Magnetic material and inductor

Abstract

To provide a magnetic material and an inductor, improved in Hsat20 while suppressing deterioration of a μ value.SOLUTION: A magnetic material 1 includes: a first metal magnetic particle MP1; a second metal magnetic particle MP2 having a median particle size larger than that of the first metal magnetic particle MP1; and a resin. The first metal magnetic particle MP1 is covered with a first insulating film IM1. The second metal magnetic particle MP2 is covered with a second insulating film IM2. Both of 2.5≤(T1 / D1) / (T2 / D2)≤3.9 and T2≤39.4 nm are satisfied, where D1 is a median particle size of the first metal magnetic particle MP1, T1 is an average thickness of the first insulating film IM1, D2 is the median particle size of the second metal magnetic particle MP2, and T2 is an average thickness of the second insulating film IM2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a magnetic material and an inductor.

Background Art

[0002] In recent years, with the high-density mounting and high-speed processing of electronic devices, miniaturization and high output of inductors have been required. When attempting to miniaturize an inductor, the volume of the core including the magnetic material of the inductor decreases, which easily leads to a decrease in inductance (L value) and / or deterioration of DC superposition characteristics.

[0003] Patent Document 1 describes a metal powder having a particle size distribution obtained by blending two groups of particles having different average particle sizes, a core (magnetic molded body) manufactured using this metal powder, and an inductor manufactured using this core.

[0004] According to Patent Document 1, by filling voids formed between large particles with small particles, the packing ratio of soft magnetic particles combining large and small particles is increased, and high magnetic permeability and good DC superposition characteristics can be obtained.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the inductor described in Patent Document 1, magnetic flux tends to concentrate on large particles, and there is a tendency to reduce H sat20 (deteriorate DC superposition characteristics). Note that H as used in this specification sat20 refers to calculating the μ value when the direct current is 0, and the current value I when the μ value has decreased by 20% from the μ value sat20It is intended for the magnetic field when the μ value decreases by 20%, which is calculated based on the dimensions of the magnetic molded body and the number of turns of the copper wire.

[0007] H sat20 To improve it, it is conceivable to reduce the ratio of large particles. However, there is a problem that the μ value of the entire molded body (magnetic body) decreases due to the deterioration of the occupancy rate (filling rate) of the magnetic material and the decrease of large particles with a high μ value.

[0008] This disclosure has been made in view of such problems. That is, the main object of this disclosure is to provide a magnetic body and an inductor with improved H while suppressing a decrease in the μ value. sat20

Means for Solving the Problems

[0009] The magnetic body of this disclosure includes first metal magnetic particles, second metal magnetic particles having a larger median particle diameter than the first metal magnetic particles, and a resin, the first metal magnetic particles are coated with a first coating film, the second metal magnetic particles are coated with a second coating film, when the median particle diameter of the first metal magnetic particles is D1, the average thickness of the first coating film is T1, the median particle diameter of the second metal magnetic particles is D2, and the average thickness of the second coating film is T2, 2.5 ≤ (T1 / D1) / (T2 / D2) ≤ 3.9 T2 ≤ 39.4 nm both are satisfied.

[0010] The inductor of this disclosure includes the above-described magnetic body.

Advantages of the Invention

[0011] According to the magnetic body of this disclosure, it is possible to improve H while suppressing a decrease in the μ value. sat20

Brief Description of the Drawings

[0012]

Figure 1

Figure 2A

Figure 2B

Figure 3

Figure 4A

Figure 4B

Figure 5A

Figure 5B

Figure 5C

Figure 6

Figure 7

Figure 8

DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, the magnetic material and the inductor of the present disclosure will be described. Note that the present disclosure is not limited to the following configurations, and may be appropriately changed without departing from the gist of the present disclosure. Also, combinations of a plurality of the individual preferred configurations described below are also within the scope of the present disclosure.

[0014] The drawings shown below are schematic diagrams, and their dimensions, scales of aspect ratios, etc. may be different from those of actual products.

[0015] [Magnetic Material] Hereinafter, the magnetic material of the present disclosure will be described. As used herein, the "magnetic material" broadly refers to materials used to enhance the magnetic field in devices that generate magnetic fields such as inductors. Narrowly, it refers to the coating of the coil (conductive wire) in an inductor and materials used for the core of the coil.

[0016] The magnetic material 1 of the present disclosure includes first metal magnetic particles MP1, second metal magnetic particles MP2 having a median particle size larger than that of the first metal magnetic particles MP1, and a resin R.

[0017] - First metal magnetic particles - For the first metal magnetic particles MP1, Fe-based metal magnetic particles may be used. For example, crystalline powders may be used. Examples of the crystalline powder include carbonyl iron powder, Sendust magnetic powder, Fe-Si-Cr-based metal powder, Fe-based magnetic metal powders such as Fe-Si metal powder, Fe-Ni-based magnetic metal powders such as Permalloy magnetic powder, and Fe-Co-based magnetic metal powders such as Permendur. In other words, as an example of the crystalline material used for the first metal magnetic particles MP1, a crystalline material including at least one alloy selected from the group consisting of FeSi-based alloys, FeSiCr-based alloys, FeSiAl-based alloys, FeCo-based alloys, and FeNi-based alloys can be mentioned. Also, a mixed material (including nanocrystalline materials) may be used. Examples of the nanocrystalline material include Fe-Si-B-Nb-Cu-based nanocrystalline magnetic metal powder. By way of example only, the first metal magnetic particles may use crystalline carbonyl iron powder with 97 wt% or more of Fe. Note that the first metal magnetic particles MP1 are preferably crystalline powders, but amorphous powders described later may also be used.

