Powder magnetic core and electronic component

Abstract

A dust core contains magnetic particles, an epoxy resin, and an additive. The epoxy resin has at least two or more mesogenic skeletons between two epoxy bonds close to each other along a molecular chain. The additive contains one or more metal elements selected from Li, Ba, Mg, and Ca.

Description

TECHNICAL FIELD

[0001] The present application relates to a powder magnetic core and an electronic component provided with the powder magnetic core. BACKGROUND

[0002] A powder magnetic core for a magnetic electronic component such as an inductor or a reactor is generally manufactured by mixing and compression-molding magnetic particles together with a binder (binding material). It is known that, in the powder magnetic core, an additive material such as a lubricant or a corrosion preventive, a dispersant, or the like is used in order to improve characteristics such as moldability or corrosion resistance. For example, in Patent Documents 1 and 2, a powder magnetic core to which a metal soap powder is added as a lubricant is disclosed.

[0003] However, the additive material described above is a non-magnetic material. Therefore, if the additive material described above is added to the powder magnetic core, improvement in moldability or corrosion resistance can be expected, but on the contrary, magnetic characteristics such as permeability sometimes deteriorate. That is, the improvement effect in moldability or corrosion resistance by the additive material and the magnetic characteristics of the powder magnetic core are in opposite relationship, and in particular, it is difficult to achieve both high permeability and high rust resistance.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT DOCUMENTS

[0006] Patent Document 1: Japanese Patent Application Publication No. 2011-199049

[0007] Patent Document 2: Japanese Patent Application Publication No. 2014-086672 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] The present application was developed in view of the above-described circumstances, and aims to provide a powder magnetic core that has both high permeability and high rust resistance, and an electronic component using the powder magnetic core.

[0011] TECHNICAL SOLUTION TO THE PROBLEM

[0012] In order to achieve the above-described object, the present application provides a powder magnetic core that contains magnetic particles, an epoxy resin, and an additive material,

[0013] The epoxy resin described above has at least two or more mesogenic skeletons between two epoxy bonds that are close along a molecular chain,

[0014] The additive material described above contains a metal element M selected from one or more of Li, Ba, Mg, and Ca.

[0015] Through in-depth research, the inventors discovered a special correlation between the amount of mesocrystalline skeleton in epoxy resin and the characteristics of the additives, leading to the completion of this invention.

[0016] Specifically, according to the inventors' experiments, when using a resin with 0 or 1 mesocrystalline framework between epoxy bonds as a binder, even adding an additive containing the aforementioned metal element M (selected from at least one of Li, Ba, Mg, and Ca) to the powder-pressed magnetic core cannot effectively improve rust resistance. Furthermore, in this case, even if increasing the content of the additive improves rust resistance, the magnetic permeability decreases, making it impossible to simultaneously achieve high rust resistance and high magnetic permeability. On the other hand, when using an epoxy resin with 2 or more mesocrystalline framework between epoxy bonds as a binder, adding an additive containing the metal element M to the powder-pressed magnetic core can achieve both high magnetic permeability and high rust resistance.

[0017] When the above-mentioned additives contain Li, it is preferable that the weight ratio of Li relative to the total weight of the magnetic particles, the epoxy resin and the above-mentioned additives is more than 10 ppm and less than 100 ppm.

[0018] When the above-mentioned additives contain Ba, it is preferable that the weight ratio of Ba relative to the total weight of the above-mentioned magnetic particles, the above-mentioned epoxy resin and the above-mentioned additives is more than 190 ppm and less than 600 ppm.

[0019] When the above-mentioned additives contain Mg, it is preferable that the weight ratio of Mg to the total weight of the magnetic particles, the epoxy resin and the above-mentioned additives is 30 ppm to 130 ppm.

[0020] When the above-mentioned additives contain Ca, it is preferable that the weight ratio of Ca relative to the total weight of the magnetic particles, the epoxy resin and the above-mentioned additives is 60 ppm to 200 ppm.

[0021] As mentioned above, by controlling the content of metal element M in the pressed powder core within a specified range, it is possible to simultaneously achieve higher magnetic permeability and higher rust resistance.

[0022] Preferably, the magnetic particles are metal particles with Fe as the main component.

[0023] The pressed powder magnetic core of the present invention can be applied to various electronic components such as inductors, reactors, transformers, non-contact power supply coils, and magnetic shielding parts, and is particularly preferred as a magnetic core for inductors. Attached Figure Description

[0024] Figure 1is a schematic sectional view of an inductor element of one embodiment of the present application.

[0025] Figure 2 is an enlarged view of a portion of the powder magnetic core shown in Figure 1

[0026] Figure 3 is a graph summarizing the evaluation results of the examples shown in Tables 3 to 11.

[0027] Explanation of Reference Numerals

[0028] 100 inductor element, 110 powder magnetic core, 2 binder, 4 magnetic particles, 4a large particles, 4b small particles, 120 coil DETAILED DESCRIPTION

[0029] Hereinafter, the present application will be described in detail based on the embodiments shown in the drawings.

[0030] As shown in Figure 1 , an inductor element 100 of one embodiment of the present application has a powder magnetic core 110 and a coil 120 embedded inside the powder magnetic core 110.

[0031] The shape of the powder magnetic core 110 is not particularly limited, and can be set to, for example, a cylindrical shape, an elliptical cylindrical shape, a prismatic shape, or the like. Also, as shown in Figure 2 , the powder magnetic core 110 contains a binder 2 as a binding material, magnetic particles 4 dispersed in the binder 2, and a prescribed additive material 6 (not shown), and can further contain non-magnetic inorganic particles or the like. That is, the powder magnetic core 110 is formed into a prescribed shape by a plurality of magnetic particles 4 being bound via the binder 2. Hereinafter, the binder 2, the magnetic particles 4, and the additive material 6 that constitute the powder magnetic core 110 will be described in detail.

