JP7435693B2 - Resin composition for melt molding, magnetic member, coil including magnetic member, method for manufacturing magnetic member - Google Patents

Description

The present invention relates to a resin composition for melt molding, a magnetic member, a coil including the magnetic member, and a method for manufacturing the magnetic member.

2. Description of the Related Art Attempts are known to manufacture magnetic members, such as magnetic cores used in electronic devices, using various molding techniques.
As a molding technique for magnetic cores, powder molding is specifically known.

For example, Patent Document 1 describes a method for producing a dust core in which magnetic powder such as nanocrystalline magnetic powder having a nanocrystalline structure with a crystal grain size of 100 nm or less is molded and fixed.
Further, Patent Document 2 describes a dust core containing soft magnetic alloy powder, insulating resin, and insulating powder.

Here, a nanocrystalline phase is formed in the magnetic particles in the powder magnetic core manufactured by the technology described in Patent Document 1 and Patent Document 2 (in the amorphous structure of the magnetic particles, fine α -Fe crystal phase is in a dispersed state). This nanocrystalline phase is formed in the amorphous magnetic powder when compacting the amorphous magnetic powder as magnetic particles or by high heat (approximately 400° C. or higher) after compacting.
Magnetic particles in which nanocrystalline phases are formed tend to exhibit excellent magnetic properties (low core loss, etc.).

Japanese Patent Application Publication No. 2004-349585 JP 2017-34069 Publication

As described in Patent Document 1 and Patent Document 2, a magnetic member can be formed by compaction. In addition, nanocrystalline phases are formed in the magnetic particles in the powder magnetic cores described in Patent Document 1 and Patent Document 2 by high heat during or after compaction, resulting in excellent magnetic properties ( It is thought that it exhibits low iron loss, etc.).

However, due to the principle of powder compacting, there are many restrictions on the shape of the mold, etc., making it difficult to form freely. Further, in powder compacting, extremely high temperature heating of 400° C. or higher is usually required.
These issues may become a problem in the manufacturing of electronic devices, which are becoming increasingly diverse and complex (specifically, the manufacturing of magnetic components included in electronic devices), as they increase manufacturing man-hours and costs. .

The present invention has been made in view of these circumstances. An object of the present invention is to obtain a magnetic member with excellent magnetic properties by a molding method different from powder molding.

The present inventors have made repeated studies from various viewpoints and have completed the following invention.

According to the invention,
A resin composition for melt molding,
Including resin and magnetic particles,
A resin composition is provided in which the magnetic particles include iron-based particles having a nanocrystalline structure.

Further, according to the present invention,
A magnetic member molded from the above resin composition is provided.

Further, according to the present invention,
A coil is provided that includes the above magnetic member as a magnetic core or an exterior member.

Further, according to the present invention,
A melting step of heating the above resin composition to 80 to 350°C to obtain a melt;
an injection step of injecting the melt into a mold;
A method for manufacturing a magnetic member is provided, the method comprising a cooling step of cooling the melt poured into the mold.

According to the present invention, a magnetic member with excellent magnetic properties can be obtained by a molding method different from powder molding.

FIG. 2 is a diagram schematically showing a coil including a magnetic core. FIG. 2 is a diagram schematically showing a coil (different embodiment from the one shown in FIG. 1) including a magnetic core. FIG. 3 is a diagram schematically showing an integrated inductor.

Embodiments of the present invention will be described in detail below with reference to the drawings.
In all the drawings, similar components are denoted by the same reference numerals, and description thereof will be omitted as appropriate.
To avoid complication, (i) if there are multiple identical components in the same drawing, only one of them will be given a reference numeral and not all of them, or (ii) especially 2 and subsequent parts, components similar to those in FIG. 1 may not be labeled again.
All drawings are for illustrative purposes only. The shapes and dimensional ratios of each member in the drawings do not necessarily correspond to the actual article.

In this specification, the term "substantially" includes a range that takes into account manufacturing tolerances, assembly variations, etc., unless explicitly stated otherwise.
In the present specification, the notation "a to b" in the description of numerical ranges represents a range from a to b, unless otherwise specified. For example, "1 to 5% by mass" means "1 to 5% by mass".

In the description of a group (atomic group) in this specification, a description that does not indicate whether it is substituted or unsubstituted includes both those without a substituent and those with a substituent. For example, the term "alkyl group" includes not only an alkyl group without a substituent (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group).

In this specification, the expression "(meth)acrylic" represents a concept that includes both acrylic and methacrylic. The same applies to similar expressions such as "(meth)acrylate".
The term "organic group" as used herein means an atomic group obtained by removing one or more hydrogen atoms from an organic compound, unless otherwise specified. For example, a "monovalent organic group" refers to an atomic group obtained by removing one hydrogen atom from an arbitrary organic compound.

<Resin composition>
The resin composition of this embodiment is used for melt molding, that is, for producing a molded article by melt molding.
Further, the resin composition of this embodiment includes a resin and magnetic particles, and the magnetic particles include iron-based particles having a nanocrystalline structure.

In Patent Documents 1 and 2, magnetic members are manufactured by powder molding. On the other hand, in this embodiment, constraints such as the shape of the mold are relaxed by melt molding, that is, first melting the resin composition to form a molten product, and then injecting the melt into the mold. Ru.
In addition, melt molding can be carried out at a relatively low temperature (for example, 80 to 350 degrees Celsius), usually less than 400 degrees Celsius, which can simplify the process of manufacturing magnetic members, reduce costs, and suppress deterioration of the resin. There are benefits.

Note that when molding a magnetic member at a relatively low temperature of less than 400°C, a nanocrystalline phase is formed in the amorphous particles contained in the molding material during molding (and this may cause the magnetic properties to deteriorate). We cannot expect that things will improve. Therefore, in the resin composition of this embodiment, iron-based particles in which a nanocrystalline structure is formed in advance (before being subjected to molding) are used as magnetic particles. By using these magnetic particles, good magnetic properties can be obtained.

The components that the resin composition of this embodiment contains or may contain will be explained.

-Resin The resin composition of this embodiment contains resin.
The resin may be a thermosetting resin or a thermoplastic resin, and may include both.
The resin composition of this embodiment preferably contains at least a thermosetting resin as the resin. By including at least a thermosetting resin as the resin, the heat resistance of the finally obtained magnetic member can be improved. This is important in terms of reliability of electronic equipment.

Examples of thermosetting resins include epoxy resins, phenol resins, polyimide resins, bismaleimide resins, urea resins, melamine resins, polyurethane resins, cyanate ester resins, silicone resins, oxetane resins (oxetane compounds), and (meth) resins. ) Acrylate resins, unsaturated polyester resins, diallyl phthalate resins, benzoxazine resins and the like. These may be used alone or in combination of two or more.