[0018] The first metal magnetic particles MP1 are coated with a first insulating film IM1. By coating the first metal magnetic particles MP1 with the first insulating film IM1, the first metal magnetic particles MP1 are insulated from each other. As used herein, "insulating property" is intended to mean a volume resistivity of 1 MΩ·cm or more. The first insulating film IM1 may be, for example, an inorganic insulating film formed by a sol-gel reaction of a metal alkoxide. As an example only, it may contain silica as a component.

[0019] -Second Metal Magnetic Particles- As the second magnetic raw material particles, Fe-based metal magnetic particles may be used, for example, an Fe alloy. As an example of the Fe alloy, an alloy containing Fe and Ni, an alloy containing Fe and Co, an alloy containing Fe and Si, an alloy containing Fe, Si and Cr, an alloy containing Fe, Si and Al, an alloy containing Fe, Si, B and Cr, and an alloy containing Fe, P, Cr, Si, B, Nb, Cu and C may be particles of one or more metal magnetic materials selected from the group consisting of. As an example only, an FeSiCrBC-based amorphous alloy or an FeSiCrNbBPCu-based amorphous alloy may be mentioned. More specifically, an amorphous powder of Fe: 93 wt%, Si: 3.5 wt%, B: 3 wt, balance: 0.5 wt% may be used. Note that the second metal magnetic particles MP2 are preferably amorphous powder, but the above-described crystalline powder or mixed system material (including nanocrystalline system materials) may also be used.

[0020] The second metal magnetic particles MP2 are coated with a second insulating film IM2. By coating the second metal magnetic particles MP2 with the second insulating film IM2, the second metal magnetic particles MP2 are insulated from each other. The second insulating film IM2 may be, for example, an inorganic glass film formed by a mechanochemical method. The inorganic glass film may be, for example, a phosphate glass.

[0021] -Resin- Resin R may contain a functional group that contributes to the curing reaction. That is, the curing reaction of resin R may enable the production of the magnetic body 1 by curing. More specifically, resin R at the stage prior to manufacturing the magnetic body 1 is uncured. As used herein, "uncured" refers to the state prior to the state of being almost completely cured, and includes those in a semi-cured state. As an example of resin R, it may be at least one selected from the group consisting of an epoxy resin, a silicone resin, a polyester resin, a polyimide resin, a polyolefin resin, and a phenol resin. Among them, when an epoxy resin is used as resin R, a magnetic body 1 having high electrical insulation and / or mechanical strength can be obtained. As an alternative method, a thermoplastic resin such as polyamideimide, polyphenylene sulfide, and / or liquid crystal polymer may be used. The curing reaction is preferably caused by heat. That is, resin R is preferably a thermosetting resin. As an example, a thermosetting epoxy resin can be mentioned. By using such a resin, the curing reaction can be caused by a simple method.

[0022] The solvent is used to mix the above raw materials (the first metal magnetic particles MP1, the second metal magnetic particles MP2, and resin R) to obtain a slurry, and is preferably an organic solvent. For example, it may contain any of aromatic hydrocarbons such as toluene or xylene; ketones such as acetone, methyl ethyl ketone, or methyl isobutyl ketone; alcohols such as methanol, ethanol, or isopropyl alcohol; glycol ethers such as propylene glycol monomethyl ether or propylene glycol monomethyl ether acetate.

[0023] The curing agent may be used to cure the resin. As an example, it may contain any of an imidazole-based curing agent, an amine-based curing agent, or a guanidine-based curing agent (for example, dicyandiamide).

[0024] The lubricant may be used to improve the lubricity of the first metal magnetic particles MP1 and the second metal magnetic particles MP2 and to improve the filling rate. Further, it may be used to facilitate release from the mold during molding. As the lubricant, for example, any of nanosilica, barium sulfate, or a stearic acid compound (such as lithium stearate, magnesium stearate, zinc stearate, or potassium stearate) may be included.

[0025] In the magnetic body 1 of the present disclosure, when the median particle diameter of the first metal magnetic particles MP1 is D1, the average thickness of the first insulating film IM1 is T1, the median particle diameter of the second metal magnetic particles MP2 is D2, and the average thickness of the second insulating film IM2 is T2, 2.5 ≦ (T1 / D1) / (T2 / D2) ≦ 3.9 T2 ≦ 39.4 nm both are satisfied.

[0026] Hereinafter, the above-described analysis methods of the magnetic body 1 (methods for measuring the median particle diameters D1 and D2 and the average thicknesses T1 and T2) will be described. Note that the "median particle diameter" as used in this specification refers to the particle diameter corresponding to 50% of the cumulative percentage based on volume.

[0027] - Method for measuring median particle diameter - The median particle diameters D1 and D2 of the first metal magnetic particles MP1 and the second metal magnetic particles MP2 of the magnetic body 1 can be obtained by analyzing SEM (scanning electron microscope) images of a cross-section of the magnetic body 1 taken after production.

[0028] First, a cross-section of the magnetic body 1 is cut out with a wire saw or the like and fragmented. After processing the cross-section flat using a milling device or the like, five visual fields each of backscattered electron images at 300 times magnification and 1000 times magnification are acquired by SEM. The reason for acquiring both the 300-fold image (low magnification image) and the 1000-fold image (high magnification image) is to accurately analyze both the particle diameters of the first metal magnetic particles MP1 (small particles) and the second metal magnetic particles MP2 (large particles).

[0029] Next, using image analysis software, perform binarization processing on the acquired SEM images to obtain the equivalent circle diameter of the particle cross-section. Count the frequency of the equivalent circle diameter obtained by image analysis to obtain a histogram. There is a difference in frequency due to the difference in magnification between the 300x image and the 1000x image. In order to align the frequency in the 1000x image with the frequency in the 300x image, multiply the frequency in the 1000x image by the square of (1000 / 300). Furthermore, find the particle size value at which the variation of the histogram of the 1000x image becomes larger than the variation of the histogram of the 300x image. For the frequency of particle sizes larger than this particle size, adopt the value of the 300x image, and for the frequency of particle sizes smaller than this particle size, adopt the value of the 1000x image to obtain one histogram.

