Compression powder core and electronic component

Abstract

To provide a dust core having both high initial permeability and high rust resistance and an electronic component using the same.SOLUTION: The dust core includes soft magnetic particles, an epoxy resin, and an additive material. The epoxy resin has at least two mesogen backbones between two epoxy bonds close to each other along a molecular chain. The additive materials include one or more metallic elements selected from Li, Ba, Mg, and Ca.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a compressed powder magnetic core and an electronic component including the compressed powder magnetic core.

Background Art

[0002] Compressed powder magnetic cores used in magnetic application electronic components such as inductors and reactors are generally manufactured by kneading magnetic particles together with a binder (binding material) and compression molding. In this compressed powder magnetic core, it is known to use additives such as lubricants, antiseptics, and dispersants in order to improve characteristics such as moldability and corrosion resistance. For example, Patent Documents 1 and 2 disclose compressed powder magnetic cores to which metal soap powder is added as a lubricant.

[0003] However, additives such as those described above are non-magnetic materials. Therefore, when an additive such as that described above is added to the compressed powder magnetic core, although improvement in moldability and corrosion resistance can be expected, the magnetic properties such as magnetic permeability may conversely deteriorate. That is, the effect of improving moldability and corrosion resistance by the additive and the magnetic properties of the compressed powder magnetic core are in an inverse relationship, and in particular, it has been difficult to achieve both high magnetic permeability and high rust resistance.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a compressed powder magnetic core having both high magnetic permeability and high rust resistance, and an electronic component using the compressed powder magnetic core.

Means for Solving the Problems

[0006] To achieve the above object, the compacted powder magnetic core according to the present invention includes soft magnetic particles, an epoxy resin, and an additive, the epoxy resin has at least two or more mesogenic skeletons between two epoxy bonds adjacent along the molecular chain, the additive contains one or more metal elements M selected from Li, Ba, Mg, and Ca.

[0007] As a result of intensive studies, the inventors of the present invention have found that there is a specific relationship between the number of mesogenic skeletons in the epoxy resin and the properties of the additive, and have completed the present invention.

[0008] Specifically, according to the experiments of the inventors of the present invention, when a resin having 0 or 1 mesogenic skeleton between epoxy bonds is used as a binder, even if an additive containing the above metal element M (at least one selected from Li, Ba, Mg, and Ca) is added to the compacted powder magnetic core, effective improvement in rust resistance cannot be achieved. Also, in this case, even if the content rate of the additive is increased to improve the rust resistance, the magnetic permeability decreases, and it is impossible to achieve both high rust resistance and high magnetic permeability. On the other hand, when an epoxy resin having 2 or more mesogenic skeletons between epoxy bonds is used as a binder, by adding an additive containing the metal element M to the compacted powder magnetic core, it is possible to achieve both high magnetic permeability and high rust resistance.

[0009] When the additive contains Li, preferably, the weight ratio of Li to the total weight of the soft magnetic particles, the epoxy resin, and the additive is 10 ppm or more and 100 ppm or less.

[0010] When the additive contains Ba, preferably, the weight ratio of Ba to the total weight of the soft magnetic particles, the epoxy resin, and the additive is 190 ppm or more and 600 ppm or less.

[0011] When the additive contains Mg, preferably, the weight ratio of Mg to the total weight of the soft magnetic particles, the epoxy resin, and the additive is 30 ppm or more and 130 ppm or less.

[0012] When the additive contains Ca, preferably, the weight ratio of Ca to the total weight of the soft magnetic particles, the epoxy resin, and the additive is 60 ppm or more and 200 ppm or less.

[0013] As described above, by controlling the content rate of the metal element M in the compacted magnetic core within a predetermined range, it is possible to satisfy both a higher magnetic permeability and a higher rust resistance.

[0014] Preferably, the soft magnetic particles are metal particles mainly composed of Fe.

[0015] The compacted magnetic core of the present invention can be applied to various electronic components such as inductors, reactors, transformers, non-contact power feeding coils, and magnetic shield components, and in particular, it is preferably used as the magnetic core of an inductor.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0017] Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings.

[0018] As shown in FIG. 1, an inductor element 100 according to an embodiment of the present invention includes a compacted magnetic core 110 and a coil 120 embedded inside the compacted magnetic core 110.

[0019] The shape of the compacted powder core 110 is not particularly limited, and for example, it can be in the shape of a cylinder, an elliptical cylinder, a prism, or the like. As shown in FIG. 2, the compacted powder core 110 includes a binder 2 as a binder material, magnetic particles 4 dispersed in the binder 2, and a predetermined additive 6 (not shown), and may also include non-magnetic inorganic particles or the like. That is, the compacted powder core 110 is formed into a predetermined shape by binding a plurality of magnetic particles 4 via the binder 2. Hereinafter, the binder 2, the magnetic particles 4, and the additive 6 constituting the compacted powder core 110 will be described in detail.