More specifically, thermosetting resins include novolak type phenolic resins such as phenol novolak resin, cresol novolak resin, bisphenol A type novolak resin, and triazine skeleton-containing phenol novolak resin; unmodified resol phenolic resin, tung oil, and linseed. Resol-type phenolic resins such as oil-modified resol phenolic resins modified with oil, walnut oil, etc., phenolic resins such as aralkyl-type phenolic resins such as phenol aralkyl resins, biphenylaralkyl-type phenolic resins; bisphenol A-type epoxy resins, bisphenol-F type epoxy resins. Resin, bisphenol type epoxy resin such as tetramethylbisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol E type epoxy resin, bisphenol M type epoxy resin, bisphenol P type epoxy resin, bisphenol Z type epoxy resin; phenol novolak type epoxy Resin, novolac type epoxy resin such as cresol novolak type epoxy resin; biphenyl type epoxy resin, biphenylaralkyl type epoxy resin, arylalkylene type epoxy resin, naphthalene type epoxy resin, anthracene type epoxy resin, phenoxy type epoxy resin, dicyclopentadiene type Epoxy resins such as epoxy resins, norbornene type epoxy resins, adamantane type epoxy resins, fluorene type epoxy resins, trisphenylmethane type epoxy resins; resins having triazine rings such as urea resins and melamine resins; unsaturated polyester resins; Maleimide resins such as bismaleimide compounds; polyurethane resins; diallyl phthalate resins; silicone resins; benzoxazine resins; polyimide resins; polyamideimide resins; benzocyclobutene resins, novolac type cyanate resins, bisphenol A type cyanate resins, bisphenol E type cyanate resins Examples include cyanate ester resins such as cyanate resins such as resins and tetramethylbisphenol F-type cyanate resins.

Only one type of thermosetting resin may be used alone, or two or more types may be used in combination. Furthermore, even if the resins are of the same type, those having different weight average molecular weights may be used in combination. Furthermore, a certain resin and its prepolymer may be used in combination.
The thermosetting resin may be semi-cured (solid) at 25°C.

The thermosetting resin preferably contains an epoxy resin from the viewpoint of high heat resistance of the molded product and ease of controlling curing behavior. The epoxy resin may include a polyfunctional epoxy resin having two or more epoxy groups in the molecule.
Examples of the epoxy resin include one or more solid epoxy resins selected from the group consisting of trisphenylmethane type epoxy resin, dicyclopentadiene type epoxy resin, bisphenol A type epoxy resin, and tetramethylbisphenol F type epoxy resin. can be mentioned.
When the thermosetting resin contains an epoxy resin, the heat resistance of the resulting magnetic member can be made sufficiently high.

In particular, the epoxy resin preferably contains at least one selected from the group consisting of an epoxy resin containing a trisphenylmethane structure, an epoxy resin containing a biphenyl structure, and an epoxy resin containing a bisphenol A structure. It is believed that the appropriate rigidity of the structure of these epoxy resins facilitates more appropriate curing behavior and further improves moldability.

I would like to add some information about the structure of the above epoxy resin just in case.
Specifically, the epoxy resin containing a trisphenylmethane structure is an epoxy resin containing a partial structure in which three of the four hydrogen atoms of methane (CH ₄ ) are substituted with benzene rings. Note that the benzene ring here may be unsubstituted or substituted with a substituent. Examples of the substituent include a hydroxy group and a glycidyloxy group.

Specifically, the epoxy resin containing a biphenyl structure is an epoxy resin containing a structure in which two benzene rings are connected by a single bond. The benzene ring here may or may not have a substituent.

Further, the epoxy resin containing a bisphenol A structure specifically refers to an epoxy resin containing a structure in which two benzene rings are connected by -C(CH ₃ ) ₂ -. The benzene ring here may be unsubstituted or substituted with a substituent. Examples of the substituent include a hydroxy group and a glycidyloxy group.

Examples of thermoplastic resins include acrylic resins, polyamide resins (such as nylon), thermoplastic urethane resins, polyolefin resins (such as polyethylene and polypropylene), polycarbonates, and polyester resins (such as polyethylene terephthalate and polybutylene). terephthalate, etc.), polyacetal, polyphenylene sulfide, polyetheretherketone, liquid crystal polymer, fluororesin (e.g. polytetrafluoroethylene, polyvinylidene fluoride, etc.), modified polyphenylene ether, polysulfone, polyethersulfone, polyarylate, polyamideimide, polyester Examples include etherimide and thermoplastic polyimide.
By using a thermoplastic resin, fluidity and moldability may be appropriately adjusted.

When using thermoplastic resins, one type may be used alone, or two or more different types may be used in combination. Furthermore, even if the same type of resin is used, two or more types having different weight average molecular weights may be used in combination. Furthermore, a certain resin and its prepolymer may be used in combination.

The content of the resin (if multiple types of resins are included, the total amount thereof) is, for example, 0.5 to 20% by mass, preferably 1 ~15% by weight, more preferably 1~10% by weight.
Further, the content of the resin is, for example, 5 to 30 volume %, preferably 10 to 30 volume %, when the total nonvolatile components of the resin composition is 100 volume %. By setting the value within such a numerical range, moldability and mechanical properties after molding can be improved.

As one aspect, the resin composition of this embodiment preferably contains only a thermosetting resin as the resin.
Moreover, as another aspect, the resin composition of this embodiment contains both a thermosetting resin and a thermoplastic resin as resins. In this case, it is preferable to use the thermoplastic resin in an amount of about 1 to 10% by mass of the entire resin. By doing so, it is considered that the curing behavior of the resin composition can be easily made appropriate (particularly, it is easy to make it easy to make the resin composition appropriately cured after a certain period of time from the start of heating).

・Iron-based particles containing nanocrystalline structures (specific particles)
The resin composition of this embodiment includes iron-based particles having a nanocrystal structure as magnetic particles. Note that, hereinafter, these particles will also be referred to as "specific particles."
The presence of a crystalline phase and its properties can be determined by X-ray diffraction measurement or an electron microscope (for example, a transmission electron microscope (TEM)).

According to common technical knowledge, the nanocrystalline structure included in the specific particles can include an α-Fe crystal phase. Thereby, the magnetic properties can be further improved.
The size of the nanocrystalline structure is typically 1-100 nm, preferably 10-40 nm. If the size of the nanocrystalline structure is appropriate, the magnetic properties can be further improved. Note that the "size of nanocrystal structure" here refers to the diameter equivalent to a perfect circle of the nanocrystal part (area observed two-dimensionally on a TEM image) that is confirmed when a specific particle is observed with a TEM. can do.
In a specific particle, the portion other than the nanocrystal structure is usually amorphous. In other words, the specific particles are usually amorphous particles in which nanocrystalline structures are dispersed.
The crystallization rate of specific particles is not particularly limited. The crystallization rate in terms of volume fraction is, for example, about 30 to 75%, specifically about 50 to 75%.