[0030] To make the frequency of the histogram the volume-based distribution, based on stereology, perform calculations of multiplying the frequency by the volume calculated from the particle size interval and dividing by the particle size (Reference: "Stereology" by R.T. DeHoff and F.N. Rhines, translated by Kunio Makishima, Yasutada Shinohara, and Naoki Komori, Uchida Rokakuho Publishing Co., Ltd., 1972, pages 167 - 203). The above calculation is based on the study of stereology where particles with smaller cross-sectional areas appear with higher frequencies. Here, normalize by dividing each interval's frequency by the sum of the frequencies so that the sum of the frequencies becomes 1.

[0031] For the volume-based histogram obtained in this way, fit it with the sum of two lognormal distributions (the sum of the lognormal distribution of the first metal magnetic particle MP1 and the lognormal distribution of the second metal magnetic particle MP2) to calculate the median diameter D50 of each of the first metal magnetic particle MP1 and the second metal magnetic particle MP2, as well as the volume ratio (mixing ratio) between the first metal magnetic particle MP1 and the second metal magnetic particle MP2. The probability density function of the lognormal distribution is given by the following formula.

[0032]

Equation

[0033] In the above formula, the variable x corresponds to the data interval, σ corresponds to the variance, and μ corresponds to the mean. Since this probability density function is expressed for each of the first metal magnetic particle MP1 and the second metal magnetic particle MP2, the variables are x1, x2, σ1, σ2, μ1, and μ2, respectively. Note that "1" at the end of each variable means the first metal magnetic particle MP1, and "2" means the second metal magnetic particle MP2. Furthermore, in order to express the probability density function of the first metal magnetic particle MP1 and the probability density function of the second metal magnetic particle MP2 as one probability density function, predetermined ratios (denoted as p1 and p2) are multiplied by the respective probability density functions and then summed. The probability density function obtained in this way, which is the synthesis of the first metal magnetic particle MP1 and the second metal magnetic particle MP2, is normalized so that it can be fitted to the volume-based histogram.

[0034] Among the variables of the probability density function, the data intervals x1 and x2 are given by the data intervals of the volume-based histogram. Therefore, in order to fit the volume-based histogram with the synthesized probability density function, the variances σ1 and σ2, the means μ1 and μ2, and the ratios p1 and p2 are used as variables and optimized by the least squares method so that the difference between the two is minimized. From the probability density functions of the first metal magnetic particle MP1 and the second metal magnetic particle MP2 given by the variables optimized in this way, the normalized density functions are accumulated to obtain the value of the data interval at which it becomes 0.5 (cumulative percentage 50% based on volume), and the median diameters D50 of the first metal magnetic particle MP1 and the second metal magnetic particle MP2 are obtained. Furthermore, from the ratio of the optimized p1 and p2, the volume-based blending ratio (volume ratio) of the first metal magnetic particle MP1 and the second metal magnetic particle MP2 is obtained.

[0035] The above-described analysis method can also be applied when obtaining the volume ratio of the first metal magnetic particle MP1 and the second metal magnetic particle MP2, and the median diameters D50 of the first metal magnetic particle MP1 and the second metal magnetic particle MP2 from the chip cross-section of commercially available products such as inductors.

[0036] -Measurement method of average thickness- The average thickness of the first insulating film IM1 and the average thickness of the second insulating film IM2 can be measured using STEM / EDX (scanning transmission electron microscope / energy-dispersive X-ray analysis). First, the particles to be measured (the first metal magnetic particle MP1 or the second metal magnetic particle MP2) are resin-embedded and polished, and a sample for STEM / EDX observation is prepared by FIB (focused ion beam) processing. By STEM / EDX, an EDX image of the elements contained in the insulating film is obtained at a magnification of 400,000 times. For one particle, three fields of EDX images are taken, and for each EDX image, the thickness of the insulating film is set and measured at four equally spaced points of 30 nm on the surface of the core part. The above measurement is performed for three particles, and the average value calculated from the thicknesses of the insulating films measured at all points (3 fields × 4 points × 3 particles = 36 points) is taken as the average thickness of the insulating film. The thicknesses of the insulating films of the first metal magnetic particle MP1 and the second metal magnetic particle MP2 can also be obtained by performing STEM / EDX analysis in the same procedure as the above method on the cross-section of the molded body composed of the magnetic material. The thickness of the insulating film may be approximately the same value before and after molding.

[0037] When the median particle size of the first metal magnetic particle MP1 is D1, the average thickness of the first insulating film IM1 is T1, the median particle size of the second metal magnetic particle MP2 is D2, and the average thickness of the second insulating film IM2 is T2 by the above measurement method, the magnetic body 1 of the present disclosure satisfies 2.5 ≦ (T1 / D1) / (T2 / D2) ≦ 3.9 and T2 ≦ 39.4 nm. Therefore, while suppressing a decrease in the μ value and improving H sat20 it is possible to improve the filling rate of the magnetic material. The actually measured μ value, H sat20 and the index (fluidity) of the filling rate are described in detail in [Examples].

[0038] -Additional configuration of the magnetic body- As a suitable configuration of the magnetic material, the median particle size D1 of the first metal magnetic particles MP1 may be 4 μm or less. If the median particle size D1 is 4 μm or less, when manufacturing the magnetic material 1, the first metal magnetic particles MP1 flow suitably, so that the filling rate of the first metal magnetic particles MP1 in the magnetic material 1 can be improved. Note that there is no particular limitation on the lower limit of the median particle size D1, but if the median particle size D1 is too small, the specific surface area between the first metal magnetic particles MP1 and the second metal magnetic particles MP2 increases, and the fluidity of the first metal magnetic particles MP1 in the mold K (see FIGS. 4A and 4B) during the manufacture of the magnetic material 1 decreases. Therefore, the lower limit of the median particle size D1 is preferably about 1 μm.