[0032] The binder 2 is mainly composed of a cured epoxy resin and a phenol resin, and can further contain a trace amount of an organic component. Here, the "trace amount of an organic component" refers to components resulting from a lubricant, a curing accelerator, a softener, a plasticizer, a dispersant, a colorant, an anti-settling agent, or the like, and can be contained in an amount of 1.0 parts by mass or less with respect to 100 parts by mass of the main component of the binder 2, i.e., the epoxy resin.

[0033] In the present embodiment, it is characterized in that the epoxy resin of the binder 2 has a prescribed molecular structure. Specifically, the epoxy resin of the binder 2 has a plurality of mesogenic skeletons between two epoxy bonds close to each other along the molecular chain.

[0034] ​In this embodiment, the "epoxy bond" refers to the molecular arrangement formed by ring opening of the epoxy group present in the prepolymer by polymerization (curing reaction). In addition, the "mesogen skeleton" is a general term for an atomic group containing a polycyclic aromatic hydrocarbon or two or more aromatic rings, and having rigidity and orientability.

[0035] More specifically, the mesogen skeleton is preferably a partial structure represented by the following (J) formula.

[0036]

[0037] In the above (J) formula, X is a single bond or at least one linking group selected from the group (A) described below.

[0038]

[0039] In addition, in the above (J) formula, Y is selected from -H (hydrogen), alkyl (aliphatic hydrocarbon having 4 or less carbon atoms), acetyl group, and halogen, and Y in the mesogen skeleton can be the same or different. Also, * in the (J) formula indicates the bonding site with the adjacent atom.

[0040] In particular, in this embodiment, the mesogen skeleton is more preferably a partial structure represented by the following (I) formula.

[0041]

[0042] Y and * in the above (I) formula are the same as in the (J) formula. That is, in the mesogen skeleton represented by the (I) formula, X in the (J) formula is set to a single bond, and compared to the (J) formula, the number of Y capable of disposing a functional group (side chain of alkyl, acetyl group, halogen, etc.) is limited.

[0043] It is considered that the above mesogen skeleton exhibits the effect of improving the lubricity between the magnetic particles 4 during molding and efficiently promoting the rearrangement of the magnetic particles 4. In addition, it is also considered that stacking (molecular overlap) is easily formed between the mesogen skeletons after curing, and this stacking contributes to the improvement of the mechanical strength of the binder 2 and the powder magnetic core 110. Furthermore, it is also considered that the mesogen skeleton also exhibits the effect of reducing the thermal resistance between the magnetic particles 4. Therefore, by forming the powder magnetic core 110 from the epoxy resin containing the mesogen skeleton, it is expected that the density, strength, relative permeability, thermal conductivity, etc. are improved. Furthermore, the above "rearrangement of the magnetic particles 4" refers to the movement of the particles by pressure to approach the closest packing state.

[0044] In the epoxy resin of the adhesive 2 of the present embodiment, there are at least two or more (preferably 10 or less, more preferably 3 or less) of the above mesogenic skeletons between two epoxy bonds close to each other along the molecular chain. The upper limit of the number of the mesogenic skeletons present between the epoxy bonds is not particularly limited, and can be, for example, 100 or less. Furthermore, the plurality of mesogenic skeletons present between the close epoxy bonds can be different from each other, or can be the same structure. In addition, the plurality of mesogenic skeletons between the two close epoxy bonds can be present continuously by being linked by a single bond, or can be linked via a single or a plurality of linking groups.

[0045] Here, the "two epoxy bonds close to each other" is described in more detail. The molecular structure having the plurality of mesogenic skeletons described above can be achieved, for example, by curing an epoxy resin having a prepolymer represented by the following (K) formula.

[0046]

[0047] In the prepolymer represented by the formula (K), both E1 and E2 at the terminal are epoxy groups. In addition, M1 and M3 in the formula (K) are mesogenic skeletons. If the epoxy resin having the prepolymer of the formula (K) is cured, the epoxy groups of E1 and E2 are ring-opened to form a high molecular chain. In this case, between the ring-opened E1 and E2, "between two epoxy bonds close to each other along the molecular chain" corresponds, and "1 (M1) + n (M3)" mesogenic skeletons are present between the epoxy bonds.

[0048] Furthermore, the number of the mesogenic skeletons present between the epoxy bonds can be specified by analyzing the molecular structure of the adhesive 2. For example, it is sufficient to appropriately use nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FT-IR), gas chromatography-mass spectrometry (GC / MS), liquid chromatography-mass spectrometry (LC / MS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and the like to analyze the molecular structure of the adhesive 2. In addition, the sample for measurement can be prepared by collecting the adhesive 2 from the powder magnetic core 110 represented by the formula (A). Figure 1 The sample for measurement can be prepared by collecting the adhesive 2 from the powder magnetic core 110 represented by the formula (A).

[0049] In the present embodiment, the magnetic particles 4 can be soft magnetic particles. The soft magnetic particles can be oxide magnetic particles such as soft ferrite, but are preferably soft magnetic metal particles containing Fe as a main component. Here, "containing Fe as a main component" means that the content of Fe contained in the soft magnetic metal particles per unit mass is 60 wt% or more. As such soft magnetic metal particles, for example, pure iron, Fe-Si-based alloys (iron-silicon), Fe-Al-based alloys (iron-aluminum), permalloy-based alloys (Fe-Ni), iron-silicon-aluminum-based alloys (Fe-Si-Al), Fe-Si-Cr-based alloys (iron-silicon-chromium), Fe-Si-Al-Ni-based alloys, Fe-Ni-Si-Co-based alloys, Fe-based amorphous alloys, Fe-based nanocrystalline alloys, and the like can be exemplified.