The content of Fe (iron as an element) in the specific particles is preferably 80 to 92% by mass, more preferably 81 to 90% by mass, and even more preferably 82 to 87% by mass. When the iron-based particles contain a necessary and sufficient amount of Fe, the magnetic properties can be further improved.

In addition to Fe, the specific particles have an elemental composition of, for example, Si (silicon), Cr (chromium), C (carbon), P (phosphorus), Cu (copper), Nb (niobium), and B (boron). It is preferable that one or more elements selected from the group consisting of: When the specific particles contain one or more of these elements, for example, the generation of nanocrystals in the amorphous, the suppression of crystal growth of the generated nanocrystals, etc. are achieved, and it is more preferable. Magnetic properties can be stably obtained.

In particular, it is preferable that the specific particles contain Cu (copper).
When forming a nanocrystalline structure (typically by heating amorphous iron-based particles), the inclusion of Cu in the amorphous iron-based particles facilitates the formation of a nanocrystalline structure. As mentioned above, in the resin composition of this embodiment, a nanocrystalline structure is already formed in the magnetic particles before being subjected to melt molding. It is preferable that the specific particles contain Cu.

From the above point of view, the content of Cu (copper as an element) in the specific particles is preferably 0.1 to 10% by mass, more preferably 0.3 to 5% by mass, and even more preferably 0.5 to 5% by mass. It is 3% by mass.

In particular, it is preferable that the specific particles contain Nb (niobium) and/or B (boron).
When the specific particles contain Nb or B, crystal growth is particularly easily suppressed by stabilizing the amorphous phase, and, for example, deterioration of magnetic properties is suppressed.

When the specific particles contain Nb, the amount (proportion) of Nb in the specific particles is preferably 2 to 10% by mass, more preferably 3 to 8% by mass, and still more preferably 4 to 6% by mass.
When the specific particles contain B, the amount (ratio) of B in the specific particles is preferably 1 to 4% by mass, more preferably 2 to 4% by mass.
It is believed that by adjusting the amount of Nb and/or boron appropriately, the deterioration of the magnetic properties described above can be further suppressed.

When the specific particles contain Si, the amount (proportion) of Si in the specific particles is preferably 1 to 20% by mass, more preferably 3 to 15% by mass, and still more preferably 5 to 10% by mass. When the specific particles contain Si, there is an effect of further improving magnetic properties (high magnetic permeability, low iron loss, etc.).
When the specific particles contain Cr, the amount (ratio) in the specific particles is preferably 0.001 to 1% by mass, more preferably 0.005 to 0.5% by mass, and even more preferably 0.01 to 0. .1% by mass. When the specific particles contain Cr, there is an effect that the corrosion resistance of the specific particles is improved. This is preferable in terms of reliability of the magnetic member finally obtained.
When the specific particles contain C, the amount (ratio) in the specific particles is preferably 0.001 to 1% by mass, more preferably 0.005 to 0.5% by mass, and even more preferably 0.01 to 0. .2% by mass. Like Nb and B, C is effective in suppressing crystal growth by stabilizing the amorphous phase.
When the specific particles contain P, the amount (proportion) of P in the specific particles is preferably 0.001 to 10% by mass, more preferably 0.01 to 10% by mass, and even more preferably 0.1 to 10% by mass. It is. Like Nb and B, P is effective in suppressing crystal growth by stabilizing the amorphous phase. Moreover, it can contribute to the formation of a nanocrystal structure together with Cu.

Note that the specific particles may contain elements other than Fe, Si, Cr, C, P, Cu, Nb, and B. For example, one of the following elements: Ti, Zr, Hf, Ta, Mo, W, Co, Ni, Al, Mn, Zn, S, Sn, As, Sb, Bi, N, O, Ca, V, Mg, etc. Or it may contain two or more types. The specific particles may generally contain these elements in a range of 0 to 3% by mass.

The specific particles can be manufactured by subjecting amorphous particles to heat treatment. Specifically, by first preparing amorphous particles having the above composition and then heat-treating the amorphous particles at a high temperature (for example, about 400 to 600° C.), nanocrystals can be formed within the amorphous particles.
Further, as the specific particles, commercially available products may be used. For example, from among the magnetic particles sold by Epson Atomics Co., Ltd., those corresponding to iron-based particles containing a nanocrystalline structure can be purchased and used.

The surface of the specific particles may be subjected to some kind of surface treatment. Surface treatment can be expected to improve compatibility with resins and improve fluidity during melting.
Examples of the surface treatment include treatment with a coupling agent, plasma treatment, and the like. Surface treatment allows functional groups to be bonded to the surface of specific particles. The functional group can cover part or all of the particle surface.
The functional group can be a functional group represented by the following general formula (1).
*-O-X-R...(1)
[Wherein, R represents an organic group, X is Si, Ti, Al, or Zr, and * is one of the atoms constituting the magnetic particles. ]

The above functional group is a residue formed by surface treatment with a known coupling agent such as a silane coupling agent, a titanium coupling agent, an aluminum coupling agent, a zirconium coupling agent, etc. Preferably, it is a residue of a coupling agent selected from the group consisting of silane coupling agents and titanium coupling agents. Thereby, when the specific particles are mixed with a resin to form a resin composition, the fluidity thereof can be further improved.

When surface-treating with a coupling agent, methods include immersing specific particles in a dilute solution of the coupling agent or directly spraying the coupling agent onto the specific particles.
The amount of the coupling agent used is, for example, preferably 0.05 to 1 part by mass, more preferably 0.1 to 0.5 part by mass, per 100 parts by mass of the specific particles.
Examples of the solvent used when the coupling agent and the specific particles are reacted include methanol, ethanol, isopropyl alcohol, and the like. Further, the amount of the coupling agent used at this time is preferably 0.1 to 2 parts by mass, more preferably 0.5 to 1.5 parts by mass, per 100 parts by mass of the solvent.
The reaction time between the coupling agent and the specific particles (for example, the immersion time in a diluted solution) is preferably 1 to 24 hours.

Further, when bonding the functional groups as described above, plasma treatment may be performed in advance as part of surface treatment for specific particles. As a result, OH groups are generated on the surface of the specific particles, facilitating the bonding between the specific particles and the residue of the coupling agent via oxygen atoms. This allows the functional groups to be bonded more firmly.