[0020] The binder 2 mainly consists of a cured epoxy resin and a phenolic resin, and may also contain a small amount of organic components. Here, the "small amount of organic components" are components resulting from lubricants, curing accelerators, flexibilizers, plasticizers, dispersants, colorants, anti-settling agents, etc., and may be contained in an amount of about 1.0 part by mass or less with respect to 100 parts by mass of the epoxy resin as the main component of the binder 2.

[0021] In the present embodiment, the epoxy resin of the binder 2 is characterized by having a predetermined molecular structure. Specifically, the epoxy resin of the binder 2 has a plurality of mesogenic skeletons between two epoxy bonds adjacent along the molecular chain.

[0022] Here, the "epoxy bond" in the present embodiment means a molecular arrangement formed by the ring opening of an epoxy group existing in a prepolymer by a polymerization reaction (curing reaction). Further, the "mesogenic skeleton" is a general term for an atomic group containing a polycyclic aromatic hydrocarbon or two or more aromatic rings and having rigidity and orientation.

[0023] More specifically, the mesogenic skeleton is preferably a partial structure represented by the following formula (J).

Chemical formula

[0024] In particular, in the present embodiment, it is more preferable that the mesogenic skeleton is a partial structure represented by the following formula (I). [Chemical formula] Y and * in the above formula (I) are the same as those in the formula (J). That is, in the mesogenic skeleton represented by (I), X in the formula (J) is a single bond, and the number of Ys where functional groups (side chains such as alkyl groups, acetyl groups, and halogens) can be arranged is limited compared to the formula (J).

[0025] The mesogenic skeleton as described above is considered to enhance the lubricity between the magnetic particles 4 during the molding process and efficiently promote the rearrangement of the magnetic particles 4. Also, stacking (molecular overlap) is likely to be formed between the mesogenic skeletons after curing, and this stacking is considered to contribute to the improvement of the mechanical strength of the binder 2 and the powder compact magnetic core 110. Further, the mesogenic skeleton is also considered to reduce the thermal resistance between the magnetic particles 4. Therefore, by forming the powder compact magnetic core 110 with an epoxy resin containing the mesogenic skeleton, improvements in density, strength, relative permeability, thermal conductivity, etc. can be expected. Note that in the above, "rearrangement of the magnetic particles 4" means that the particles move due to pressure and approach the closest packing state.

[0026] In the epoxy resin of the binder 2 in the present embodiment, at least two or more (preferably 10 or less, more preferably 3 or less) mesogenic skeletons as described above are present between two epoxy bonds that are adjacent along the molecular chain. The upper limit value of the mesogenic skeleton present between the epoxy bonds is not particularly limited, and can be, for example, 100 or less. Note that the plurality of mesogenic skeletons present between adjacent epoxy bonds may be different from each other or may all have the same structure. Also, between two adjacent epoxy bonds, the plurality of mesogenic skeletons may be connected in a single bond and continuously present, or may be connected via a single or a plurality of linking groups.

[0027] Here, the "two adjacent epoxy bonds" will be described in more detail. A molecular structure having a plurality of mesogenic skeletons as described above can be realized, for example, by curing an epoxy resin having a prepolymer represented by the following formula (K).

Chemical formula

[0028] Note that the number of mesogenic skeletons present between epoxy bonds can be determined by analyzing the molecular structure of the binder 2. For example, the molecular structure of the binder 2 can be analyzed by appropriately combining 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), etc. Also, the sample for measurement may be prepared by collecting the binder 2 from the compact magnetic core 110 shown in FIG. 1.

[0029] In the present embodiment, the magnetic particles 4 may 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 rate of Fe contained in the soft magnetic metal particles per unit mass is 60 wt% or more. Examples of such soft magnetic metal particles include pure iron, Fe-Si alloys (iron-silicon), Fe-Al alloys (iron-aluminum), permalloy alloys (Fe-Ni), sendust alloys (Fe-Si-Al), Fe-Si-Cr alloys (iron-silicon-chromium), Fe-Si-Al-Ni alloys, Fe-Ni-Si-Co alloys, Fe-based amorphous alloys, Fe-based nanocrystalline alloys, etc.

[0030] Note that it is preferable that the magnetic particles 4, which are soft magnetic metal particles, do not substantially contain metal elements M such as Li, Ba, Mg, and Ca contained in the additive 6. "Do not substantially contain" means that the content rate of the metal element M contained in the soft magnetic metal particles per unit mass is less than 100 ppm.

[0031] Also, it is preferable to form an insulating coating on the surface of the soft magnetic metal particles as the magnetic particles 4. Examples of the insulating coating include a film formed by oxidation of the particle surface layer (oxide film), a phosphate coating, a silicate coating, a glass coating, BN, SiO 2 , MgO, Al 2 O 3Examples include inorganic coatings containing such substances, or organic coatings. These insulating coatings can be formed by surface treatments such as heat treatment, phosphate treatment, mechanical alloying treatment, silane coupling treatment, and hydrothermal synthesis. By forming an insulating coating on the metal magnetic particles, the high-frequency loss of the compacted magnetic core 110 can be suppressed.