[0039] The median particle size D2 of the second metal magnetic particles MP2 may be 10 μm or more. Although the median particle size D2 may be less than 10 μm, by setting it to 10 μm or more, the specific surface area with the first metal magnetic particles MP1 can be reduced, and the fluidity in the mold K can be improved. Note that there is no particular limitation on the upper limit of the median particle size D2, but if the median particle size D2 is too large, the DC superposition characteristic of the inductor (the characteristic that when the DC current of the inductor is increased, magnetic saturation occurs in the magnetic material and the inductance value decreases) deteriorates. Specifically, the decrease in the inductance value due to magnetic saturation becomes large. Therefore, the upper limit of the median particle size D2 is preferably about 30 μm.

[0040] In the polymerization compounding ratio between the first metal magnetic particles MP1 and the second metal magnetic particles MP2, the weight of the first metal magnetic particles MP1: the weight of the second metal magnetic particles MP2 may be 35:65 or more and 20:80 or less. As an example, the weight of the first metal magnetic particles MP1: the weight of the second metal magnetic particles MP2 may be 25:75. By setting such a polymerization compounding ratio, the first metal magnetic particles MP1 and the second metal magnetic particles MP2 can be made to flow appropriately in the mold K during the manufacture of the magnetic material.

[0041] Regarding the magnetic materials of the first metal magnetic particles MP1 and the second metal magnetic particles MP2, the first metal magnetic particles MP1 may contain Fe, and the second metal magnetic particles MP2 may contain Fe and Si. When the above magnetic materials are adopted, the μ value and H of the manufactured magnetic body sat20 Regarding this, desired inductance characteristics can be obtained.

[0042] As a specific magnetic material of the first metal magnetic particles MP1, the first metal magnetic particles MP1 may contain 97% by weight or more of Fe based on the total amount of the first metal magnetic particles MP1. More specifically, it may be crystalline carbonyl iron powder. By using the above material for the first metal magnetic particles MP1, the μ value and H of the manufactured magnetic body sat20 Regarding this, desired inductance characteristics can be obtained.

[0043] As a specific magnetic material of the second metal magnetic particles MP2, the second metal magnetic particles MP2 may contain 2% by weight or more and 8% by weight or less of Si based on the total amount of the second metal magnetic particles. More specifically, it may be amorphous Fe-Si alloy particles of Fe: 93 wt%, Si: 3.5 wt%, B: 3 wt, and the balance: 0.5 wt%. By using the above material for the second metal magnetic particles MP2, the μ value and H of the manufactured magnetic body sat20 Regarding this, desired inductance characteristics can be obtained.

[0044] The average thickness T1 of the first insulating film IM1 may be 5 nm or more. From the viewpoint of improving the insulation and fluidity between the first metal magnetic particles MP1 (due to the reduction of the frictional force between particles), it is preferable that the average thickness T1 is thicker. However, if the average thickness T1 is 5 nm or more, the insulation and fluidity can be ensured. There is no particular limitation on the upper limit of the average thickness T1. However, if the average thickness T1 is too large, the DC superposition characteristics of the inductor will deteriorate. Specifically, the decrease in the inductance value due to magnetic saturation becomes large. Therefore, it is preferable that the upper limit of the average thickness T1 is about 30 nm.

[0045] As the material of the first insulating film IM1, the first insulating film IM1 may contain silica. More specifically, it may be a silica-containing insulating film formed by a sol-gel reaction of a metal alkoxide (for example, tetraethoxysilane (TEOS)). By using the above material for the first insulating film IM1, an insulating film can be appropriately provided for the first metal magnetic particles MP1 having a relatively small diameter by a sol-gel reaction. Further, the first insulating film IM1 may have an alkyl group imparted to its surface. When an alkyl group is imparted to the surface of the first insulating film IM1, when the first metal magnetic particles MP1 and the second metal magnetic particles MP2 are caused to flow in a mold during the production of the magnetic body, the friction between the particles can be reduced and the fluidity can be improved.

[0046] As described above, the average thickness T2 of the second insulating film IM2 is 39.4 nm or less. If the average thickness T2 is made greater than 39.4 nm, the flow of the second metal magnetic particles MP2 deteriorates when producing the magnetic body 1. Therefore, the upper limit of the average thickness T2 of the second insulating film IM2 was set to 39.4 nm. Note that the average thickness T2 of the second insulating film IM2 is preferably 5 nm or more from the viewpoint of improving insulation. The actually measured fluidity evaluation will be described in detail in [Examples].

[0047] As the material of the second insulating film IM2, the second insulating film IM2 may contain inorganic glass. More specifically, it may be a phosphate glass formed by a mechanochemical method. By using the above material for the second insulating film IM2, an insulating film can be appropriately provided for the second metal magnetic particles MP2 having a relatively large diameter by a mechanochemical method.

[0048] As an embodiment of the resin R used for curing the magnetic body, the resin R may be 2.3% by weight or more and 3.6% by weight or less based on the entire magnetic body. In other words, 96.4% by weight or more and 97.7% by weight or less based on the entire magnetic body corresponds to the magnetic material (the first metal magnetic particles and the second metal magnetic particles). When the magnetic body 1 contains the resin R at the above weight ratio, the magnetic body can be appropriately cured.