The plasma treatment here is preferably oxygen plasma treatment. Thereby, the surface of specific particles can be efficiently modified with OH groups.
The pressure of the oxygen plasma treatment is not particularly limited, but is preferably 100 to 200 Pa, more preferably 120 to 180 Pa.
The flow rate of the processing gas in the oxygen plasma treatment is not particularly limited, but is preferably 1000 to 5000 mL/min, more preferably 2000 to 4000 mL/min.
The output of the oxygen plasma treatment is not particularly limited, but is preferably 100 to 500W, more preferably 200 to 400W.
The treatment time of the oxygen plasma treatment is appropriately set depending on the various conditions described above, but is preferably 5 to 60 minutes, more preferably 10 to 40 minutes.

Furthermore, argon plasma treatment may be further performed before oxygen plasma treatment. As a result, active sites for modifying OH groups can be formed on the surface of specific particles, so that modification of OH groups can be performed more efficiently.

The pressure of the argon plasma treatment is not particularly limited, but is preferably 10 to 100 Pa, more preferably 15 to 80 Pa.
The flow rate of the processing gas in the argon plasma treatment is not particularly limited, but is preferably 10 to 100 mL/min, more preferably 20 to 80 mL/min.
The output of the argon plasma treatment is preferably 100 to 500W, more preferably 200 to 400W.
The treatment time for the argon plasma treatment is preferably 5 to 60 minutes, more preferably 10 to 40 minutes.

Note that it can be confirmed, for example, using a Fourier transform infrared spectrophotometer that the specific particles and the residue of the coupling agent are bonded via oxygen atoms.
Moreover, the above-mentioned surface treatment may be applied to all particles contained in the resin composition, or only to some particles.

Moreover, another coat treatment may be performed on the base of the above-mentioned surface treatment. Such coating treatment includes treatment with an insulating material. For example, in addition to resin coating such as silicone resin, silica coating and the like may be used. By performing such a coating treatment, the insulation properties of the specific particles can be further improved. Such coating treatment may be performed as necessary, or may be omitted. This coating treatment may be applied alone, rather than as a base for the above-mentioned surface treatment.

From another point of view, it is preferable that the specific particles have a shape close to a perfect circle (perfect sphere). It is thought that this reduces friction between the particles and further improves fluidity.
Specifically, the "roundness" defined below is determined for any 10 or more (preferably 50 or more) specific particles, and the average roundness determined by averaging the values is 0. It is preferably .60 or more, and more preferably 0.75 or more.
Definition of circularity: When the contour of a specific particle is observed with a scanning electron microscope, Req is the equivalent diameter of an equal area circle determined from the contour, and Rc is the radius of the circle circumscribing the contour. /Rc value.

From the viewpoint of good fluidity and improvement of magnetic performance due to high filling, it is preferable to adjust the particle size of the specific particles as appropriate.
For example, the volume-based median diameter D1 of the specific particles is preferably 0.5 to 75 μm, more preferably 0.75 to 65 μm, and still more preferably 1 to 60 μm. By appropriately adjusting the particle size (median diameter), fluidity during molding can be further improved and magnetic performance can be further improved.

Note that D1 can be obtained by, for example, a laser diffraction/scattering type particle size distribution measuring device. Specifically, the particle size distribution curve can be obtained by dry measuring magnetic particles using a particle size distribution measuring device "LA-950" manufactured by HORIBA, and then it can be determined by analyzing this distribution curve. .

・Magnetic particles other than specific particles In addition to the above-mentioned specific particles, the resin composition of the present embodiment does not contain magnetic particles that do not fall under specific particles (magnetic particles other than specific particles) from the viewpoint of manufacturing cost etc. But that's fine.
The magnetic particles other than the specific particles preferably contain one or more elements selected from the group consisting of iron, chromium, cobalt, nickel, silver, and manganese.

The magnetic particles other than the specific particles may be a crystalline material, an amorphous material, or a mixture of these materials (excluding those falling under the specific particles). Further, for example, in addition to a single substance, it may be a solid solution, a eutectic, an alloy such as an intermetallic compound, or the like. Further, a material having one type of chemical composition may be used, or two or more types of materials having different elemental compositions may be used in combination.

In particular, as the magnetic particles other than the specific particles, those containing iron-based particles are preferred. Note that iron-based particles refer to particles whose main component is iron atoms (in which the mass of iron atoms is the largest in the chemical composition). Refers to the most common iron alloy.
More specifically, as the iron-based particles, particles that exhibit soft magnetism and have an Fe content of 85% by mass or more (soft magnetic iron-rich particles) can be used. Note that soft magnetism refers to ferromagnetism with a small coercive force, and generally, ferromagnetism with a coercive force of 800 A/m or less is called soft magnetism.

In addition, although the above description focused on iron-based particles, it goes without saying that the magnetic particles other than the specific particles may be other particles. For example, magnetic particles including Ni-based soft magnetic particles, Co-based soft magnetic particles, etc. may be used.

In particular, magnetic particles other than specific particles include pure iron, silicon steel, iron-cobalt alloy, iron-nickel alloy, iron-chromium alloy, iron-aluminum alloy, carbonyl iron, stainless steel, or one of these. Examples include composite materials containing one species or two or more species. Carbonyl iron can be preferably used from the viewpoint of availability.

Further, as an example, it is preferable that the median diameter D2 of magnetic particles other than the specific particles is smaller than the median diameter D1 of the specific particles.
Specifically, the value of D2/D1 is, for example, 0.01 to 0.9, preferably 0.02 to 0.5, more preferably 0.03 to 0.3, particularly preferably 0.03 to 0. .2. By appropriately adjusting the value of D2/D1, magnetic particles other than the specific particles will enter the spaces (gaps) created between specific particles, increasing the density of the magnetic particles when forming a magnetic member. Can be done. It is thought that this will result in further improvement in magnetic properties.
The value of D2 itself is preferably 0.5 to 15 μm, more preferably 1 to 10 μm, and still more preferably 1 to 5 μm.
The value of D1 is as described above.

The magnetic particles other than the specific particles may be subjected to some kind of surface treatment. Specifically, the surface treatment is the same as the surface treatment for specific particles.
It is preferable that the magnetic particles other than the specific particles have a shape close to a perfect circle (perfect sphere) like the specific particles.

・Properties of the magnetic particles as a whole The particle size of the magnetic particles (specific particles and other particles) is adjusted as appropriate from the viewpoint of good fluidity during melting and further improvement of magnetic performance due to high filling. It is preferable that

Specifically, the volume-based median diameter of the magnetic particles (when using multiple types of magnetic particles, the median diameter of the entire magnetic particles used) is preferably 0.5 to 75 μm, more preferably It is 0.75 to 65 μm, more preferably 1 to 60 μm. By appropriately adjusting the particle size (median diameter), fluidity during molding can be further improved and magnetic performance can be further improved.