[0032] The average particle size (D50) of the magnetic particles 4 is not particularly limited. For example, it can be 50 μm or less, and preferably within the range of 20 μm to 40 μm. The average particle size of the magnetic particles 4 can be measured by image analysis of the cross-section of the compacted magnetic core 110 as shown in FIG. 2. Specifically, the area of each particle included in the cross-section as shown in FIG. 2 is measured, and the equivalent circle diameter of each particle is calculated from the area value, thereby obtaining the particle size distribution of the magnetic particles 4. In this measurement, the size of the measurement field of view can be appropriately adjusted according to the particle size of the observed magnetic particles 4, and it is preferable to perform the analysis in at least 5 fields of view or more to obtain the particle size distribution.

[0033] Note that all of the magnetic particles 4 included in the compacted magnetic core 110 may be composed of the same material, or may be composed of a plurality of particle groups with different materials. Also, as shown in FIG. 2, the magnetic particles 4 may be composed of a plurality of particle groups with different particle sizes. For example, large particles 4a made of an Fe-Si-based alloy and small particles 4b made of pure iron with an average particle size smaller than that of the large particles 4a can be mixed to form the magnetic particles 4.

[0034] When the magnetic particles 4 are soft magnetic metal particles, the content of the binder 2 in the compacted 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. In the compacted magnetic core 110 of the present embodiment, by using an epoxy resin having a plurality of mesogen skeletons between epoxy bonds, the shape retention can be ensured even if the ratio of the binder 2 to the magnetic particles 4 is reduced, and high strength can be obtained.

[0035] Incidentally, the binder content can be estimated by analyzing the compacted powder core with an inductively coupled plasma atomic emission spectrometer (ICP-AES). At this time, the compacted powder core is dissolved with, for example, hydrochloric acid to prepare an analysis sample, and the binder content is calculated by estimating the intensity of the elements detected by ICP-AES.

[0036] The additive 6 is an organometallic compound containing at least one metal element M selected from Li, Ba, Mg, and Ca. Here, examples of the organometallic compound include metal alkoxides, metal complexes, fatty acid salts, etc., and fatty acid salts are preferred. When the additive 6 is a fatty acid salt, examples of the fatty acid constituting the additive 6 include stearic acid, montanic acid, lauric acid, myristic acid, ricinoleic acid, behenic acid, palmitic acid, 12-hydroxystearic acid, etc., and more preferably stearic acid, montanic acid, and lauric acid.

[0037] The state of existence of the additive 6 in the compacted powder core 110 is not particularly limited, and the additive 6 may be dispersed in the binder 2 or may adhere to the surface of the magnetic particles. This additive 6 functions as a lubricant in the manufacturing process of the compacted powder core 110 to suppress molding defects. Further, by including the additive 6 having the metal element M in the compacted powder core 110, it is possible to improve the rust resistance while suppressing a decrease in magnetic permeability.

[0038] Also, by controlling the content ratio of the metal element M in the compacted powder core 110 within a predetermined range, higher magnetic permeability and higher corrosion resistance can be obtained. Specifically, when the additive 6 contains Li, the weight ratio R of Li to the total weight (100 wt%) of the binder 2 (epoxy resin), magnetic particles 4, and additive 6 Li can be in the range of 2 ppm to 500 ppm, and preferably 10 ppm or more and 100 ppm or less.

[0039] When the additive 6 contains Ba, the weight ratio of Ba to the total weight of the binder 2, magnetic particles 4, and additive 6 is R Ba, it can be in the range of 15 ppm to 4000 ppm, preferably 100 ppm or more and 2000 ppm or less, and more preferably 190 ppm or more and 600 ppm or less.

[0040] When the additive 6 contains Mg, the weight ratio R of Mg to the total weight of the binder 2, the magnetic particles 4, and the additive 6 Mg can 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, and even more preferably 40 ppm or more.

[0041] Also, when the additive 6 contains Ca, the weight ratio R of Ca to the total weight of the binder 2, the magnetic particles 4, and the additive 6 Ca can be in the range of 5 ppm to 1400 ppm, preferably 50 ppm or more and 700 ppm or less, and more preferably 60 ppm or more and 200 ppm or less.

[0042] When the main components of the compact magnetic core 110 are the above-mentioned binder 2, magnetic particles 4, and additive 6, and no other elements such as non-magnetic ceramic particles are included, the weight ratio R of the above metal element M M (R Li , R Ba , R Mg , R Ca ) corresponds to the content of the metal element M contained in the compact magnetic core 110 per unit mass. And this weight ratio R of the metal element M M can be measured by inductively coupled plasma optical emission spectrometry (ICP) after dissolving the compact magnetic core 110 with hydrochloric acid or the like to obtain a measurement sample.

