resistance test kit manufactured by Keysight. The measurement samples used were made by molding a resin composite sheet and a resin composite composition. The measurement sample for the resin composite sheet was made by punching a ring-shaped sample with an outer diameter of 20 mm and an inner diameter of 10 mm from a sheet with a thickness of 0.15 mm. The molded product used was a sample with an outer diameter of 20 mm and an inner diameter of 20 mm and a thickness of 0.6 mm. The shape of the sample for measuring the magnetic permeability is not particularly limited as long as the magnetic permeability can be measured. Furthermore, the measurement may be performed in the state of the resin composite sheet or the molded product, or in the state of powder, using a vibration sample magnetometer (VSM), a BH analyzer, an LCR meter, or the like.

The coercive force was measured using an automatic coercive force meter K-HC1000 manufactured by Tohoku Special Steel Co., Ltd., with an applied magnetic field of 148 kA/m. Approximately 10 mg of the flat powder was covered with non-magnetic tape to prevent scattering, and used as a measurement sample. A sample for magnetic permeability measurement was used to measure the coercive force of the resin composite sheet and the molded product of the resin composite composition. Coercive force may also be measured using a vibrating sample magnetometer (VSM), BH analyzer, etc.

The crystal grain size of the nanocrystalline particles of the nanocrystalline soft magnetic metal flat powder is desirably 5 nm to less than 30 nm, and more preferably 5 nm to less than 25 nm. If the crystal grain size is less than 5 nm, the nanocrystalline particle growth is insufficient, resulting in poor soft magnetic properties, and if it is 30 nm or more, the responsiveness of the crystal grains to an AC magnetic field decreases, resulting in poor soft magnetic properties. In addition, the crystallinity is desirably 65% to less than 95%, and more preferably 65% to less than 90%. If the crystallinity is less than 65%, the crystal grain generation is insufficient, and if it is 95% or more, the crystal grains become coarse, resulting in poor soft magnetic properties.

The crystal grain size of the nanocrystalline particles was determined by orienting the flat surface of the nanocrystalline metal powder so that the plane was generally parallel to the measurement surface, and using the peak of bcc Fe (110) near 2θ = 45 ° from the results of XRD measurement using a Cu tube with a powder X-ray diffraction device MiniFlex 600 manufactured by Rigaku Co., Ltd. The crystallinity was calculated from the XRD measurement results by a profile fitting method using a SmartLab Studio II application analysis package manufactured by Rigaku Co., Ltd. For the calculation, the area of the diffraction peak before and after nanocrystallization of bcc Fe (110) was used, as shown in FIG. 1. It is difficult to measure the crystallinity precisely, and the apparent crystallinity obtained simply from the XRD measurement results was taken as the crystallinity. Samples for XRD measurement do not have to be powders; sheets and molded articles can be placed in a folder so that the flat surfaces of the nanocrystalline metal powder are generally parallel to the measurement surface.

The nanocrystalline soft magnetic metal flake powder desirably has an average particle diameter D50 of 20 μm to less than 40 μm. If it is less than 20 μm, it becomes difficult to obtain a sufficiently high magnetic permeability because the amount of fine powder with high coercive force increases. If it is 40 μm or more, the flexibility of the resin composite sheet decreases. In addition, it is desirable that the average thickness near the D50 average particle diameter is 0.2 μm to less than 1.5 μm. If it is less than 0.2 μm, the specific surface area becomes too high, so the processability decreases, and if it is 1.5 μm or more, the aspect ratio becomes small, and the magnetic permeability decreases due to the increase in the demagnetizing field coefficient. It is desirable that the coercive force of the resin composite sheet using the nanocrystalline soft magnetic metal flake powder is 20 A/m to less than 100 A/m. If the coercive force is 100 A/m or more, the magnetic permeability decreases.

The nanocrystalline soft magnetic metal flat powder desirably has an average particle diameter D50 of 40 μm to less than 100 μm. If it is less than 40 μm, the requirement for particularly high magnetic permeability cannot be met, and if it is 100 μm or more, the processability decreases. Furthermore, the coarse flat powder contains internal cracks, which become magnetic gaps and lead to a decrease in soft magnetism, so they may be removed by air classification or mechanical sieving. In addition, it is desirable that the average thickness near the D50 average particle diameter is 1.5 μm to less than 5 μm. If it is less than 1.5 μm, the amount of fine powder with high coercive force increases, and if it is 5 μm or more, the demagnetizing factor increases and the magnetic permeability decreases. It is desirable that the coercive force of the resin composite sheet using the nanocrystalline soft magnetic metal flat powder is 20 A/m to less than 80 A/m. If it is 80 A/m or more, the magnetic permeability decreases.