The content of magnetic particles in the resin composition (if multiple types of magnetic particles are included, the amount of all of them) is preferably 90% by mass based on the entire solid content (nonvolatile components) of the resin composition. The content is preferably 93% by mass or more, and even more preferably 95% by mass or more. The upper limit of the content of magnetic particles in the resin composition is, for example, 99% by mass or less, from the viewpoint of realistically ensuring fluidity of the resin composition. By sufficiently increasing the content of magnetic particles, magnetic performance (magnetic permeability, iron loss, etc.) can be further improved.
In addition, on a volume basis, the content of magnetic particles in the resin composition is preferably 60 volume % or more, more preferably 70 volume % or more, based on the entire solid content (nonvolatile components) of the resin composition. Preferably it is 80% by volume or more. The upper limit of this is, for example, 95% by volume or less in order to realistically ensure the fluidity of the resin composition.

In addition, when the resin composition contains specific particles and magnetic particles other than the specific particles, the mixing ratio of the two can be set to an arbitrary ratio based on the desired magnetic properties, raw material cost, and the like.
From the point of view of improving magnetic properties, the amount of specific particles based on the total magnetic particles is preferably 10 to 100% by mass, more preferably 30 to 100% by mass, and 50 to 100% by mass. is even more preferable.
Further, the amount of the specific particles relative to the total magnetic particles is preferably 10 to 100% by volume, more preferably 30 to 100% by volume, and even more preferably 50 to 100% by volume.

- Curing agent It is preferable that the resin composition of this embodiment contains a curing agent. Thereby, the resin composition can be sufficiently cured, and further improvement in heat resistance, durability, etc. of the resulting molded product can be expected. In addition, it becomes easier to appropriately control curing behavior, and as a result, moldability can be further improved.
The curing agent may be semi-cured (solid) at 25°C.

Examples of the curing agent include aliphatic polyamines, aromatic polyamines, compounds having an amino group such as dicyamine diamide, acid anhydrides such as alicyclic acid anhydrides and aromatic acid anhydrides, and phenolic resins. A phenol compound (phenolic curing agent), an imidazole compound, etc. can be used. These are preferably used when the aforementioned resin includes an epoxy resin.
Moreover, hexamethylenetetramine or the like can be used as a curing agent. This is particularly preferably used when the aforementioned resin contains a phenolic resin such as a novolak type phenolic resin.
Moreover, an imidazole compound can be used as a curing agent. This is particularly preferably used when the aforementioned resin includes a maleimide resin.

In one embodiment, the curing agent preferably contains a phenol compound. More specifically, a phenolic curing agent containing 2 to 5 phenolic hydroxyl groups per molecule is preferred, and a phenolic curing agent containing 3 to 4 phenolic hydroxyl groups per molecule is more preferred.
When the curing agent contains a phenolic curing agent, the curability can be further improved, and further improvement in the durability of the molded product can be expected. This effect is particularly noticeable when the aforementioned resin includes an epoxy resin.

Moreover, as another aspect, it is preferable that the curing agent contains a compound having an amino group. This compound can also be used particularly when the resin contains an epoxy resin to obtain effects such as increasing curability.
More specifically, a compound having an amino group contains two or more (preferably two) amino groups and one or more (preferably 1 to 5) aromatic rings (such as a benzene ring) in one molecule. Compounds are preferred. It is thought that by including an aromatic ring, the heat resistance of the molded product can be improved. Examples of such compounds include compounds containing two or more aniline skeletons in one molecule.
More specifically, as a compound having an amino group, a compound represented by the following general formula (AM) can be mentioned.

In the general formula (AM), the definition of each atomic group is as follows.
X and Y are each independently a single bond or a divalent linking group.
R ¹ , R ² and R ³ each independently represent a monovalent organic group, a hydroxyl group or a halogen atom.
k, l and m each independently represent an integer of 0 to 4.
n is an integer greater than or equal to 0.
When a plurality of Xs exist (n is 2 or more), each X may be the same or different.
When there is a plurality of R ¹ 's (k is 2 or more), each R ¹ may be the same or different.
When there is a plurality of R ² (when l is 2 or more), each R ² may be the same or different.
When there is a plurality of R ³ (when m is 2 or more and/or when n is 2 or more), each R ³ may be the same or different.

The divalent linking groups for X and Y include linear or branched alkylene groups (preferably 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms), ether groups (-O-), carbonyl groups (- Examples include CO-), ester groups (-COO- or -OCO-), sulfonyl groups (-SO ₂ -), and groups in which two or more of these are linked.

Monovalent organic groups for R ¹ , R ² and R ³ include alkyl groups, alkenyl groups, alkynyl groups, alkylidene groups, aryl groups, aralkyl groups, alkaryl groups, cycloalkyl groups, alkoxy groups, heterocyclic groups, and carboxyl groups. Examples include groups.
Examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, heptyl group, Examples include octyl group, nonyl group, and decyl group.
Examples of the alkenyl group include an allyl group, a pentenyl group, and a vinyl group.
Examples of the alkynyl group include ethynyl group.
Examples of the alkylidene group include a methylidene group and an ethylidene group.
Examples of the aryl group include tolyl group, xylyl group, phenyl group, naphthyl group, and anthracenyl group.
Examples of the aralkyl group include benzyl group and phenethyl group.
Examples of the alkaryl group include tolyl group and xylyl group.
Examples of the cycloalkyl group include an adamantyl group, a cyclopentyl group, a cyclohexyl group, and a cyclooctyl group.
Examples of the alkoxy group include methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, s-butoxy group, isobutoxy group, t-butoxy group, n-pentyloxy group, and neopentyloxy group. , n-hexyloxy group, etc.
Examples of the heterocyclic group include an epoxy group and an oxetanyl group.

In one aspect, k, l and m are all 0. That is, in one embodiment, all benzene rings in the general formula (AM) do not have substituents other than the explicitly described atomic groups.
In one embodiment, n is preferably 0-3, more preferably 0-2.