[0043] Also, the weight ratio R of the above metal element M M is based on the mass of the metal element M contained in the compact magnetic core 110 due to the additive 6. In this embodiment, components other than the additive 6 such as the magnetic particles 4 do not substantially contain the metal element M, and based on the mass of the metal element M contained in the measurement sample collected from the compact magnetic core 110, the weight ratio RM It is only necessary to calculate it. If the magnetic particles 4 contain the metal element M, the composition of the magnetic particles 4 collected from the compacted magnetic core 110 is analyzed by ICP, fluorescent X-ray analysis (XRF), etc., and the mass of the metal element M detected due to the magnetic particles 4 is subtracted to obtain the weight ratio R M It is only necessary to calculate it.

[0044] Note that the compacted magnetic core 110 may contain two or more kinds of metal elements M. That is, it may contain a plurality of kinds of additives 6. For example, lithium stearate and magnesium stearate may be added in combination as the additive 6.

[0045] Also, it is preferable that the compacted magnetic core 110 does not substantially contain other organometallic compounds that do not contain the metal element M. In particular, it is preferable that the compacted magnetic core 110 does not substantially contain an organometallic compound containing Zn. That is, the content rate of Zn contained in the compacted magnetic core 110 per unit mass is preferably 50 ppm or less. By setting the content rate of the organometallic compound having Zn as a constituent element within the above range, a decrease in magnetic permeability can be suppressed.

[0046] Next, an example of a method for manufacturing the inductor element 100 shown in FIG. 1 will be described.

[0047] First, a resin material which is a raw material of the binder 2, a raw material powder of the magnetic particles 4, and the additive 6 are prepared. The raw material powder of the magnetic particles 4 can be produced by a known powder production method. Examples of the powder production method include a gas atomization method, a water atomization method, a rotating disk method, a carbonyl method, etc. Alternatively, a ribbon obtained by a single roll method may be mechanically pulverized to produce the raw material powder. After obtaining the raw material powder of the magnetic particles 4 by the above manufacturing method, the particle size of the magnetic particles 4 can be controlled by performing sieving classification, air flow classification, etc. When forming an insulating coating on the surface of the magnetic particles 4, the raw material powder obtained above may be subjected to a surface treatment such as heat treatment, phosphate treatment, mechanical alloying treatment, silane coupling treatment, hydrothermal synthesis.

[0048] As the resin raw material of the binder 2, an epoxy resin composed of a prepolymer before curing is prepared. This epoxy resin has at least two or more mesogenic skeletons between two epoxy groups located at the ends of the prepolymer.

[0049] Then, a paint is prepared by dissolving the above epoxy resin and a phenolic 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. Also, the solvent is not particularly limited, and acetone, isopropyl alcohol (IPA), methyl ethyl ketone (MEK), butyl diglycol acetate (BCA), methanol, etc. can be used. Furthermore, a curing accelerator (curing catalyst), a flexibilizer, a plasticizer, a dispersant, a colorant, an anti-settling agent, etc. may be appropriately added to the above paint. Note that the addition amount of the curing agent may be appropriately determined according to the blending amount of the epoxy resin.

[0050] As the additive 6, a powder of an organometallic compound containing a metal element M is prepared. The average particle diameter (D50) of this organometallic compound powder is preferably about 2 μm to 15 μm, and is preferably smaller than the average particle diameter of the raw material powder of the magnetic particles 4.

[0051] Next, the raw material powder of the magnetic particles 4, the paint containing the epoxy resin, and the additive 6 are put into various kneaders such as a kneader or a twin-screw extruder and kneaded to produce a precursor for a powder core. At this time, it is preferable to blend the raw material powder and the paint so that the binder 2 is 1 to 4 parts by mass with respect to 100 parts by mass of the magnetic particles. Also, the blending ratio of the additive 6 is preferably controlled so that the weight ratio R M of the metal element M in the powder core 110 is within the above-mentioned predetermined range. Note that the additive 6 may be added to and mixed with the raw material powder of the magnetic particles 4 before the kneading step. Also, in the kneading step, non-magnetic ceramic particles, etc. may be appropriately added according to the use of the inductor element.

[0052] Next, a compressed powder core is manufactured using the above-mentioned precursor. In the case of the inductor element 100 shown in FIG. 1, the precursor is filled into a mold together with an air-core coil as an insert member and compression-molded. Thereby, a molded body having the shape of the compressed powder core to be produced is obtained, and the epoxy resin in the molded body is cured by appropriately performing a heat treatment on this molded body. The heat treatment conditions at this time are not particularly limited, and any conditions under which the epoxy resin is sufficiently cured may be used. For example, the heat treatment temperature is set to 150°C to 200°C, and the treatment time is set to 1 hour to 5 hours. The atmosphere during the heat treatment is not particularly limited, and an air atmosphere may be used.

[0053] Through the above steps, an inductor element 100 in which a coil 120 is embedded inside a compressed powder core 110 is obtained.