Furthermore, the bulk density/true density is preferably in the range of 0.034 to 0.076. If it is less than 0.034, the flattening will progress too much, making handling difficult, and the coercive force will increase due to an increase in over-pulverized fine powder and an uneven contour, resulting in a decrease in magnetic permeability. On the other hand, if it exceeds 0.076, the flattening will be insufficient, resulting in a decrease in magnetic permeability. The bulk density was measured based on JIS Z2504. The true density was measured using an AccuPyc1330 manufactured by Shimadzu Corporation.

The resin composite sheet is prepared by mixing nanocrystalline soft magnetic metal flaky powder and polymeric material in a predetermined ratio, forming it into an ink-like form using various known methods, and then producing a sheet-like product by doctor coating, comma coating, screen printing, etc., which may be further compressed using various rolls or presses. Alternatively, the resin composite sheet may be produced by kneading the mixture using a kneader or the like and then rolling it, and then compressing the mixture using a press, but the method for producing the resin composite sheet is not limited to these. When producing the sheet, a magnetic field is applied to control the orientation of the nanocrystalline soft magnetic metal flaky powder, thereby increasing the magnetic permeability.

As the polymer resin, polyurethane, acrylic, silicon, epoxy, chlorinated polyethylene, chloroprene rubber, etc. can be used alone or in combination, but there is no particular limitation, and it is desirable that the resin has a heat resistance of 150°C. There is also no particular limitation on the thermoplasticity and thermosetting properties. In addition, various surface treatments using coupling agents, dispersants, rust inhibitors, etc., and various additives such as antioxidants, pigments, non-magnetic fillers, and thermally conductive fillers can be added as necessary within a range that does not impair the object of the present invention.

The resin composite sheet desirably has a coercive force of 20 A/m to less than 100 A/m, more preferably less than 80 A/m. If it is 100 A/m or more, the magnetic permeability decreases. Also, the core loss is desirably 50 kW/m ³ to less than 300 kW/m ³ , more preferably less than 200 kW/m ^3. If the core loss is 300 kW/m ³ or more, when it is used in the magnetic parts of various electronic components, the magnetic loss increases and the component performance decreases. Also, when it is used as a magnetic shield material for non-contact charging, the decrease in charging efficiency due to magnetic loss and the accompanying heat generation become a major problem. It is desirable that the content of the nanocrystalline soft magnetic metal flake powder is 35 vol% to less than 65 vol% with respect to the total solid content. More preferably, it is 40 vol% to less than 55 vol%. If it is less than 35 vol%, the magnetic permeability will be low even if the coercive force is less than 100 A/m, and if it is 65 vol% or more, it becomes difficult to form it into a sheet, and the magnetic permeability decreases.

The core loss was measured for the resin composite sheet and the molded product of the resin composite composition using a BH analyzer SY-8219 manufactured by Iwasaki Electric Co., Ltd. and a high-speed bipolar power supply HSA4041 manufactured by NF Corporation. The measurement sample for the resin composite sheet was made by punching out a ring-shaped sample with an outer diameter of 20 mm and an inner diameter of 10 mm from a sheet with a thickness of 0.15 mm, stacking three of these, sandwiching them between non-magnetic resin plates, and winding a wire of φ0.26 mm around them. The primary side had 19 turns and the secondary side had 5 turns. The molded products were prepared as samples with an outer diameter of 20 mm, an inner diameter of 10 mm, and a thickness of 0.6 mm, and samples with an outer diameter of 12.8 mm, an inner diameter of 7.5 mm, and a thickness of 5 mm. The sample with an outer diameter of 20 mm had 19 turns on the primary side and 5 turns on the secondary side, and the sample with an outer diameter of 12.8 mm had 15 turns on the primary side and 5 turns on the secondary side to prepare measurement samples. The measurements were performed at room temperature of 25°C, with Bm and frequency of 50 mT-100 kHz.

The resin composite composition is obtained by mixing nanocrystalline soft magnetic metal flaky powder with a polymer resin and kneading it with a kneader or a twin-screw kneader, but is not limited to these, and can be produced by various known methods. The content of the nanocrystalline soft magnetic metal flaky powder relative to the total solid content is desirably 35 vol% to less than 65 vol%, and more desirably 40 vol% to less than 60 vol%. If it is less than 35 vol%, the magnetic permeability of the molded product will be low, and if it is 65 vol% or more, molding will be difficult and the magnetic permeability will decrease. In addition, the core loss is desirably 100 kW/m ³ to less than 600 kW/m ³ , and more desirably less than 400 kW/m ^3.