[0049] The resin R may be a thermosetting resin. By adopting a thermosetting resin, a curing reaction can be caused by a simple method. When causing the curing reaction, a curing agent (for example, an imidazole-based curing agent) for curing the magnetic body 1 may be used. Also, the curing agent may be added in an amount of about 3 wt% with respect to the main agent (epoxy resin). With such a weight mixing ratio, an appropriate curing reaction can be caused.

[0050] [Method for manufacturing magnetic body] Next, the method for manufacturing the magnetic body 1 described above will be described. The method described below is merely an example, and the method for manufacturing the magnetic body 1 according to the present embodiment is not limited to the following method.

[0051] - Preparation of first metal magnetic particles - First, first metal magnetic particles MP1 having a smaller particle size than the second metal magnetic particles MP2 are prepared. As an example, crystalline carbonyl iron powder (Fe: 97 wt% or more) is prepared. The first metal magnetic particles MP1 are particles having a smaller median particle size compared to the second metal magnetic particles MP2. Therefore, for example, the particle size can be adjusted by air classification in an inert gas environment.

[0052] Next, a first insulating film IM1 is formed on the first metal magnetic particles MP1. The specific procedure is as follows.

[0053] Isopropyl alcohol and aqueous ammonia are mixed and stirred to prepare dispersion liquid 1. Then, a predetermined amount of the crystalline carbonyl iron powder prepared as described above is weighed, isopropyl alcohol is added, and ultrasonic vibration is applied to disperse the carbonyl iron powder to prepare dispersion liquid 2. Dispersion liquid 1 is added to dispersion liquid 2, and the mixture is stirred using a stirrer to obtain dispersion liquid 3.

[0054] Furthermore, tetraethoxysilane (TEOS) is added to isopropyl alcohol and mixed to prepare Surface Treatment Liquid 1. This Surface Treatment Liquid 1 is added to Dispersion Liquid 3 to obtain Reaction Liquid 1, which is stirred by a stirrer to cause a sol-gel reaction, thereby forming a first insulating film IM1 (silica insulating film) on the surface of the carbonyl iron powder. Note that the thickness of the first insulating film IM1 can be controlled, for example, by adjusting the time of the sol-gel reaction, the addition amounts of the metal alkoxide and the solvent, and the like.

[0055] The particles formed with the first insulating film IM1 (silica insulating film) are separated by suction filtration of Reaction Liquid 1 through a membrane filter. The separated particles are appropriately washed with acetone and dried in a natural environment at room temperature. Through the above steps, the dried particles are filtered through a metal mesh to prepare the first metal magnetic particles MP1.

[0056] - Preparation of Second Metal Magnetic Particles - First, second metal magnetic particles MP2 having a larger particle size than the first metal magnetic particles MP1 are prepared. As an example, amorphous powder (Fe: 93 wt%, Si: 3.5 wt%, B: 3 wt, balance: 0.5 wt%) is prepared. The second metal magnetic particles MP2 are particles having a larger median particle size compared to the first metal magnetic particles MP1. Therefore, for example, the particle size can be adjusted by sieving classification.

[0057] Next, a second insulating film IM2 is formed on the second metal magnetic particles MP2. The specific procedure is as follows.

[0058] The second insulating film IM2 is formed by the mechanochemical method. The mechanochemical method is a method that is low-cost and particularly suitable for forming an insulating film with a relatively large thickness on particles having a large particle size. By introducing inorganic glass (for example, phosphate glass) as the material of the insulating film and performing mechanochemical treatment, the second metal magnetic particles MP2 coated with the second insulating film IM2 can be prepared. Note that the film thickness of the second insulating film IM2 can be adjusted by the input amount of phosphate glass during the mechanochemical treatment.

[0059] - Preparation of slurry and supply of slurry to mold - The prepared first metal magnetic particles MP1 and second metal magnetic particles MP2 are mixed with a particle raw material containing a resin R, a solvent, and a curing agent to produce a slurry. Then, the mold K for manufacturing the magnetic body is filled with the slurry.

[0060] Here, the magnetic body 1 according to this embodiment will be described as an E-type core. Note that the shape of the magnetic body is not limited to the E-type core, and may be, for example, at least one selected from the group consisting of an I-type core, a T-type core, a plate-shaped core, and a toroidal ring-shaped core.

[0061] The mold K is filled with the produced slurry S (see Fig. 4A). Then, the mold K is introduced into a compression molding machine and may be pressurized in an environment of 20°C or higher and 40°C or lower, 50 MPa or higher and 150 MPa or lower, and 30 s or less (see Fig. 4B). Here, when the slurry S contains a thermosetting resin as an example, since the temperature during pressurization is relatively low at 20°C or higher and 40°C or lower, the curing reaction may not proceed and it may be in an uncured or semi-cured state. After the pressurization is completed, the magnetic body may be taken out from the mold K.

[0062] In this way, the magnetic body of this embodiment may be stored with the resin in an uncured or semi-cured state. That is, when it is necessary to manufacture a magnetic body that is almost completely cured as a product, the semi-cured magnetic body 1 is filled into a mold different from the mold K, and as the curing conditions for almost completely curing, the resin may be cured in an environment of 150°C or higher and 200°C or lower, 5 MPa or higher and 50 MPa or lower, and 60 s or more and 1800 s or less to manufacture the magnetic body (see Figs. 5A to C). Note that the magnetic body 1 of the present disclosure may be a magnetic body 1 that is completely cured without storing the resin in an uncured or semi-cured state. Further, the magnetic body may be manufactured by forming a sheet containing the slurry S, laminating, pressing, and thermally curing a plurality of sheets.

[0063] By going through the above steps, the magnetic body 1 can be manufactured.