[0054] (Summary of this embodiment) The compressed powder core 110 of this embodiment has a binder 2 containing an epoxy resin and a phenol resin, magnetic particles 4 dispersed in the binder 2, and an additive 6. The epoxy resin contained in the binder 2 has at least two or more mesogenic skeletons between two epoxy bonds adjacent along the molecular chain. Further, the additive 6 contains one or more metal elements M selected from Li, Ba, Mg, and Ca.

[0055] As a result of intensive studies, the present inventors have found that there is a specific relationship between the number of mesogenic skeletons in the epoxy resin and the properties of the additive. Specifically, according to the experiments of the present inventors, when a resin having 0 or 1 mesogenic skeleton between epoxy bonds is used as the binder, even if the additive 6 containing the above metal element M is added to the compressed powder core, effective improvement in rust resistance cannot be achieved. Also, in this case, even if the content rate of the additive is increased to improve the rust resistance, the magnetic permeability decreases, and it is impossible to achieve both high rust resistance and high magnetic permeability. On the other hand, when an epoxy resin having 2 or more mesogenic skeletons between epoxy bonds is used as the binder 2, by adding the additive 6 containing the metal element M to the compressed powder core 110, it is possible to achieve both high magnetic permeability and high rust resistance.

[0056] Also, in the compacted magnetic core 110 of the present embodiment, the weight ratio R of the metal element M to the total weight of the epoxy resin (binder 2), magnetic particles 4, and additive 6 M is controlled within a predetermined range to obtain higher magnetic permeability and higher rust resistance.

[0057] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention.

[0058] For example, electronic components such as inductor elements may be configured by combining a plurality of compacted magnetic cores. Also, the shape of the compacted magnetic core is not particularly limited, and may be, for example, a toroidal shape, FT shape, ET shape, EI shape, UU shape, EE shape, EER shape, UI shape, drum shape, pot shape, or cup shape. Furthermore, in the above embodiment, a coil is embedded in the compacted magnetic core, but the arrangement of the coil is not limited to the configuration shown in FIG. 1, and a coil may be formed by winding a conducting wire around the outside of the compacted magnetic core.

[0059] The method for manufacturing the compacted magnetic core is also not limited to the above-described embodiments, and the compacted magnetic core may be manufactured by a sheet method or injection molding, or may be manufactured by two-stage compression. In the manufacturing method by two-stage compression, for example, after preliminarily compressing a precursor to produce a plurality of preformed bodies, these preformed bodies and an air-core coil are combined and finally compressed.

[0060] Also, in the above embodiment, the inductor element 100 has been described. However, the compacted magnetic core of the present invention is also applicable to electronic components such as reactors, transformers, non-contact power supply devices, and magnetic shield components.

Example

[0061] Hereinafter, the present invention will be described in more detail based on specific examples. However, the present invention is not limited to the following examples.

[0062] (Experiment 1) In Experiment 1, in order to evaluate the relationship between the binder and the metal elements in the additive, powder compact magnetic core samples according to Examples 1 to 4 and Comparative Examples 1 to 17 were produced.

[0063] Example 1 First, as the raw material powder of the magnetic particles 4, an Fe-Si alloy powder with an average particle size of 25 μm was produced by the gas atomization method. On the surface of this raw material powder, an SiO film with an average thickness of about 100 nm was formed by heat treatment. 2 film was formed.

[0064] Next, a biphenyl-type epoxy resin composed of a prepolymer was prepared. The epoxy resin had three mesogenic skeletons shown in formula (I) between the epoxy groups located at the ends of the prepolymer. Then, the epoxy resin and the curing agent were dissolved in an acetone solvent to obtain a paint. At this time, the addition amount of the curing agent was 50 parts by mass with respect to 100 parts by mass of the epoxy resin, and in addition, 1 part by mass of a curing accelerator was added with respect to 100 parts by mass of the epoxy resin.

[0065] Next, the above paint and the Fe-Si alloy powder were kneaded with a kneader to obtain a precursor for a powder compact magnetic core according to Example 1. At this time, lithium stearate containing Li was added as the additive 6. In addition, the mixing ratio of the paint and the alloy powder was adjusted so that the content of the binder 2 with respect to 100 parts by mass of the magnetic particles was 3 parts by mass.

[0066] Next, the above precursor was put into a mold and pressurized at a molding pressure of 8 MPa to obtain a toroidal molded body. Further, after compression molding, the molded body was heated at 180 °C for 3 hours to cure the epoxy resin in the molded body, and a powder compact magnetic core sample according to Example 1 was obtained. In addition, all of the produced toroidal powder compact magnetic core samples had an outer diameter of 17.5 mm, an inner diameter of 10 mm, and a thickness (height) of around 5 mm.

[0067] Example 2 In Example 2, barium stearate containing Ba was used as the additive 6. Except for the type of additive, the experimental conditions were the same as those in Example 1, and a dust core sample according to Example 2 was produced.

[0068] Example 3 In Example 3, magnesium stearate containing Mg was used as the additive 6. Except for the type of additive, the experimental conditions were the same as those in Example 1, and a dust core sample according to Example 3 was produced.