The resin composite composition can be molded into various shapes using, but not limited to, an extrusion molding machine, an extrusion molding machine, a compression molding machine, etc. During molding, a magnetic field may be applied to orient the flat powder.

The present invention will now be described in more detail with reference to examples.

To prepare the nanocrystalline soft magnetic metal flat powder used in Examples 1 to 12 and Comparative Examples 1 to 4 and 6 to 9 , an amorphous ribbon having a thickness of 20 μm and a composition of Fe _83.3 Si _7.7 B _2.0 Nb _5.7 Cu _1.3 (wt%) prepared by a single roll method was used as the starting material. This was embrittled for 1 hour in an Ar atmosphere at 420 ° C for Examples 1 to 5 and Comparative Examples 1 to 4 , and at 220 ° C for Examples 6 to 12 and Comparative Examples 6 to 9 , and then pulverized to 74 μm or less in a ball mill. The pulverized powder was then flattened under wet conditions using ethanol in an attritor. Further, nanocrystallization was performed for 1 hour at 560 ° C in an Ar atmosphere.

In Examples 1 to 12, Comparative Examples 1 to 4, and Comparative Examples 6 to 9, the obtained nanocrystalline soft magnetic metal flat powder was used, and a thermosetting acrylic rubber mixed resin with a heat resistance of 150°C was mixed with toluene and dispersed in a resin solution diluted with toluene so that the total solid content was 50 vol%. A coating material for coating was prepared by applying this coating material to a thickness of 0.05 mm with a comma coater, performing magnetic field orientation, and then drying at 50°C to remove the solvent. Six sheets after drying were laminated and hot pressed at 150°C with a pressure of 10 MPa to obtain a resin composite sheet for performance evaluation with a thickness of 0.15 mm. Next, the sheet was punched out into a doughnut shape with an outer diameter of 20 mm and an inner diameter of 10 mm, and the magnetic permeability, coercive force, and core loss were measured. The real part (μ') of the magnetic permeability at each temperature was measured at 1 MHz, and the imaginary part (μ'') was measured at 10 MHz.

In Comparative Examples 5 and 10, alloy powder with a composition of Fe _84.8 Al _5.6 Si _9.6 (wt%) produced by gas atomization was used as the starting material, and in Comparative Example 11, alloy powder with a composition of Fe _84.0 Al _7.0 Si _9.0 (wt%) was used as the starting material. The powder was flattened in an attritor under wet conditions using ethanol, and then heat-treated at 700°C in an Ar atmosphere for 1 hour. A resin composite sheet was produced using this flattened powder and a thermosetting acrylic rubber-based mixed resin with a heat-resistant temperature of 150°C, and the magnetic permeability, coercive force, and core loss were measured. The real part (μ') of the magnetic permeability at each temperature was measured at 1 MHz, and the imaginary part (μ'') was measured at 10 MHz.

Table 1 shows Examples 1 to 5 and Comparative Examples 1 to 5. In Examples 1 to 5, the flexibility of the resin composite sheet was emphasized, and the flattening conditions were adjusted so that the average particle size of the nanocrystalline metal flat powder was 20 μm to less than 40 μm, the average thickness was 0.2 to less than 1.5 μm, and flattened powder with a predetermined bulk density/true density was obtained after nanocrystallization. Furthermore, in the flattening process, the flattening conditions such as the slurry concentration and the collision energy of the grinding media were optimized so that the coercive force after the nanocrystallization process was minimized, the generation of fine powder was suppressed, and the contour of the flattened powder was smooth. At the same time, controlled moderate microcracks were introduced into the surface of the flattened powder.

Table 2 shows Examples 6 to 12 and Comparative Examples 6 to 11. In Examples 6 to 12, the magnetic permeability of the resin composite sheet was emphasized, and the flattening conditions were adjusted so that the average particle size of the nanocrystalline soft magnetic metal flat powder was 40 μm to less than 100 μm, the average thickness was less than 1.5 to 5 μm, and flat powder with a predetermined bulk density/true density was obtained after nanocrystallization. Furthermore, in the flattening process, the flattening conditions such as the slurry concentration and the collision energy of the grinding media were optimized so that the coercive force after the nanocrystallization process was minimized, the generation of fine powder was suppressed, and the outline of the flat powder was smooth. At the same time, moderate microcracks were introduced into the surface of the flat powder. In Examples 8 to 10, 5 wt% of fine powder with high coercive force and coarse flat powder with internal cracks that become magnetic gaps and affect the soft magnetic properties were removed by air classification.