[0064] [About the Inductor] Next, the inductor using the above-described magnetic material will be described. First, the manufacturing method of the inductor will be described with reference to FIGS. 6 and 7. FIG. 6 is a process perspective view schematically showing the manufacturing method of the inductor according to the present embodiment, and FIG. 7 is a perspective view of the inductor according to the present embodiment.

[0065] -Manufacturing Method of Inductor- Prepare a conductive wire 20 to be wound around the magnetic material 1. The conductive wire 20 is preferably composed of a metal wire (for example, a flat copper wire) coated with a resin or the like. In this case, the conductive wire 20 can be firmly molded in combination with the resin contained in the above-described magnetic material 1. The conductive wire 20 is preferably wound by an alpha winding method in which the start and end of winding are simultaneously wound outward. By winding the conductive wire 20 by the alpha winding method, the end of winding is arranged on the outside, so that the handling of the lead-out portion can be easily performed.

[0066] Next, prepare the magnetic material 1 in which the above-described resin is in an uncured or semi-cured state. The alpha-wound conductive wire 20 is accommodated in this magnetic material 1. That is, the magnetic material 1 is arranged at the winding core portion of the coil conductor. At this time, a part of the E-core is inserted into the winding core portion of the conductive wire 20 (see FIG. 6). Further, the above-described slurry S may be further used to coat the conductive wire 20 so as to be hidden by the slurry S. After accommodating these conductive wire 20, magnetic material 1, and slurry S in the above-described mold, they are introduced into a compression molding machine. Then, the resin contained in the magnetic material 1 is cured in an environment of 150°C or higher and 200°C or lower, 5 MPa or higher and 50 MPa or lower, and 60 s or higher and 1800 s or lower to form the inductor body.

[0067] Next, barrel polishing may be performed on the base body, and a process of rounding the edges of the base body may be applied. By rounding the edges, disconnection of the external electrodes formed later can be suppressed. Thereafter, an external electrode 30 is formed on the base body (see FIG. 7). As a method for forming the external electrode 30, a method of forming by plating, a method of applying a conductive paste to the base body and baking it, or a method of forming by sputtering or the like may be used. As an example of the external electrode 30, a thermoset conductive resin paste containing Ag powder, Ni plating, Sn plating, etc. may be mentioned. Further, the external electrode 30 may have a structure in which a plurality of layers thereof are laminated.

[0068] As described above, the inductor 10 using the magnetic body 1 can be manufactured.

Example

[0069] Hereinafter, an experimental test was conducted on the magnetic body of the present disclosure. Specifically, magnetic bodies of Examples 1 to 5 and Comparative Examples 1 to 11 shown below were manufactured.

[0070] The raw materials of the magnetic bodies for Examples 1 to 5 and Comparative Examples 1 to 11 are shown below. First metal magnetic particles: Crystalline carbonyl iron powder Fe: 97 wt% or more First insulating coating: Silica insulating coating Second metal magnetic particles: Fe—Si amorphous alloy Fe: 93 wt%, Si: 3.5 wt%, B: 3 wt%, Others: 0.5 wt% Second insulating coating: Phosphate glass Resin: Thermosetting epoxy resin

[0071] Also, in the magnetic materials of Examples 1 to 5 and Comparative Examples 1 to 11, the median particle size D1 of the first metal magnetic particles, the average thickness T1 of the first insulating film, the median particle size D2 of the second metal magnetic particles, and the average thickness T2 of the second insulating film are as follows. The median particle size D1 of the first metal magnetic particles was adjusted by air classification, and the median particle size D2 of the second metal magnetic particles was adjusted by sieving classification. Also, the average thickness T1 of the first insulating film was adjusted by the TEOS input amount and the sol-gel reaction time, and the average thickness T2 of the second insulating film was adjusted by the input amount of phosphate glass during the mechanochemical treatment.

[0072] <Example 1> The median particle size D1 of the first metal magnetic particles was set to 1.7 μm. The average thickness T1 of the first insulating film was set to 8.0 nm. The median particle size D2 of the second metal magnetic particles was set to 20.5 μm. The average thickness T2 of the second insulating film was set to 39.0 nm.

[0073] <Example 2> The median particle size D1 of the first metal magnetic particles was set to 1.7 μm. The average thickness T1 of the first insulating film was set to 8.0 nm. The median particle size D2 of the second metal magnetic particles was set to 24.8 μm. The average thickness T2 of the second insulating film was set to 39.0 nm.

[0074] <Example 3> The median particle size D1 of the first metal magnetic particles was set to 1.5 μm. The average thickness T1 of the first insulating film was set to 10.0 nm. The median particle size D2 of the second metal magnetic particles was set to 21.7 μm. The average thickness T2 of the second insulating film was set to 39.4 nm.

[0075] <Example 4> The median particle size D1 of the first metal magnetic particles was set to 1.5 μm. The average thickness T1 of the first insulating film was set to 10.0 nm. The median particle size D2 of the second metal magnetic particles was set to 22.0 μm. The average thickness T2 of the second insulating film was set to 37.8 nm.

[0076] <Example 5> The median particle size D1 of the first metal magnetic particles was set to 1.5 μm. The average thickness T1 of the first insulating film was set to 10.0 nm. The median particle size D2 of the second metal magnetic particles was set to 21.6 μm. The average thickness T2 of the second insulating film was set to 37.1 nm.

[0077] <Comparative Example 1> The median particle size D1 of the first metal magnetic particles was set to 1.5 μm. The average thickness T1 of the first insulating film was set to 10.0 nm. The median particle size D2 of the second metal magnetic particles was set to 27.8 μm. The average thickness T2 of the second insulating film was set to 39.0 nm.

[0078] <Comparative Example 2> The median particle size D1 of the first metal magnetic particles was set to 1.3 μm. The average thickness T1 of the first insulating film was set to 10.0 nm. The median particle size D2 of the second metal magnetic particles was set to 27.8 μm. The average thickness T2 of the second insulating film was set to 39.0 nm.