[0069] Example 4 In Example 4, calcium stearate containing Ca was used as the additive 6. Except for the type of additive, the experimental conditions were the same as those in Example 1, and a dust core sample according to Example 4 was produced.

[0070] Comparative Examples 1 - 5 In Comparative Examples 1 to 5, a polyimide resin having no mesogenic skeleton was used as the binder. Moreover, in Comparative Examples 2 to 5, dust core samples were produced using different types of additives, respectively. Specifically, the additives in Comparative Examples 1 to 5 were as follows: Comparative Example 1: no additive was used; Comparative Example 2: lithium stearate; Comparative Example 3: barium stearate; Comparative Example 4: magnesium stearate; Comparative Example 5: calcium stearate. The experimental conditions other than the above in Comparative Examples 1 to 5 were the same as those in Example 1.

[0071] Comparative Examples 6 - 10 In Comparative Examples 6 to 10, a cresol novolak type epoxy resin having 0 mesogenic skeletons between epoxy bonds was used as the binder. Moreover, in Comparative Examples 7 to 10, dust core samples were produced using different types of additives, respectively. Specifically, the additives in Comparative Examples 6 to 10 were as follows: Comparative Example 6: no additive was used; Comparative Example 7: lithium stearate; Comparative Example 8: barium stearate; Comparative Example 9: magnesium stearate; Comparative Example 10: calcium stearate. The experimental conditions other than the above in Comparative Examples 6 to 10 were the same as those in Example 1.

[0072] Comparative Examples 11 - 15 In Comparative Examples 11 to 15, a biphenyl-type epoxy resin having 1 mesogenic skeleton between epoxy bonds was used as the binder. Moreover, in Comparative Examples 12 to 15, powder compact magnetic core samples were prepared using different types of additives respectively. Specifically, the additives in Comparative Examples 11 to 15 were as follows: Comparative Example 11: no additive was used; Comparative Example 12: lithium stearate; Comparative Example 13: barium stearate; Comparative Example 14: magnesium stearate; Comparative Example 15: calcium stearate. The experimental conditions other than those described above in Comparative Examples 11 to 15 were the same as those in Example 1.

[0073] Comparative Examples 16 - 17 In Comparative Examples 16 to 17, a biphenyl-type epoxy resin having 3 mesogenic skeletons between epoxy bonds was used in the same manner as in Example 1. However, in Comparative Example 16, a powder compact magnetic core sample was prepared without using Additive 6. Further, in Comparative Example 17, zinc stearate was added instead of the additive containing the metal element M. The experimental conditions other than those described above in Comparative Examples 16 and 17 were the same as those in Example 1.

[0074] For each example and each comparative example in Experiment 1, the following evaluations were carried out.

[0075] (Measurement of the number of mesogenic skeletons) An analysis sample for molecular structure analysis was collected from the prepared powder compact magnetic core sample. Then, by performing NMR, FT-IR, GC / MS, and LC / MS, the molecular structure of the binder was analyzed, and the number of mesogenic skeletons existing between two adjacent epoxy bonds was specified.

[0076] (Measurement of the weight ratio R M of the metal element M) Regarding the metal element contained in the additive used in each example and each comparative example as M, the content rate of the metal element M contained per unit mass of the compacted powder core was measured by ICP. The content rate of the metal element M measured here is the weight ratio R of the metal element M contained in 100% of the total weight of the magnetic particles, the binder, and the additive. M It is.

[0077] (Measurement of permeability) Regarding the compacted powder core samples of each example and each comparative example, the initial permeability μi was measured. The initial permeability μi was measured by an LCR meter (LCR428A manufactured by HP) after winding a wire 30 turns around a toroidal-shaped compacted powder core.

[0078] (Evaluation of rust resistance) To evaluate the rust resistance of the compacted powder core sample, a salt spray test was conducted. The salt spray test was carried out in a salt spray tester with dimensions of W900mm, D600mm, and H350mm. The salt spray amount was 1.5 ± 0.5 mL / h at 80 cm 2 was set. Under these conditions, a salt spray test was conducted at 35 °C for 24 hours. After the salt spray, 10 measurement sites of 3 mm × 3 mm were randomly set. Each measurement site was photographed with a camera attached to an optical microscope (magnification 50 times), and the rust area ratio of each measurement site was calculated. Then, the average rust area ratio of the 10 measurement sites was calculated. It is judged that the lower the rust area ratio, the better the rust resistance of the compacted powder core sample.

[0079] In this example, when the initial permeability μi is less than 27 and the rust area ratio is 20% or more, it was judged as "unqualified: F". Also, when the initial permeability μi is 27 or more and the rust area ratio is less than 20%, it was judged as "good: G", and when the initial permeability μi is 28.5 or more and the rust area ratio is less than 12.5%, it was judged as "particularly good: VG". The evaluation results of each example and each comparative example are shown in Table 1.