[0050] Further, it is preferable that the magnetic particles 4 as the soft magnetic metal particles do not substantially contain the metal elements M such as Li, Ba, Mg, Ca, and the like contained in the additive material 6. "Do not substantially contain" means that the content of the metal elements M contained in the soft magnetic metal particles per unit mass is less than 100 ppm.

[0051] In addition, it is preferable that an insulating coating is formed on the surface of the soft magnetic metal particles as the magnetic particles 4. As the insulating coating, for example, a coating film (oxide film) formed by particle surface oxidation, a phosphate coating film, a silicate coating film, a glass coating, an inorganic coating film containing BN, SiO2, MgO, Al2O3, or the like, or an organic coating film, and the like can be exemplified. These insulating coatings can be formed by surface treatment such as heat treatment, phosphate treatment, mechanical alloying treatment, silane coupling treatment, hydrothermal synthesis, or the like. By forming the insulating coating on the metal magnetic particles, it is possible to suppress the high frequency loss of the powder magnetic core 110.

[0052] The average particle diameter (D50) of the magnetic particles 4 is not particularly limited, and for example, can be 50 μm or less, and is preferably in the range of 20 μm to 40 μm. Further, the average particle diameter of the magnetic particles 4 can be measured by performing image analysis on the cross section of the powder magnetic core 110 shown in FIG. 1. Figure 2 Specifically, by measuring the area of each particle contained in the cross section shown in FIG. 1, and calculating the equivalent circle diameter of each particle from the area value, the particle size distribution of the magnetic particles 4 can be obtained. In this measurement, the size of the field of view can be appropriately adjusted according to the particle size of the magnetic particles 4 observed, and it is preferable to perform analysis on at least 5 fields of view or more to obtain the particle size distribution. Figure 2

[0053] Further, the magnetic particles 4 contained in the powder magnetic core 110 can be composed of the same material throughout, or can be composed of a plurality of particles having different materials. In addition, as shown in FIG. 2, the powder magnetic core 110 can be composed of a plurality of magnetic particles 4 having different particle sizes. Figure 2 ​As shown, the magnetic particles 4 can also be composed of a plurality of particles having different particle sizes. For example, the magnetic particles 4 can be composed of large particles 4a composed of a Fe-Si alloy and small particles 4b composed of pure iron having an average particle size smaller than that of the large particles 4a.

[0054] In addition, in the case where the magnetic particles 4 are soft magnetic metal particles, the content of the binder 2 in the powder magnetic core 110 is preferably 4.0 parts by mass or less, and more preferably 1.0 part by mass to 4.0 parts by mass, with respect to 100 parts by mass of the magnetic particles 4. In the powder magnetic core 110 of the present embodiment, by using an epoxy resin having a plurality of mesogenic skeletons between the epoxy bonds, even if the proportion of the binder 2 with respect to the magnetic particles 4 is reduced, the shape retention can be ensured, and a high strength can be obtained.

[0055] Further, the content of the binder can be estimated by analyzing the powder magnetic core using an inductively coupled plasma atomic emission spectrometer (ICP-AES). At this time, the powder magnetic core is dissolved using, for example, hydrochloric acid, and a sample for analysis is prepared, and the content of the binder is calculated by estimating the intensity of the elements detected by the ICP-AES.

[0056] The additive material 6 is an organometallic compound containing one or more metal elements M selected from Li, Ba, Mg, and Ca. In this regard, as the organometallic compound, for example, metal alkoxides, metal complexes, fatty acid salts, and the like can be given, and a fatty acid salt is preferable. In the case where the additive material 6 is a fatty acid salt, as the fatty acid constituting the additive material 6, for example, stearic acid, montanic acid, lauric acid, myristic acid, ricinoleic acid, behenic acid, palmitic acid, 12-hydroxystearic acid, and the like can be given, and stearic acid, montanic acid, and lauric acid are more preferable.

[0057] The state of existence of the additive material 6 in the powder magnetic core 110 is not particularly limited, and the additive material 6 can be dispersed in the binder 2 or can be attached to the surface of the magnetic particles. The additive material 6 functions as a lubricant during the manufacturing process of the powder magnetic core 110, and suppresses molding defects. In addition, by containing the additive material 6 having the metal element M in the powder magnetic core 110, it is possible to suppress a decrease in permeability while achieving an improvement in rust resistance.

[0058] In addition, by controlling the content of the metal element M in the powder magnetic core 110 within a prescribed range, a higher permeability and a higher corrosion resistance are obtained. Specifically, in the case where the additive material 6 contains Li, the weight ratio R of Li with respect to the total weight (100 wt%) of the binder 2 (epoxy resin), the magnetic particles 4, and the additive material 6 is preferably 0.0001 wt% or more and 0.1 wt% or less. Li It can be set within a range of 2 ppm to 500 ppm, and is preferably 10 ppm or more and 100 ppm or less.

[0059] In the case where the additive material 6 contains Ba, the weight ratio R of Ba with respect to the total weight of the binder 2, the magnetic particles 4, and the additive material 6 Ba It is possible to be in the range of 15 ppm to 4000 ppm, preferably 100 ppm or more and 2000 ppm or less, more preferably 190 ppm or more and 600 ppm or less.