Other examples of compounds having an amino group that can be used as curing agents include chain aliphatic compounds such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, hexamethylenediamine, 1,3-pentanediamine, and 2-methylpentamethylenediamine. Polyamine; isophorone diamine, 4,4'-methylenebiscyclohexylamine, 4,4'-methylenebis(2-methylcyclohexylamine), bis(aminomethyl)norbornane, 1,2-cyclohexanediamine, 1,3-bisaminomethyl Cycloaliphatic polyamines such as cyclohexane; m-xylylene diamine, diaminodiphenyl ether, 4,4'-cyclohexylidene dianiline, diaminodiphenylmethane, condensates of aniline and formaldehyde, condensates of chloroaniline and formaldehyde, aniline and chloroaniline Formaldehyde condensate, 4,4'-methylenebis(2-methylaniline), 4,4'-methylenebis(2-ethylaniline), 4,4'-methylenebis(2-isopropylaniline), 4,4'-methylenebis (2-chloroaniline), 4,4'-methylenebis(2,6-dimethylaniline), 4,4'-methylenebis(2,6-diethylaniline), 4,4'-methylenebis(2-isopropyl-6- methylaniline), 4,4'-methylenebis(2-ethyl-6-methylaniline), 4,4'-methylenebis(2-bromo-6-ethylaniline), 4,4'-methylenebis(N-methylaniline) , 4,4'-methylenebis(N-ethylaniline), 4,4'-methylenebis(N-sec-butylaniline), 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 4,4 '-(9-fluorenylidene)dianiline, 4,4'-(9-fluorenylidene)bis(N-methylaniline), 4,4'-diaminobenzanilide, 4,4'-oxydianiline, 2,4-bis (4-aminophenylmethyl)aniline, phenylenediamine, 4-methyl-m-phenylenediamine, 2-methyl-m-phenylenediamine, N,N'-di-sec-butyl-p-phenylenediamine, 2-chloro- p-phenylenediamine, 2,4,6-trimethyl-m-phenylenediamine, 2,4-diethyl-6-methyl-m-phenylenediamine, 4,6-diethyl-2-methyl-m-phenylenediamine, 4, 6-dimethyl-m-phenylenediamine, trimethylenebis(4-aminobenzoate) 3,5-bis(methylthio)-2,4-toluenediamine, 3,5-bis(methylthio)-2,6-toluenediamine, Examples include aromatic polyamines such as 3,3'-dichloro-4,4'-diaminobiphenyl.

When using curing agents, one type may be used alone or two or more types may be used in combination.
When a curing agent is used, its content is, for example, 0.5 to 20% by mass, and preferably 1 to 15% by mass, based on 100% by mass of the entire solid content of the resin composition.
Further, the content of the curing agent is, for example, 5 to 30 volume %, preferably 10 to 30 volume %, when the total nonvolatile components of the resin composition is 100 volume %. By setting the value within such a numerical range, moldability and mechanical properties can be improved.

- Non-magnetic particles The resin composition of the present embodiment may contain non-magnetic particles exhibiting non-magnetic properties from the viewpoint of adjusting fluidity. As the non-magnetic particles, for example, particles having a volume-based median diameter of 3 μm or less can be used. In addition, in this specification, non-magnetism refers to not having ferromagnetism.

When the resin composition contains non-magnetic particles, it exhibits higher fluidity during molding and also suppresses seepage of the resin composition during molding. Therefore, the moldability of the resin composition becomes better, and the filling properties and uniformity of the magnetic particles can be further improved. Therefore, the magnetic properties of the cured product (magnetic member) can be improved.

Furthermore, by suppressing the seepage of the resin composition, the occurrence of resin burrs and the like during molding is suppressed. In addition, it is possible to prevent the mechanical properties of the molded article from deteriorating due to the imbalance of the components of the resin composition due to seepage. Therefore, a molded body (magnetic member) with fewer molding defects can be obtained.

Examples of the material for the nonmagnetic particles include ceramic materials, glass materials, and the like. Among these, those containing ceramic materials are preferably used. Such non-magnetic particles have a high affinity with the thermosetting resin, so that the fluidity of the resin composition can be maintained.

Examples of ceramic materials include oxide ceramic materials such as silica, alumina, zirconia, titania, magnesia, and calcia; nitride ceramic materials such as silicon nitride and aluminum nitride; and carbide ceramic materials such as silicon carbide and boron carbide. Examples include ceramic materials.
Moreover, it is particularly preferable that the ceramic material contains silica. Silica has high affinity with thermosetting resins and high insulation properties, so it is useful as constituent particles of nonmagnetic particles.

The true specific gravity of the constituent material of the non-magnetic particles is preferably from 1.0 to 6.0, more preferably from 1.2 to 5.0, and more preferably from 1.5 to 4.5. More preferred. Since such non-magnetic particles have a low specific gravity, they easily flow together with the melt of the resin composition. Therefore, when the melt of the resin composition flows toward the gap between the molds during molding, the nonmagnetic particles tend to flow together with the melt. As a result, the gaps are filled with non-magnetic particles, and seepage from the gaps can be more reliably suppressed. Note that the "gap" here includes, for example, a gap (clearance) between a plunger and a cylinder of a transfer molding machine.

The volume-based median diameter of the non-magnetic particles is not particularly limited, but is typically 3 μm or less, preferably 0.1 to 2.8 μm, more preferably 0.5 to 2.5 μm. be. This particle size is a preferable particle size for preventing the above-mentioned "bleed-out" and is a particle size that easily flows together with the melt of the resin composition.

Further, the volume-based median diameter of the non-magnetic particles is preferably 3 μm or less and smaller than the median diameter of the magnetic particles, but it is more preferable that the difference is 5 μm or more, and 10 to 100 μm. More preferably, the thickness is 15 to 60 μm.

Further, the average roundness of the non-magnetic particles contained in the non-magnetic particles (this definition is the same as that of the magnetic particles) is not particularly limited, but it is preferably 0.50 to 1, and 0. More preferably, it is between .75 and 1. When the roundness is within this range, the fluidity of the resin composition can be ensured by taking advantage of the rolling of the non-magnetic particles themselves, but the non-magnetic particles tend to get stuck in gaps, etc., causing problems in the thermosetting resin. It becomes easier to suppress seepage. That is, it is possible to achieve both fluidity of the resin composition and suppression of seepage of the thermosetting resin.

When non-magnetic particles are used, the amount thereof is preferably 1 to 10% by mass, more preferably 2 to 5% by mass, based on the total nonvolatile components of the resin composition. As a result, a resin composition having higher fluidity and more reliably suppressing seepage can be obtained.

-Other components The resin composition of this embodiment may contain components other than the components mentioned above.
For example, it may contain a mold release agent (wax), a curing catalyst, a low stress agent, a coupling agent, an adhesion aid, a coloring agent, an antioxidant, a corrosion resistant agent, a dye, a pigment, a flame retardant, and the like.