[0080]

Table 1

[0081] As shown in Table 1, in Comparative Examples 1 to 15 using a binder having 0 or 1 mesogen skeleton, even when an additive containing Li, Ba, Mg, or Ca was added, the rust resistance was not sufficiently improved. Further, as in Comparative Example 12, in some comparative examples, an improvement in rust resistance was observed, but the initial permeability μi decreased with the improvement in rust resistance, and it was not possible to achieve both high rust resistance and high permeability.

[0082] Also, in Comparative Example 17 using a binder having 2 or more mesogen skeletons, an additive containing Zn was used, but in this comparative example as well, it was not possible to achieve both high rust resistance and high permeability. On the other hand, in Examples 1 to 4 using a binder having 2 or more mesogen skeletons and an additive containing Li, Ba, Mg, or Ca, it was possible to reduce the rust area ratio without decreasing the initial permeability μi. From these results, when using an epoxy resin having 2 or more mesogen skeletons between epoxy bonds as a binder, it was proven that by adding an additive containing a metal element selected from Li, Ba, Mg, and Ca to the dust core, both high rust resistance and high permeability can be achieved.

[0083] (Experiment 2) Examples 5 - 8 In Examples 5 to 8, dust core samples were prepared using biphenyl-type epoxy resins having mesogen skeletons different from those in Example 1 between epoxy bonds, respectively. In Examples 5 to 8, lithium stearate was used as Additive 6. The experimental conditions other than the number of mesogen skeletons in Examples 5 to 8 were the same as those in Example 1, and the same evaluation as in Example 1 was carried out.

[0084] Examples 9 - 10 In Examples 9 to 10, dust core samples were prepared using Additive 6 in which the fatty acid was different from that in 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 the same as those in Example 1, and the same evaluation as in Example 1 was carried out.

[0085] The evaluation results of Experiment 2 are shown in Table 2.

Table 2

[0086] As shown in Table 2, even in Examples 5 to 8 where the number of mesogen skeletons was changed, the rust area ratio could be reduced without decreasing the initial permeability μi, similar to Example 1. Also, even in Examples 9 to 10 where the type of fatty acid was changed, the rust area ratio could be reduced without decreasing the initial permeability μi, similar to Example 1. In Experiment 2, although an additive containing Li was used as a representative example, experiments were also conducted when using additives containing Ba, Mg, or Ca while changing the number of mesogen skeletons and the type of fatty acid. As a result, even in the case of Ba, Mg, or Ca, evaluation results similar to those of Li shown in Table 2 were obtained.

[0087] (Experiment 3) In Experiment 3, the influence of the metal element content rate derived from the additive in the compacted magnetic core was evaluated.

[0088] Examples 1 - 1 to 1 - 8 Weight ratio R of Li Li To evaluate the influence of, the addition amount of lithium stearate was changed to prepare eight types of compacted magnetic core samples (Examples 1-1 to 1-8) related to Example 1. The experimental conditions other than the above were the same as those of Example 1 in Experiment 1. The evaluation results are shown in Table 3.

[0089] Examples 2 - 1 to 2 - 8 Weight ratio R of Ba Ba To evaluate the influence of, the addition amount of barium stearate was changed to prepare eight types of compacted magnetic core samples (Examples 2-1 to 2-8) related to Example 2. The experimental conditions other than the above were the same as those of Example 2 in Experiment 1. The evaluation results are shown in Table 4.

[0090] Examples 3 - 1 to 3 - 8 Weight ratio R of Mg MgTo evaluate the influence of , eight kinds of compressed powder magnetic core samples (Examples 3-1 to 3-8) related to Example 3 were prepared by changing the addition amount of magnesium stearate. The experimental conditions other than the above were the same as those in Example 3 of Experiment 1. The evaluation results are shown in Table 5.

[0091] Examples 4 - 1 to 4 - 8 Weight ratio R of Ca Ca To evaluate the influence of , eight kinds of compressed powder magnetic core samples (Examples 4-1 to 4-8) related to Example 4 were prepared by changing the addition amount of calcium stearate. The experimental conditions other than the above were the same as those in Example 4 of Experiment 1. The evaluation results are shown in Table 6.

[0092] Comparative Examples 2 - 1 to Comparative Example 2 - 5 Regarding Comparative Example 2 using polyimide resin, five kinds of compressed powder magnetic core samples (Comparative Examples 2-1 to 2-5) related to Comparative Example 2 were prepared by changing the addition amount of lithium stearate. The experimental conditions other than the above were the same as those in Comparative Example 2 of Experiment 1. The evaluation results are shown in Table 7.

[0093] Comparative Examples 4 - 1 to Comparative Example 4 - 5 Regarding Comparative Example 4 using polyimide resin, five kinds of compressed powder magnetic core samples (Comparative Examples 4-1 to 4-5) related to Comparative Example 4 were prepared by changing the addition amount of barium stearate. The experimental conditions other than the above were the same as those in Comparative Example 4 of Experiment 1. The evaluation results are shown in Table 8.