[0060] In the case where the additive material 6 contains Mg, the weight ratio R of Mg with respect to the total weight of the binder 2, the magnetic particles 4, and the additive material 6 Mg It is possible to be in the range of 4 ppm to 900 ppm, preferably 30 ppm or more and 400 ppm or less, more preferably 30 ppm or more and 130 ppm or less, further preferably 40 ppm or more.

[0061] In addition, in the case where the additive material 6 contains Ca, the weight ratio R of Ca with respect to the total weight of the binder 2, the magnetic particles 4, and the additive material 6 Ca It is possible to be in the range of 5 ppm to 1400 ppm, preferably 50 ppm or more and 700 ppm or less, more preferably 60 ppm or more and 200 ppm or less.

[0062] The main constituent elements of the powder magnetic core 110 are the above-described binder 2, the magnetic particles 4, and the additive material 6, and in the case where other elements such as non-magnetic ceramic particles are not contained, the weight ratio R of the above-described metal element M M (R Li , R Ba , R Mg , R Ca ) corresponds to the content rate of the metal element M contained in the powder magnetic core 110 per unit mass. Furthermore, the weight ratio R of the metal element M M It is possible to measure by inductively coupled plasma emission spectrometry (ICP) after dissolving the powder magnetic core 110 with hydrochloric acid or the like to obtain a measurement sample.

[0063] In addition, the above-described weight ratio R of the metal element M M based on the mass of the metal element M contained in the powder magnetic core 110 due to the additive material 6. In the present embodiment, the constituent elements other than the additive material 6 such as the magnetic particles 4 do not substantially contain the metal element M, and the weight ratio R is calculated based on the mass of the metal element M contained in the measurement sample collected from the powder magnetic core 110 M It is possible to measure by inductively coupled plasma emission spectrometry (ICP) after dissolving the powder magnetic core 110 with hydrochloric acid or the like to obtain a measurement sample. M It is possible to measure by inductively coupled plasma emission spectrometry (ICP) after dissolving the powder magnetic core 110 with hydrochloric acid or the like to obtain a measurement sample.

[0064] Further, two or more kinds of metal elements M can be contained in the powder magnetic core 110. That is, a plurality of additive materials 6 can be contained, for example, lithium stearate and magnesium stearate can be added in combination as the additive material 6.

[0065] Further, it is preferable that the powder magnetic core 110 substantially does not contain other organic metal compounds that do not contain the metal element M, and it is particularly preferable that the powder magnetic core 110 substantially does not contain an organic metal compound containing Zn. That is, the content of Zn contained in the powder magnetic core 110 per unit mass is preferably 50 ppm or less. By setting the content of the organic metal compound having Zn as a constituent element within the above range, a decrease in permeability can be suppressed.

[0066] Next, a manufacturing method of the inductor element 100 shown in FIG. 1 will be described. Figure 1

[0067] First, a resin material as a raw material of the binder 2, a raw powder of the magnetic particle 4, and the additive material 6 are prepared. The raw powder of the magnetic particle 4 can be produced by a publicly known powder production method. As the powder production method, for example, a gas atomization method, a water atomization method, a spinning disk method, a carbonyl method, and the like can be given. Alternatively, a thin ribbon obtained by a single roll method can be mechanically pulverized to produce the raw powder. Further, after the raw powder of the magnetic particle 4 is obtained by the above production method, the particle size of the magnetic particle 4 can be controlled by performing sieve classification or air flow classification, or the like. In addition, in a case where an insulating coating is formed on the surface of the magnetic particle 4, a heat treatment or a surface treatment such as a phosphate treatment, a mechanical alloying treatment, a silane coupling treatment, a hydrothermal synthesis, or the like can be performed on the obtained raw powder.

[0068] As the resin raw material of the binder 2, an epoxy resin composed of a prepolymer before curing is prepared. The epoxy resin has at least two or more mesogenic skeletons between two epoxy groups at the end of the prepolymer.

[0069] Further, a paint is produced by dissolving the above epoxy resin and a phenol resin as a curing agent in a solvent. At this time, it is preferable to use a curing agent having a molecular weight of about 500 to 10,000. In addition, the solvent is not particularly limited, and acetone, isopropyl alcohol (IPA), methyl ethyl ketone (MEK), butyl diglycol acetate (BCA), methanol, or the like can be used. Further, a curing accelerator (curing catalyst), a flexibilizer, a plasticizer, a dispersant, a colorant, an anti-settling agent, or the like can be appropriately added to the above paint. In addition, the amount of the curing agent to be added is appropriately determined in accordance with the amount of the epoxy resin to be blended.

[0070] ​A powder containing an organometallic compound of metal element M is prepared as additive material 6. The average particle size (D50) of the organometallic compound powder is preferably about 2 μm to 15 μm, and is preferably smaller than the average particle size of the raw material powder of magnetic particles 4.

[0071] Next, the precursor for pressed magnetic cores is prepared by mixing the raw material powder of magnetic particles 4, the coating containing epoxy resin, and the additive 6 in various mixing machines such as kneaders or twin-screw extruders. At this time, it is preferable to combine the raw material powder and coating with the binder 2 in a ratio of 1 to 4 parts by weight relative to 100 parts by weight of magnetic particles. Furthermore, it is preferable to control the proportion of the additive 6 so that the weight ratio R of the metal element M in the pressed magnetic core 110 is... M Within the aforementioned scope. Furthermore, material 6 may also be added to the raw material powder of the magnetic particles 4 and mixed before this mixing process. Additionally, depending on the application of the inductor element, non-magnetic ceramic particles, etc., may be appropriately added during this mixing process.