Examples of the mold release agent include natural waxes such as carnauba wax, synthetic waxes, higher fatty acids such as zinc stearate, metal salts thereof, and paraffin.
Examples of the curing catalyst include those known as curing catalysts for epoxy resins. Specifically, imidazoles (more specifically, 2-methylimidazole, 2-ethyl-4-methylimidazole, etc.), amines (more specifically, benzyldimethylamine (BDMA), 2,4, Examples include tertiary amine compounds such as 6-trisdimethylaminomethylphenol (DMP-30), phosphorus compounds (more specifically, organic phosphines), and the like.

Examples of the low stress agent include silicone compounds such as polybutadiene compounds, acrylonitrile butadiene copolymer compounds, silicone oils, and silicone rubbers. When using low stress agents, only one type may be used or two or more types may be used in combination.
As the coupling agent, the above-mentioned coupling agent used for surface treatment of magnetic particles can be used. Examples include silane coupling agents, titanium coupling agents, zirconia coupling agents, aluminum coupling agents, and the like. When using coupling agents, only one type may be used or two or more types may be used in combination.

When the resin composition contains other components, the amount thereof is appropriately adjusted, for example, in the range of 0.001 to 10% by mass, when the entire solid content (nonvolatile components) of the resin composition is 100% by mass.

- Properties of resin composition, etc. The resin composition of this embodiment may be solid at room temperature of 25°C. From the viewpoint of ease of introduction into a molding device, the resin composition may be in the form of powder, granules, tablets, or the like.
When the resin composition is solid, the particle size of the resin composition is not particularly limited, but a somewhat larger particle size is preferable from the viewpoint of handling properties and the like. For example, when sieving is performed using a sieve with an opening of 180 μm according to the sieving test method specified in JIS Z 8815 (dry type, manual sieving), the particle size must be such that the percentage above the sieve is 50% or more. is preferred.

The resin composition of the present embodiment can be prepared by, for example, first (1) mixing each component using a mixer or the like, and (2) then kneading it using a roll at around 120°C for about 5 minutes to form a kneaded product. (3), and the resulting kneaded product is cooled and then pulverized. (Through the above steps, a powdered resin composition can be obtained.)
Note that, if necessary, the powdered resin composition may be compressed into granules or tablets. Thereby, a resin composition suitable for resin molding such as transfer molding is obtained. Further, by making the resin composition solid at room temperature (25°C), it is possible to improve transportability and storage property.

-Indicators related to melting and curing As one of the indicators related to melting and curing of the resin composition of the present embodiment, the flow length measured by a spiral flow test can be adopted.
The flow length of the resin composition of this embodiment measured by a spiral flow test at a temperature of 175° C. is preferably 50 cm or more, more preferably 60 cm or more, and still more preferably 70 cm or more. By adjusting the formulation etc. so that the resin composition has such a flow length, suitability for mass production can be further improved.
Note that the upper limit of the flow length is, for example, 260 cm.

In the spiral flow test, for example, a low-pressure transfer molding machine (KTS-15 manufactured by Kotaki Seiki Co., Ltd.) is used to mold a spiral flow measurement mold according to EMMI-1-66 at a mold temperature of 175°C and an injection pressure. This can be done by injecting the sealing resin composition under conditions of 6.9 MPa and curing time of 120 seconds and measuring the flow length.

<Method for manufacturing magnetic member>
The resin composition of this embodiment can be molded into a desired shape by a melt molding method. for example,
・A melting step of heating the above resin composition to 80 to 350°C to obtain a melt;
・An injection process of injecting the molten material into the mold,
- A desired magnetic member can be manufactured by the cooling step of cooling the molten material injected into the mold.
The upper limit temperature for heating is set at 350°C because at around 350°C, the resin composition can be sufficiently melted in general melt molding, and if the temperature is too high, nanocrystals in specific particles may melt. (If nanocrystals grow too much, the magnetic properties may deteriorate).

Specific examples of the melt molding method include various molding methods such as transfer molding, injection molding, extrusion molding, and press molding. Among these methods, the resin composition of this embodiment is suitable for molding by transfer molding. That is, a magnetic member can be obtained by injecting a melt of the above-described resin composition into a mold using a transfer molding apparatus and hardening the melt. The molded product can be suitably used as a magnetic component in an electric/electronic device. More specifically, the molded product is suitably used as a magnetic core and/or exterior of a coil (also called a reactor, inductor, etc. depending on the use and purpose).

Transfer molding can be carried out using a known transfer molding device as appropriate. Specifically, first, a preheated resin composition is placed in a heating chamber, also called a transfer chamber, and melted to obtain a molten product. The melt is then injected into the mold with a plunger and held there to harden the melt. Thereby, a desired molded product can be obtained.
Transfer molding is preferable to other molding methods in terms of controllability of molded product dimensions and improved shape freedom.

Various conditions in transfer molding can be set arbitrarily. For example, the preheating temperature is 60-100°C, the heating temperature during melting is 150-250°C, the mold temperature is 150-200°C, and the pressure when injecting the melted resin composition into the mold is 1-250°C. It can be adjusted appropriately between 20 MPa.

<Magnetic members, coils>
Aspects of a magnetic member formed from the resin composition of this embodiment (a magnetic member formed by curing the resin composition of this embodiment) and a coil that includes the magnetic member as a magnetic core or exterior member will be described. .

(First aspect)
FIGS. 1A and 1B are diagrams schematically showing a coil 100 (reactor) including a magnetic core made of a cured product of the resin composition of this embodiment.
FIG. 1(a) shows an outline of the coil 100 seen from the top. FIG. 1(b) shows a cross-sectional view taken along the line AA' in FIG. 1(a).

Coil 100 can include a winding 10 and a magnetic core 20, as shown in FIG. The magnetic core 20 is filled inside the winding 10, which is an air-core coil. A pair of windings 10 shown in FIG. 1(a) are connected in parallel. In this case, the annular magnetic core 20 has a structure that penetrates inside the pair of windings 10 shown in FIG. 1(b). These magnetic core 20 and winding 10 can have an integrated structure.
Note that the coil 100 may have a structure in which an insulator (not shown) is interposed between the winding 10 and the magnetic core 20 in order to ensure insulation between them.

In the coil 100, the winding 10 and the magnetic core 20 may be sealed with an exterior member 30 (sealing member). For example, by accommodating the winding 10 and the magnetic core 20 in a housing, introducing liquid resin therein, and curing the liquid resin as necessary, the winding 10 and the magnetic core 20 can be coated. An exterior member 30 may also be formed. At this time, the winding 10 may have a drawn-out part (not shown) in which the end of the winding is drawn out to the outside of the exterior member 30.

The winding 10 is usually constructed by winding a metal wire with an insulating coating applied to its surface. The metal wire preferably has high conductivity, and copper and copper alloys can be suitably used. Further, as the insulating coating, a coating such as enamel can be used. The cross-sectional shape of the winding wire may be circular, rectangular, hexagonal, or the like.