[0094] Comparative Examples 7 - 1 to Comparative Example 7 - 5 Regarding Comparative Example 7 using a cresol novolak type epoxy resin with 0 mesogen skeletons, five kinds of compressed powder magnetic core samples (Comparative Examples 7-1 to 7-5) related to Comparative Example 7 were prepared by changing the addition amount of lithium stearate. The experimental conditions other than the above were the same as those in Comparative Example 7 of Experiment 1. The evaluation results are shown in Table 9.

[0095] Comparative Examples 14 - 1 to Comparative Example 14 - 5 Regarding Comparative Example 14 using a biphenyl-type epoxy resin with a mesogen skeleton number of 1, the amount of magnesium stearate added was changed to prepare five kinds of compacted powder magnetic core samples (Comparative Examples 14-1 to 14-5) related to Comparative Example 14. The experimental conditions other than the above were the same as those in Comparative Example 14 of Experiment 1. The evaluation results are shown in Table 10.

[0096] Comparative Examples 17 - 1 to Comparative Example 17 - 5 Regarding Comparative Example 17 using a biphenyl-type epoxy resin with a mesogen skeleton number of 3, the amount of zinc stearate added was changed to prepare five kinds of compacted powder magnetic core samples (Comparative Examples 17-1 to 17-5) related to Comparative Example 17. The experimental conditions other than the above were the same as those in Comparative Example 17 of Experiment 1. The evaluation results are shown in Table 11.

[0097]

Table 3

[0098]

Table 4

[0099]

Table 5

[0100]

Table 6

[0101]

Table 7

[0102]

Table 8

[0103]

Table 9

[0104]

Table 10

[0105]

Table 11

[0106] The evaluation results shown in Tables 3 to 11 were summarized in the graph of Fig. 3. In the graph of Fig. 3, the measurement results of Tables 3 to 11 were plotted with the initial permeability μi on the horizontal axis and the rust area ratio on the vertical axis. In the graph of Fig. 3, the closer the plot is to the lower right side of the graph, the higher the permeability and the better the rust resistance, which means that the range surrounded by the broken line is good and the range surrounded by the alternate long and short dash line is particularly good.

[0107] As shown in Tables 3 to 11 and Fig. 3, in Comparative Examples 2, 4, 7, 14, and 17, although the rust area ratio tended to decrease as the addition amount of the fatty acid salt (additive) increased, the initial permeability also decreased. That is, when using a resin with a mesogen skeleton number of 0 or 1, it is difficult to achieve both high rust resistance and high permeability even by adjusting the addition amount of the fatty acid salt containing the metal element M (Li, Ba, Mg, or Ca). On the other hand, in Examples 1 to 4 using an epoxy resin with a mesogen skeleton number of 2 or more, by adjusting the weight ratio R M of the metal element M contained in the compacted magnetic core, higher rust resistance and higher permeability were obtained.

[0108] Specifically, from the results shown in Table 3, it was found that the weight ratio R Li of Li contained in the compacted magnetic core is preferably 10 ppm to 100 ppm. From the results shown in Table 4, it was found that the weight ratio R Ba of Ba contained in the compacted magnetic core is preferably 190 ppm to 600 ppm. From the results shown in Table 5, it was found that the weight ratio R MgIt has been found that it is preferably in the range of 30 ppm to 130 ppm. Also, from the results shown in Table 6, the weight ratio R of Ca contained in the compacted magnetic core Ca It has been found that it is preferably in the range of 60 ppm to 200 ppm.

Explanation of Symbols

[0109] 100 … Inductor element 110 … Compacted magnetic core 2 … Binder 4 … Magnetic particles 4a … Large particles 4b … Small particles 120 … Coil

Claims

1. A dust core comprising soft magnetic particles, an epoxy resin, and an additive, wherein the epoxy resin has at least two or more mesogenic skeletons between two epoxy bonds adjacent along the molecular chain, the additive contains Ba, and the weight ratio of Ba to the total weight of the soft magnetic particles, the epoxy resin, and the additive is 190 ppm or more and 600 ppm or less.

2. A dust core comprising soft magnetic particles, an epoxy resin, and an additive, wherein the epoxy resin has at least two or more mesogenic skeletons between two epoxy bonds adjacent along the molecular chain, the additive contains Mg, and the weight ratio of Mg to the total weight of the soft magnetic particles, the epoxy resin, and the additive is 30 ppm or more and 130 ppm or less.

3. A dust core comprising soft magnetic particles, an epoxy resin, and an additive, wherein the epoxy resin has at least two or more mesogenic skeletons between two epoxy bonds adjacent along the molecular chain, the additive contains Ca, and the weight ratio of Ca to the total weight of the soft magnetic particles, the epoxy resin, and the additive is 60 ppm or more and 200 ppm or less.

4. The dust core according to any one of claims 1 to 3, wherein the soft magnetic particles are metal particles mainly composed of Fe.

5. An electronic component comprising the dust core according to any one of claims 1 to 4.

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