[0072] Next, the aforementioned precursor is used to manufacture the powder-pressed magnetic core. Figure 1 In the case of the inductor element 100 shown, the precursor and the hollow coil, which serves as an insert component, are filled into a mold and compressed. This yields a molded body having the shape of the powder-coated magnetic core to be manufactured. The epoxy resin in the molded body is then cured by appropriately subjecting it to heat treatment. There are no particular restrictions on the heat treatment conditions, as long as the epoxy resin is sufficiently cured. For example, the heat treatment temperature can be set to 150°C to 200°C, and the treatment time to 1 hour to 5 hours. There are no particular restrictions on the atmosphere during heat treatment; an atmospheric atmosphere can also be used.

[0073] Through the above process, an inductor element 100 with a coil 120 embedded inside the pressed powder magnetic core 110 can be obtained.

[0074] (Summary of this implementation method)

[0075] The pressed powder magnetic core 110 of this embodiment includes a binder 2 containing epoxy resin and phenolic resin, magnetic particles 4 dispersed in the binder 2, and additive material 6. The epoxy resin contained in the binder 2 has at least two or more mesocrystalline frameworks between two epoxy bonds close to each other along the molecular chain. In addition, the additive material 6 contains one or more metallic elements M selected from Li, Ba, Mg and Ca.

[0076] The inventors and others have conducted intensive studies, and as a result, have found that there is a particular correlation between the number of mesogenic skeletons in the epoxy resin and the characteristics of the additive material. Specifically, according to experiments by the inventors, in the case where a resin having a number of mesogenic skeletons between epoxy bonds of 0 or 1 is used as the binder, even if the additive material 6 containing the metal element M described above is added to the powder magnetic core, effective improvement in rust resistance cannot be achieved. In addition, in this case, even if the content rate of the additive material is increased to improve rust resistance, the magnetic permeability decreases, and high rust resistance and high magnetic permeability cannot be achieved simultaneously. On the other hand, in the case where an epoxy resin having a number of mesogenic skeletons between epoxy bonds of 2 or more is used as the binder 2, by adding the additive material 6 containing the metal element M to the powder magnetic core 110, high magnetic permeability and high rust resistance can be achieved simultaneously.

[0077] In addition, in the powder magnetic core 110 of the present embodiment, by setting the weight ratio R of the metal element M with respect to the total weight of the epoxy resin (binder 2), the magnetic particles 4, and the additive material 6 to be within a predetermined range M Control is within a predetermined range, and higher magnetic permeability and higher rust resistance are obtained.

[0078] The above describes an embodiment of the present application, but the present application is not limited to the above-described embodiment, and various changes can be made within the scope of the gist of the present application.

[0079] For example, electronic components such as inductor elements can also be configured by combining a plurality of powder magnetic cores. In addition, the shape of the powder magnetic core is not particularly limited, and can be, for example, a ring type, an FT type, an ET type, an EI type, a UU type, an EE type, an EER type, a UI type, a drum type, a kettle type, or a cup type. Furthermore, in the above-described embodiment, a coil is embedded in the powder magnetic core, but the arrangement of the coil is not limited to Figure 1 The coil can also be formed by winding a wire on the outside of the powder magnetic core.

[0080] The manufacturing method of the powder magnetic core is not limited to the above-described embodiment, and the powder magnetic core can be manufactured by a sheet method or injection molding, or can be manufactured by two-stage compression. In the manufacturing method based on two-stage compression, for example, after a plurality of preliminary molded bodies are produced by pre-compressing a precursor, the preliminary molded bodies and a coreless coil are combined and subjected to formal compression.

[0081] In addition, in the above-described embodiment, an inductor element 100 is described, but the powder magnetic core of the present application can also be applied to electronic components such as a reactor, a transformer, a non-contact power supply device, and a magnetic shielding part.

[0082] [Example]

[0083] The present application will be described in further detail based on specific examples below. However, the present application is not limited to the examples below.

[0084] (Experiment 1)

[0085] In Experiment 1, in order to evaluate the correlation of the binder and the metal elements in the additive material, the powder magnetic core samples of Examples 1 to 4 and Comparative Examples 1 to 17 were produced.

[0086] Example 1

[0087] First, an Fe-Si alloy powder having an average particle diameter of 25 μm was produced by a gas atomization method as a raw material powder of the magnetic particles 4. A SiO2 film having an average thickness of about 100 nm was formed on the surface of the raw material powder by heat treatment.

[0088] Next, a biphenyl type epoxy resin composed of a prepolymer was prepared. The epoxy resin has three mesogenic skeletons represented by the formula (I) between the epoxy groups at the end portions of the prepolymer. Further, by dissolving the epoxy resin and a curing agent in an acetone solvent, a coating material was obtained. At this time, the amount of the curing agent added was set to 50 parts by mass with respect to 100 parts by mass of the epoxy resin, and further, a curing accelerator was added at 1 part by mass with respect to 100 parts by mass of the epoxy resin.

[0089] Next, the coating material and the Fe-Si alloy powder described above were kneaded in a kneader to obtain a precursor for the powder magnetic core of Example 1. At this time, lithium stearate containing Li was added as the additive material 6. In addition, the ratio of the coating material and the alloy powder was adjusted so that the content of the binder 2 was 3 parts by mass with respect to 100 parts by mass of the magnetic particles.

[0090] Next, the precursor described above was put into a mold, and a molded body having a ring shape was obtained by pressing at a molding pressure of 8 MPa. In addition, after the compression molding, the epoxy resin in the molded body was cured by heating the molded body at 180°C for 3 hours to obtain the powder magnetic core sample of Example 1. Further, the powder magnetic core samples having a ring shape produced all had an outer diameter of 17.5 mm, an inner diameter of 10 mm, and a thickness (height) of about 5 mm.