[0079] <Comparative Example 3> The median particle size D1 of the first metal magnetic particles was set to 1.5 μm. The average thickness T1 of the first insulating film was set to 10.0 nm. The median particle size D2 of the second metal magnetic particles was set to 27.8 μm. The average thickness T2 of the second insulating film was set to 22.9 nm.

[0080] <Comparative Example 4> The median particle size D1 of the first metal magnetic particles was set to 1.5 μm. The average thickness T1 of the first insulating film was set to 10.0 nm. The median particle size D2 of the second metal magnetic particles was set to 21.6 μm. The average thickness T2 of the second insulating film was set to 12.5 nm.

[0081] <Comparative Example 5> The median particle size D1 of the first metal magnetic particles was set to 1.5 μm. The average thickness T1 of the first insulating film was set to 10.0 nm. The median particle size D2 of the second metal magnetic particles was set to 27.8 μm. The average thickness T2 of the second insulating film was set to 12.9 nm.

[0082] <Comparative Example 6> The median particle size D1 of the first metal magnetic particles was set to 1.3 μm. The average thickness T1 of the first insulating film was set to 10.0 nm. The median particle size D2 of the second metal magnetic particles was set to 27.8 μm. The average thickness T2 of the second insulating film was set to 12.9 nm.

[0083] <Comparative Example 7> The median particle size D1 of the first metal magnetic particles was set to 1.5 μm. The average thickness T1 of the first insulating film was set to 10.0 nm. The median particle size D2 of the second metal magnetic particles was set to 22.0 μm. The average thickness T2 of the second insulating film was set to 55.0 nm.

[0084] <Comparative Example 8> The median particle size D1 of the first metal magnetic particles was set to 1.5 μm. The average thickness T1 of the first insulating film was set to 10.0 nm. The median particle size D2 of the second metal magnetic particles was set to 22.0 μm. The average thickness T2 of the second insulating film was set to 80.0 nm.

[0085] <Comparative Example 9> The median particle size D1 of the first metal magnetic particles was set to 1.5 μm. The average thickness T1 of the first insulating film was set to 10.0 nm. The median particle size D2 of the second metal magnetic particles was set to 22.0 μm. The average thickness T2 of the second insulating film was set to 100.0 nm.

[0086] <Comparative Example 10> The median particle size D1 of the first metal magnetic particles was set to 2.5 μm. The average thickness T1 of the first insulating film was set to 8.0 nm. The median particle size D2 of the second metal magnetic particles was 12.0 μm. The average thickness T2 of the second insulating film was set to 39.0 nm.

[0087] <Comparative Example 11> The median particle size D1 of the first metal magnetic particles was set to 1.7 μm. The average thickness T1 of the first insulating film was set to 8.0 nm. The median particle size D2 of the second metal magnetic particles was set to 14.9 μm. The average thickness T2 of the second insulating film was set to 39.0 nm.

[0088] The method for manufacturing the magnetic body is as described in the above [Method for manufacturing magnetic body]. The magnetic body was in the form of a toroidal ring.

[0089] Regarding the magnetic bodies of the above Examples 1 to 5 and Comparative Examples 1 to 11, the following evaluations were made for [Inductance characteristic evaluation] and [Evaluation of fluidity of slurry during magnetic body production].

[0090] [Inductance characteristic evaluation] As the inductance characteristics, the relative permeability μ' and H sat20 were measured with an impedance analyzer, and μ'×H sat20 was calculated, and the inductance characteristics of the magnetic body were evaluated using the calculated value.

[0091] The evaluation of the relative permeability μ' was performed using an impedance analyzer (E4991A manufactured by Keysight). In the relative permeability measurement, the value at 1 MHz was adopted. Note that a larger value of the relative permeability μ' indicates better inductance characteristics.

[0092] H sat20 The evaluation of H was carried out using an LCR meter (4284A manufactured by Keysight). First, the magnetic materials of Examples 1 to 5 and Comparative Examples 1 to 11 were wound with a copper wire. A copper wire with a diameter of 0.35 mm was used, and the number of turns was 24. A DC current of 0 to 30 A was applied to the copper wire to obtain the inductance (L value). The relative permeability (μ value) was calculated from the L value, and the current value (I sat20 ) was obtained when the μ value decreased from the μ value at zero current to 80% of the μ value. From I sat20 , the magnetic field (H sat20 ) at which the μ value becomes 80% was calculated based on the dimensions of the ring and the number of turns of the copper wire. Note that the larger the value of H sat20 , the better the DC superposition characteristics.

[0093] [Evaluation of the fluidity of the slurry during the manufacture of the magnetic material] The evaluation of the fluidity of the slurry was to evaluate the ease of flow of the slurry in the mold when the slurry was introduced into the mold in the process of manufacturing the magnetic material. If the fluidity is small, poor filling of the slurry in the mold occurs during the molding of the magnetic material, so a larger fluidity is preferred.

[0094] Specifically, for the evaluation of the fluidity, a flow tester (CFT500EX manufactured by Shimadzu Corporation) was used, with a measurement die: φ3 mm × 1 mm thick, a charged amount of 5 g, a cylinder temperature of 130 °C, a preheating time of 60 s, and a test force of 20 MPa. The average value at a flow rate of 3 mm to 5 mm was measured.

[0095] [Evaluation results] The results of the [inductance characteristic evaluation] and the [evaluation of the fluidity of the slurry during the manufacture of the magnetic material] for Examples 1 to 5 and Comparative Examples 1 to 11 are shown in FIG. 8. Note that the evaluation criteria for μ'×H sat20 were that a value of 450 kA / m or more was considered qualified and a value less than 450 kA / m was considered unqualified. The evaluation criteria for the relative permeability μ' were that a value of 24.5 or more was considered qualified and a value less than 24.5 was considered unqualified. The evaluation criteria for the fluidity were that a value of 0.25 cc / s or more was considered qualified and a value less than 0.25 cc / s was considered unqualified.