Table 3 shows Examples 13 and 14, and Comparative Examples 12 and 13. For Examples 13 and 14 and Comparative Examples 12 and 13, the nanocrystalline soft magnetic metal flat powder of Example 4 and the soft magnetic metal flat powder of Comparative Example 10 having a composition of Fe _84.8 Al _5.6 Si _9.6 (wt%) were used. This metal flat powder was surface-treated with a silane coupling agent, mixed with heat-resistant nylon (PA-9T), and heated and kneaded using a twin-screw kneader to obtain a resin composite composition. Next, a plate-shaped molded product having a thickness of 0.6 mm was produced using an injection molding machine, and the magnetic permeability and coercive force were measured using a sample punched to a thickness of 0.6 mm with an outer diameter of 20 mm and an inner diameter of 10 mm. The sample shape was set to Shape 1, and in order to measure the core loss in a state in which the orientation of the nanocrystalline soft magnetic metal flat powder was disturbed, a ring-shaped molded product having an outer diameter of 12.8 mm, an inner diameter of 7.5 mm, and a thickness of 5 mm was prepared as Shape 2. A winding was applied to samples of Shape 1 and Shape 2, and the core loss was measured under the conditions of Bm and frequency of 50 mT-100 kHz.

From Table 1, in all of Examples 1 to 5, the temperature coefficient K of real (1 MHz) and imaginary permeability (10 MHz) satisfies 0≦K1≦0.20, -0.10≦K2≦0.10, -0.15≦K3≦0.05 in the range of -40 ° C to 150 ° C, and the effect of the measurement temperature on the permeability is minor. In addition, it has a higher real and imaginary permeability at 0 ° C than Comparative Examples 1 to 4 , and the core loss is low in both cases. In the metal flat powder using the alloy powder of Fe _84.8 Al _5.6 Si _9.6 (wt%) composition produced by the gas atomization method of Comparative Example 5, the permeability is maximum at 0 ° C, and the decrease in permeability at 85 ° C and 150 ° C is remarkable. Furthermore, the permeability at 0 ° C is significantly insufficient, and the core loss is high.

From Table 2, in all of Examples 6 to 12, the temperature coefficient K of real (1 MHz) and imaginary permeability (10 MHz) satisfies 0≦K1≦0.20, -0.10≦K2≦0.10, -0.15≦K3≦0.05 in the range of -40 ° C to 150 ° C, and the effect of the measurement temperature on the permeability is minor. In addition, the real and imaginary permeabilities at 0 ° C are significantly higher than those of Comparative Examples 6 to 9, and the core loss is low. In particular, the permeability of Examples 8 to 10, in which fine powder and coarse flat powder were removed by air classification, shows an extremely high value. In the metal flat powder using the alloy powder of Fe _84.8 Al _5.6 Si _9.6 (wt%) composition produced by the gas atomization method of Comparative Example 10, the permeability is maximum at 0 ° C, and the decrease at 85 ° C and 150 ° C is remarkable. Furthermore, the permeability at 0 ° C is insufficient, and the core loss is high. In the case of the metal flake powder using the alloy powder having a composition of Fe _84.0 Al _7.0 Si _9.0 (wt %) in Comparative Example 11, the temperature dependence of the magnetic permeability is smaller than that of Comparative Example 10, but the decrease in magnetic permeability becomes significant above 85° C., the magnetic permeability at 0° C. is also insufficient, and the core loss is high.

As shown in Fig. 2, the real permeability (1 MHz) of Examples 4 and 9 shows a maximum value near 0°C, but the temperature change of the permeability is smaller and the value is higher than that of Comparative Examples 10 and 11. In particular, Example 9 has a significantly high permeability in the temperature range of -40°C to 150°C. Furthermore, despite the small particle size, Example 10 has a higher permeability than Comparative Examples 10 and 11, and the amount of flat powder blended to achieve the same permeability can be reduced, making it possible to reduce the thickness of the resin composite sheet and improve its flexibility.