[0091] Example 2

[0092] In Example 2, barium stearate containing Ba was used as the additive material 6. The powder magnetic core sample of Example 2 was produced under the same experimental conditions except for the kind of the additive material as in Example 1.

[0093] Example 3

[0094] In Example 3, magnesium stearate containing Mg was used as the additive material 6. The experimental conditions other than the kind of the additive material were the same as in Example 1, and the powder core sample of Example 3 was produced.

[0095] Example 4

[0096] In Example 4, calcium stearate containing Ca was used as the additive material 6. The experimental conditions other than the kind of the additive material were the same as in Example 1, and the powder core sample of Example 4 was produced.

[0097] Comparative Examples 1 to 5

[0098] In Comparative Examples 1 to 5, a polyimide resin having no mesogenic skeleton was used as the binder. Further, in Comparative Examples 2 to 5, powder core samples were produced using different kinds of additive materials, respectively. Specifically, as for the additive material in Comparative Examples 1 to 5, no additive material was used in Comparative Example 1, lithium stearate was used in Comparative Example 2, barium stearate was used in Comparative Example 3, magnesium stearate was used in Comparative Example 4, and calcium stearate was used in Comparative Example 5. The experimental conditions other than the above in Comparative Examples 1 to 5 were the same as in Example 1.

[0099] Comparative Examples 6 to 10

[0100] In Comparative Examples 6 to 10, a cresol type epoxy resin having no mesogenic skeleton between epoxy bonds was used as the binder. Further, in Comparative Examples 7 to 10, powder core samples were produced using different kinds of additive materials, respectively.

[0101] Specifically, as for the additive material in Comparative Examples 6 to 10, no additive material was used in Comparative Example 6, lithium stearate was used in Comparative Example 7, barium stearate was used in Comparative Example 8, magnesium stearate was used in Comparative Example 9, and calcium stearate was used in Comparative Example 10. The experimental conditions other than the above in Comparative Examples 6 to 10 were the same as in Example 1.

[0102] Comparative Examples 11 to 15

[0103] In Comparative Examples 11 to 15, a biphenyl type epoxy resin having one mesogenic skeleton between epoxy bonds was used as the binder. Further, in Comparative Examples 12 to 15, powder core samples were produced using different kinds of additive materials, respectively. Specifically, as for the additive material in Comparative Examples 11 to 15, no additive material was used in Comparative Example 11, lithium stearate was used in Comparative Example 12, barium stearate was used in Comparative Example 13, magnesium stearate was used in Comparative Example 14, and calcium stearate was used in Comparative Example 15. The experimental conditions other than the above in Comparative Examples 11 to 15 were the same as in Example 1.

[0104] Comparative Examples 16 to 17

[0105] In Comparative Examples 16 to 17, as in Example 1, a biphenyl type epoxy resin having a mesogenic skeleton of 3 between epoxy bonds was used. However, in Comparative Example 16, the powder magnetic core sample was produced without using the additive material 6. In addition, in Comparative Example 17, instead of adding the additive material containing the metal element M, zinc stearate was added. The experimental conditions other than the above in Comparative Examples 16 and 17 were the same as in Example 1.

[0106] The evaluations shown below were performed on each of the examples and comparative examples in Experiment 1.

[0107] (Measurement of the number of mesogenic skeletons)

[0108] An analysis sample for molecular structure analysis was collected from the powder magnetic core sample produced. Then, by performing NMR, FT-IR, GC / MS, LC / MS, the molecular structure of the binder was analyzed, and the number of mesogenic skeletons present between two epoxy bonds in the vicinity was determined.

[0109] (Measurement of the weight ratio R M of the metal element M)

[0110] The metal element contained in the additive material used in each of the examples and comparative examples was set to M, and the content of the metal element M contained in the powder magnetic core per unit mass was measured by ICP. Here, the content of the metal element M measured refers to the weight ratio R M of the metal element M contained in 100% of the total weight of the magnetic particles, the binder, and the additive material.

[0111] (Measurement of the magnetic permeability)

[0112] The initial magnetic permeability μi of the powder magnetic core sample of each of the examples and comparative examples was measured. After winding a 30-turn wire on the ring-shaped powder magnetic core, the initial magnetic permeability μi was measured by an LCR meter (LCR428A, manufactured by HP).

[0113] (Evaluation of rust resistance)

[0114] In order to evaluate the rust resistance of the powder magnetic core sample, a salt water spray test was performed. The salt water spray test was performed in a salt water spray tester having a W900 mm, D600 mm, H350 mm. The amount of salt water spray was set to 1.5 ± 0.5 mL / h at 80 cm 2In this condition, the salt water spray test was performed for 24 hours at 35°C. After the salt water spray was performed, ten 3 mm x 3 mm measurement sites were randomly set. Each measurement site was photographed by a camera provided with an optical microscope (magnification 50x), and the rust area ratio of each measurement site was calculated. Thereafter, the average rust area ratio of the ten measurement sites was calculated. The lower the rust area ratio, the better the rust resistance of the powder magnetic core sample was determined to be.

[0115] In this embodiment, the case where the initial magnetic permeability μι is lower than 27 and the rust area ratio is 20% or more was determined to be "Not Good: F". In addition, the case where the initial magnetic permeability μι is 27 or more and the rust area ratio is less than 20% was determined to be "Good: G", and the case where the initial magnetic permeability μι is 28.5 or more and the rust area ratio is less than 12.5% was determined to be "Very Good: VG". The evaluation results of each of the examples and comparative examples are shown in Table 1.