[0096] For the magnetic materials of Examples 1 to 5, good results were obtained in both [Inductance Characteristic Evaluation] and [Slurry Fluidity Evaluation during Magnetic Material Production]. On the other hand, the magnetic materials of Comparative Examples 1 to 11 did not meet the above evaluation criteria for either one or both of [Inductance Characteristic Evaluation] and [Slurry Fluidity Evaluation during Magnetic Material Production].

[0097] Note that the embodiments disclosed this time are illustrative in all respects and are not a basis for restrictive interpretation. Therefore, the technical scope of the present disclosure is not interpreted only by the above-described embodiments, but is defined based on the description of the claims. Also, the technical scope of the present disclosure includes all modifications within the meaning and scope equivalent to the claims.

[0098] Aspects of the coil component of the present disclosure are as follows. <1> including first metal magnetic particles, second metal magnetic particles having a median particle size larger than that of the first metal magnetic particles, and a resin, the first metal magnetic particles are coated with a first insulating film, the second metal magnetic particles are coated with a second insulating film, when the median particle size of the first metal magnetic particles is D1, the average thickness of the first insulating film is T1, the median particle size of the second metal magnetic particles is D2, and the average thickness of the second insulating film is T2, 2.5 ≤ (T1 / D1) / (T2 / D2) ≤ 3.9 T2 ≤ 39.4 nm a magnetic material that satisfies both. <2> The magnetic material according to <1>, wherein the median particle size D1 of the first metal magnetic particles is 4 μm or less. <3> The magnetic material according to <1> or <2>, wherein the median particle size D2 of the second metal magnetic particles is 10 μm or more. <4> The magnetic material according to any one of <1> to <3>, wherein the average thickness T1 of the first insulating film is 5 nm or more. <5> The weight mixing ratio of the first metal magnetic particles and the second metal magnetic particles is The weight of the first metal magnetic particles: the weight of the second metal magnetic particles is 35:65 or more and 20:80 or less, and the magnetic material according to any one of <1> to <4>. <6>The resin is 2.3% by weight or more and 3.6% by weight or less based on the entire magnetic material, and the magnetic material according to any one of <1> to <5>. <7>The first metal magnetic particles contain Fe, and the second metal magnetic particles contain Fe and Si, and the magnetic material according to any one of <1> to <6>. <8>The first metal magnetic particles contain 97% by weight or more of crystalline Fe based on the entire first metal magnetic particles, and the magnetic material according to <7>. <9>The second metal magnetic particles contain 2% by weight or more and 8% by weight or less of Si based on the entire second metal magnetic particles, and the magnetic material according to <7> or <8>. <10>The first insulating film contains silica, and the magnetic material according to any one of <1> to <9>. <11>The second insulating film contains inorganic glass, and the magnetic material according to any one of <1> to <10>. <12>The resin is a thermosetting resin, and the magnetic material according to any one of <1> to <11>. <13>An inductor including the magnetic material according to any one of <1> to <12>.

Industrial Applicability

[0099] The magnetic material and inductor of the present disclosure can be suitably used as electronic components that suppress a decrease in the μ value and improve H sat20 and can be suitably used.

Explanation of Signs

[0100] 1 Magnetic material 10 Inductor 20 Conductive wire 30 External electrode MP1 First metal magnetic particles MP2 Second metal magnetic particles IM1 First insulating film IM2 Second insulating film K mold S slurry

Claims

1. A magnetic material comprising first metal magnetic particles, second metal magnetic particles having a median particle size larger than that of the first metal magnetic particles, and a resin, wherein the first metal magnetic particles are coated with a first insulating film, the second metal magnetic particles are coated with a second insulating film, when the median particle size of the first metal magnetic particles is D1, the average thickness of the first insulating film is T1, the median particle size of the second metal magnetic particles is D2, and the average thickness of the second insulating film is T2, 2.5 ≤ (T1 / D1) / (T2 / D2) ≤ 3.9 T2 ≤ 39.4 nm and both of which are satisfied.

2. The magnetic material according to claim 1, wherein the median particle size D1 of the first metal magnetic particles is 4 μm or less.

3. The magnetic material according to claim 1, wherein the median particle size D2 of the second metal magnetic particles is 10 μm or more.

4. The magnetic material according to claim 1, wherein the average thickness T1 of the first insulating film is 5 nm or more.

5. The weight mixing ratio of the first metal magnetic particles to the second metal magnetic particles is the weight of the first metal magnetic particles: the weight of the second metal magnetic particles is 35:65 or more and 20:80 or less. The magnetic material according to claim 1.

6. The magnetic material according to claim 1, wherein the resin is 2.3% by weight or more and 3.6% by weight or less based on the entire magnetic material.

7. The magnetic material according to claim 1, wherein the first metal magnetic particles contain Fe, and the second metal magnetic particles contain Fe and Si.

8. The magnetic material according to claim 7, wherein the first metal magnetic particles contain 97% by weight or more of crystalline Fe based on the entire first metal magnetic particles.

9. The magnetic material according to claim 7, wherein the second metal magnetic particles contain 2% by weight or more and 8% by weight or less of Si based on the entire second metal magnetic particles.

10. The magnetic material according to claim 1, wherein the first insulating film contains silica.

11. The magnetic material according to claim 1, wherein the second insulating film contains inorganic glass.

12. The magnetic material according to claim 1, wherein the resin is a thermosetting resin.

13. An inductor comprising the magnetic material according to any one of claims 1 to 12.

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