From Table 3, in both Examples 13 and 14, the temperature coefficient K of real (1 MHz) and imaginary permeability (10 MHz) satisfies 0≦K1≦0.20, -0.10≦K2≦0.10, -0.15≦K3≦0.05 in the range of -40°C to 150°C, and the effect of the measurement temperature on the permeability is minor. In addition, it has a higher real and imaginary permeability at 0°C than Comparative Example 12, and even in Example 14, which has a large powder blend amount, it has better moldability than Comparative Example 12. This makes it easier to make the molded product thinner. Comparative Example 12 shows a maximum permeability at 0°C, and the permeability drops significantly as the temperature rises. Comparative Example 13 could not be molded because the powder blend amount was too large, and it was not possible to measure. In the case of the nanocrystalline soft magnetic metal flat powder having a highly oriented shape 1 and a randomly oriented shape 2, the core loss is lower for shape 1 than for shape 2, but Examples 13 and 14 show values that are significantly lower than Comparative Example 12.

Claims (6)

A nanocrystalline soft magnetic metal flat powder having an Fe-Si-B-Nb-Cu composition or an Fe-Si-B-P-Cu composition, in which the particle size of the nanocrystalline particles is 5 nm to less than 30 nm and the crystallinity is 65% to less than 95%, and the aspect ratio of the powder having a particle size around the average particle size D50 is 20 to less than 80, the bulk density/true density is 0.034 to 0.076, and the coercive force is 20 A/m to less than 150 A/m. Furthermore, the temperature coefficient Kn (n is 1, 2, 3) of the magnetic permeability of a resin composite sheet or a molded product of a resin composite composition using the nanocrystalline soft magnetic metal flat powder is represented by the following formulas (1), (2), and (3) in the range of -40 ° C. to 150 ° C. or less, and is in the range of 0 ≦ K1 ≦ 0.20, -0.10 ≦ K2 ≦ 0.10, and -0.15 ≦ K3 ≦ 0.05.
K1=(μ(0℃)−μ(−40℃))/μ(−40℃) (1)
K2=(μ(85℃)−μ(−40℃))/μ(−40℃) (2)
K3=(μ(150℃)−μ(−40℃))/μ(−40℃) (3)
μ: magnetic permeability (μ': real magnetic permeability, μ”: imaginary magnetic permeability), μ (0℃): magnetic permeability at 0℃ The nanocrystalline soft magnetic metal flaky powder according to claim 1, characterized in that the average particle diameter D50 is 20 μm to less than 40 μm, the average thickness around the D50 average particle diameter is 0.2 μm to less than 1.5 μm, and the coercive force of a resin composite sheet using the nanocrystalline soft magnetic metal flaky powder is 20 A/m to less than 100 A/m. The nanocrystalline soft magnetic metal flaky powder according to claim 1, characterized in that the average particle diameter D50 is 40 μm to less than 100 μm, the average thickness around the average particle diameter D50 is 1.5 μm to less than 5 μm, and the coercive force of a resin composite sheet using the nanocrystalline soft magnetic metal flaky powder is 20 A/m to less than 80 A/m. A method for producing a nanocrystalline soft magnetic metal flaky powder according to any one of claims 1 to 3,
A step of subjecting a raw material Fe-based amorphous alloy foil strip to an embrittlement treatment at a temperature equal to or lower than a nanocrystallization temperature;
A step of pulverizing the embrittlement treatment to obtain a raw material powder for flattening;
A step of performing a flattening process in the presence of distilled water or an organic solvent, and introducing microcracks into the surface of the raw material powder for flattening during the flattening process;
This method for producing nanocrystalline soft magnetic metal flat powder is characterized by the steps of: heat-treating the flat powder obtained after the flattening process at a temperature above the crystallization temperature in a nitrogen gas atmosphere, an inert gas atmosphere, or a vacuum to generate a nanocrystalline phase; and causing the flat powder to self-break and become smaller in diameter due to the volumetric shrinkage associated with nanocrystallization. A resin composite sheet comprising the nanocrystalline soft magnetic metal flaky powder according to any one of claims 1 to 3 and a resin, characterized in that the coercive force is 20 A/m to less than 100 A/m, and further, when a measurement sample of the resin composite sheet is prepared by stacking three ring-shaped samples each having an outer diameter of 20 mm, an inner diameter of 10 mm, and a thickness of 0.15 mm, and the measurement sample is measured under the conditions of Bm and a frequency of 50 mT-100 kHz, the core loss is 50 to less than 300 kW/ ^m3 . A resin composite composition for molding, comprising the nanocrystalline soft magnetic metal flaky powder according to any one of claims 1 to 3 and a resin, and characterized in that the core loss measured under conditions of Bm and frequency of 50 mT-100 kHz using a molded product having an outer diameter of 12.8 mm, an inner diameter of 7.5 mm, and a thickness of 5 mm is 100 to less than 600 kW/ ^m3 .