[0116] Table 1

[0117]

[0118] As shown in Table 1, in Comparative Examples 1 to 15 in which the binder having a mesogen skeleton number of 0 or 1 was used, even if the additive material containing Li, Ba, Mg, or Ca was added, the rust resistance was not sufficiently improved. In addition, in some of the comparative examples, although an improvement in rust resistance was seen as in Comparative Example 12, the initial magnetic permeability μι decreased with the improvement in rust resistance, and high rust resistance and high magnetic permeability could not be both satisfied.

[0119] In addition, in Comparative Example 17 in which the binder having a mesogen skeleton number of 2 or more was used, the additive material containing Zn was used, but in this comparative example, high rust resistance and high magnetic permeability could not be both satisfied. On the other hand, in Examples 1 to 4 in which the binder having a mesogen skeleton number of 2 or more was used and the additive material containing Li, Ba, Mg, or Ca was used, the rust area ratio could be reduced without decreasing the initial magnetic permeability μι. From the results, it could be proved that in the case where the epoxy resin having a mesogen skeleton number of 2 or more between the epoxy bonds was used as the binder, by adding the additive material containing a metal element selected from Li, Ba, Mg, and Ca to the powder magnetic core, high rust resistance and high magnetic permeability could be both satisfied.

[0120] (Experiment 2)

[0121] Examples 5 to 8

[0122] In Examples 5 to 8, powder magnetic core samples were produced using biphenyl type epoxy resins having different mesogenic skeleton numbers between epoxy bonds than in Example 1. In addition, in Examples 5 to 8, lithium stearate was used as the additive material 6. The experimental conditions other than the mesogenic skeleton numbers in Examples 5 to 8 were common to Example 1, and the same evaluation as in Example 1 was performed.

[0123] Examples 9 to 10

[0124] In Examples 9 to 10, powder magnetic core samples were produced using additive materials 6 having different fatty acids from Example 1. Specifically, in Example 9, lithium laurate was used, and in Example 10, lithium montanate was used. The experimental conditions other than the above in Examples 9 to 10 were common to Example 1, and the same evaluation as in Example 1 was performed.

[0125] The evaluation results of Experiment 2 are shown in Table 2.

[0126] Table 2

[0127]

[0128] As shown in Table 2, in Examples 5 to 8 in which the mesogenic skeleton numbers were changed, as in Example 1, the rust area ratio could be reduced without reducing the initial permeability μι. In addition, in Examples 9 to 10 in which the types of fatty acids were changed, as in Example 1, the rust area ratio could be reduced without reducing the initial permeability μι. Furthermore, in Experiment 2, as a representative example, an additive material containing Li was used, but in the case where an additive material containing Ba, Mg, or Ca is used, an experiment in which the mesogenic skeleton number or the type of fatty acid is changed was also performed. As a result, in the case of Ba, Mg, or Ca, the same evaluation results as those of Li shown in Table 2 were obtained.

[0129] (Experiment 3)

[0130] In Experiment 3, the influence of the metal element content derived from the additive material in the powder magnetic core was evaluated.

[0131] Example 1-1 to 1-8

[0132] In order to evaluate the influence of the weight ratio R Li of Li, the amount of lithium stearate added was changed, and eight powder magnetic core samples (Example 1-1 to Example 1-8) associated with Example 1 were produced.

[0133] The experimental conditions other than the above were the same as in Example 1 of Experiment 1. The evaluation results are shown in Table 3.

[0134] Example 2-1 to 2-8

[0135] In order to evaluate the influence of the weight ratio RBa The amount of barium stearate added was changed to produce eight kinds of powder magnetic core samples (Example 2-1 to Example 2-8) associated with Example 2, in order to evaluate the effect of the weight ratio R

[0136] The experimental conditions other than the above were the same as those of Example 2 of Experiment 1. The evaluation results are shown in Table 4.

[0137] Example 3-1 to 3-8

[0138] The amount of magnesium stearate added was changed to produce eight kinds of powder magnetic core samples (Example 3-1 to Example 3-8) associated with Example 3, in order to evaluate the effect of the weight ratio R Mg The amount of barium stearate added was changed to produce eight kinds of powder magnetic core samples (Example 2-1 to Example 2-8) associated with Example 2, in order to evaluate the effect of the weight ratio R

[0139] The experimental conditions other than the above were the same as those of Example 3 of Experiment 1. The evaluation results are shown in Table 5.

[0140] Example 4-1 to 4-8

[0141] The amount of calcium stearate added was changed to produce eight kinds of powder magnetic core samples (Example 4-1 to Example 4-8) associated with Example 4, in order to evaluate the effect of the weight ratio R Ca The amount of barium stearate added was changed to produce eight kinds of powder magnetic core samples (Example 2-1 to Example 2-8) associated with Example 2, in order to evaluate the effect of the weight ratio R

[0142] The experimental conditions other than the above were the same as those of Example 4 of Experiment 1. The evaluation results are shown in Table 6.

[0143] Comparative Example 2-1 to Comparative Example 2-5

[0144] The amount of lithium stearate added was changed to produce five kinds of powder magnetic core samples (Comparative Example 2-1 to Comparative Example 2-5) associated with Comparative Example 2 using a polyimide resin. The experimental conditions other than the above were the same as those of Comparative Example 2 of Experiment 1. The evaluation results are shown in Table 7.

[0145] Comparative Example 4-1 to Comparative Example 4-5

[0146] The amount of barium stearate added was changed to produce five kinds of powder magnetic core samples (Comparative Example 4-1 to Comparative Example 4-5) associated with Comparative Example 4 using a polyimide resin. The experimental conditions other than the above were the same as those of Comparative Example 4 of Experiment 1. The evaluation results are shown in Table 8.

[0147] Comparative Example 7-1 to Comparative Example 7-5

[0148] The amount of lithium stearate added was changed to produce five kinds of powder magnetic core samples (Comparative Example 7-1 to Comparative Example 7-5) associated with Comparative Example 7 using a cresol type epoxy resin having a mesogenic skeleton number of 0. The experimental conditions other than the above were the same as those of Comparative Example 7 of Experiment 1. The evaluation results are shown in Table 9.

[0149] Comparative Example 14-1 to Comparative Example 14-5

[0150] For Comparative Example 14 using a biphenyl type epoxy resin having a number of mesogenic skeletons of 1, the amount of magnesium stearate was also changed, and five kinds of powder magnetic core samples (Comparative Examples 14-1 to 14-5) were produced in association with Comparative Example 14. The experimental conditions other than the above were the same as those of Comparative Example 14 of Experiment 1. The evaluation results are shown in Table 10.

[0151] Comparative Example 17-1 to Comparative Example 17-5

[0152] For Comparative Example 17 using a biphenyl type epoxy resin having a number of mesogenic skeletons of 3, the amount of zinc stearate was also changed, and five kinds of powder magnetic core samples (Comparative Examples 17-1 to 17-5) were produced in association with Comparative Example 17. The experimental conditions other than the above were the same as those of Comparative Example 17 of Experiment 1. The evaluation results are shown in Table 11.

[0153] Table 3

[0154]

[0155] Table 4

[0156]

[0157] Table 5

[0158]

[0159] Table 6

[0160]

[0161] Table 7

[0162]

[0163] Table 8

[0164]

[0165] Table 9

[0166]

[0167] Table 10

[0168]

[0169] Table 11

[0170]

[0171] In Figure 3The evaluation results shown in Tables 3 to 11 are summarized in the charts. Figure 3 In the graphs, the horizontal axis is set to the initial magnetic permeability μi, and the vertical axis is set to the rust area ratio, displaying the measurement results in Tables 3 to 11. Figure 3 In the chart, the closer the indicator is to the bottom right of the chart, the higher the magnetic permeability and the better the rust resistance. The area surrounded by the dashed line is good, and the area surrounded by the dotted line is particularly good.

[0172] As shown in Tables 3 to 11 and Figure 3 As shown, in Comparative Examples 2, 4, 7, 14, and 17, increasing the amount of fatty acid salt (additive) resulted in a decreasing trend in the rust area ratio, but also a decrease in the initial magnetic permeability. That is, when using resins with a mesocrystalline framework number of 0 or 1, it is difficult to achieve both high rust resistance and high magnetic permeability even when adjusting the amount of fatty acid salt containing the metal element M (Li, Ba, Mg, or Ca). In contrast, in Examples 1 to 4, which used epoxy resins with a mesocrystalline framework number of 2 or more, adjusting the weight ratio R of the metal element M contained in the pressed magnetic core improved rust resistance. M This results in higher rust resistance and higher magnetic permeability.

[0173] Specifically, as shown in Table 3, the weight ratio R of Li in the powder-pressed magnetic core is... Li The preferred concentration is 10 ppm to 100 ppm. As shown in Table 4, the weight ratio R of Ba in the pressed powder core is... Ba The preferred concentration is 190 ppm to 600 ppm. As shown in Table 5, the weight percentage R of Mg in the pressed powder core is... Mg The preferred concentration is 30 ppm to 130 ppm. Furthermore, as shown in Table 6, the weight percentage R of Ca in the pressed powder core is... Ca The preferred concentration is 60ppm to 200ppm.

Claims

1. A powder magnetic core characterized by comprising a magnetic particle, an epoxy resin, and an additive material, the epoxy resin having at least two or more mesogenic skeletons between two epoxy bonds close to each other along a molecular chain, the additive material containing Li, a weight ratio of Li with respect to a total weight of the magnetic particle, the epoxy resin, and the additive material being 12 ppm or more and 72 ppm or less.

2. The powder magnetic core according to claim 1, characterized in that the magnetic particle is a soft magnetic metal particle having Fe as a main component.

3. A powder magnetic core characterized by comprising a magnetic particle, an epoxy resin, and an additive material, the epoxy resin having at least two or more mesogenic skeletons between two epoxy bonds close to each other along a molecular chain, the additive material containing Ba, a weight ratio of Ba with respect to a total weight of the magnetic particle, the epoxy resin, and the additive material being 195 ppm or more and 583 ppm or less.

4. The powder magnetic core according to claim 3, characterized in that the magnetic particle is a soft magnetic metal particle having Fe as a main component.

5. A powder magnetic core characterized by comprising a magnetic particle, an epoxy resin, and an additive material, the epoxy resin having at least two or more mesogenic skeletons between two epoxy bonds close to each other along a molecular chain, the additive material containing Mg, a weight ratio of Mg with respect to a total weight of the magnetic particle, the epoxy resin, and the additive material being 41 ppm or more and 123 ppm or less.

6. The powder magnetic core according to claim 5, characterized in that the magnetic particle is a soft magnetic metal particle having Fe as a main component.

7. A powder magnetic core characterized by comprising a magnetic particle, an epoxy resin, and an additive material, the epoxy resin having at least two or more mesogenic skeletons between two epoxy bonds close to each other along a molecular chain, the additive material containing Ca, a weight ratio of Ca with respect to a total weight of the magnetic particle, the epoxy resin, and the additive material being 66 ppm or more and 197 ppm or less.

8. The powder magnetic core according to claim 7, characterized in that the magnetic particle is a soft magnetic metal particle having Fe as a main component.

9. An electronic component characterized by comprising the powder magnetic core according to any one of claims 1 to 8. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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