On the other hand, the cross-sectional shape of the magnetic core 20 is not particularly limited, but may be, for example, circular or polygonal such as a quadrangle or hexagon in cross-sectional view. Since the magnetic core 20 is made of, for example, a transfer molded product of the resin composition of this embodiment, it can have a desired shape.

According to the cured product of the resin composition of this embodiment, a magnetic core 20 with excellent moldability and magnetic properties can be realized. That is, the coil 100 including this magnetic core 20 is expected to have good suitability for mass production, and to have low iron loss. Moreover, since the magnetic core 20 with excellent mechanical properties can be realized, it is possible to improve the durability, reliability, and manufacturing stability of the coil 100. Therefore, the coil 100 can be used as a reactor for a booster circuit or a large current.

(Second aspect)
As an aspect other than the above-mentioned coil, an outline of a coil (inductor) including an exterior member made of a cured product of the resin composition of this embodiment will be described with reference to FIG. 2.
FIG. 2(a) shows an outline of the coil 100B viewed from the top. FIG. 2(b) shows a cross-sectional view taken along the line BB' in FIG. 2(a).

Coil 100B can include a winding 10B and a magnetic core 20B, as shown in FIG. The magnetic core 20B is filled inside the winding 10B, which is an air-core coil. A pair of windings 10B shown in FIG. 2(a) are connected in parallel. In this case, the annular magnetic core 20B has a structure that penetrates inside the pair of windings 10B shown in FIG. 2(b). These magnetic core 20B and winding wire 10B can be created individually and have a combination structure in which they are combined.
Note that the coil 100B may have a structure in which an insulator (not shown) is interposed between the winding 10B and the magnetic core 20B from the viewpoint of ensuring insulation between them.

In the coil 100B, the winding 10B and the magnetic core 20B are sealed with an exterior member 30B (sealing member). For example, the magnetic core 20B filled in the winding 10B is placed in a mold, and the resin composition of this embodiment is molded using a mold such as transfer molding to cure the resin composition. An exterior member 30B can be formed around the winding 10B and the magnetic core 20B. At this time, the winding 10B may have a drawn-out part (not shown) in which the end of the winding is drawn out of the exterior member 30B.

The winding 10B is usually constructed by winding a conductive wire with an insulating coating applied to the surface of a metal wire. The metal wire preferably has high conductivity, and copper and copper alloys can be suitably used. Further, as the insulating coating, a coating such as enamel can be used. The cross-sectional shape of the winding 10B may be circular, rectangular, hexagonal, or the like.

On the other hand, the cross-sectional shape of the magnetic core 20B is not particularly limited, but may be, for example, circular or polygonal such as a quadrangle or hexagon in cross-sectional view. For the magnetic core 20B, for example, a dust core made of magnetic powder and a binder can be used.

According to the cured product of the resin composition of this embodiment, an exterior member 30B with excellent moldability and magnetic properties can be realized, so that low magnetic loss is expected in the coil 100B including the magnetic core 20B. Moreover, since the exterior member 30B with excellent mechanical properties can be realized, it is possible to improve the durability, reliability, and manufacturing stability of the coil 100B.

(Third aspect)
As still another aspect, an overview of an integrated inductor including a magnetic core and an exterior member made of a cured product of the resin composition of this embodiment will be described with reference to FIG. 3.
FIG. 3(a) shows an outline of the structure of the integrated inductor 100C viewed from the top. FIG. 3(b) shows a cross-sectional view taken along the line CC' in FIG. 3(a).

The integrated inductor 100C can include a winding 10C and a magnetic core 20C, as shown in FIG. The magnetic core 20C is filled inside the winding 10, which is an air-core coil. The winding 10C and the magnetic core 20C are sealed with an exterior member 30C (sealing member). The magnetic core 20C and the exterior member 30C can be made of a cured product of the resin composition of this embodiment. The magnetic core 20C and the exterior member 30C may be formed as a seamless integral member.

As a method for manufacturing the integrated inductor 100C, for example, the winding 10C is placed in a mold, and the resin composition of this embodiment is used to perform mold molding such as transfer molding. Thereby, the resin composition can be cured to integrally form the magnetic core 20C filled in the winding 10C and the exterior member 30C around these. At this time, the winding 10C may have an unillustrated lead-out portion in which the end of the winding is pulled out to the outside of the exterior member 30C.

The winding wire 10C is usually constructed by winding a conductive wire with an insulating coating applied to the surface of a metal wire. The metal wire preferably has high conductivity, and copper and copper alloys can be suitably used. Further, as the insulating coating, a coating such as enamel can be used. The cross-sectional shape of the winding 10C may be circular, rectangular, hexagonal, or the like.

On the other hand, the cross-sectional shape of the magnetic core 20C is not particularly limited, but may be, for example, circular or polygonal such as a quadrangle or hexagon in cross-sectional view. Since the magnetic core 20C is made of a transfer molded product of the resin composition of this embodiment, it can have a desired shape.

According to the cured product of the resin composition of this embodiment, it is possible to realize a magnetic core 20C and an exterior member 30C with excellent moldability and magnetic properties, so that low magnetic loss is expected in the integrated inductor 100C having these. Ru. Further, since it is possible to realize the exterior member 30C with excellent mechanical properties, it is possible to improve the durability, reliability, and manufacturing stability of the integrated inductor 100C. Therefore, the integrated inductor 100C can be used as an inductor for a booster circuit or a large current.

(Supplementary information regarding magnetic members)
The average linear expansion coefficient α ₁ in the range of 50°C to 70°C of the magnetic member molded from the resin composition of the present embodiment is, for example, 30 ppm/°C or less, preferably 28 ppm/°C or less, and more Preferably it is 25 ppm/°C or less. Thereby, dimensional stability in an environment near room temperature can be improved. Note that the lower limit of the average linear expansion coefficient α ₁ in the range from 50° C. to 70° C. is not particularly limited, but is, for example, 1 ppm/° C. or more.

Further, the average linear expansion coefficient α ₂ of the magnetic member molded from the resin composition of the present embodiment in the range of 270°C to 290°C is, for example, 20 to 80 ppm/°C, preferably 22 to 75 ppm/°C. and more preferably 25 to 70 ppm/°C. By setting the average linear expansion coefficient α ₂ to be less than or equal to the above upper limit value, dimensional stability in a high temperature environment can be improved.

Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various configurations other than those described above can be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and the present invention includes modifications, improvements, etc. within a range that can achieve the purpose of the present invention.
Below, examples of reference forms will be added.
1.
A resin composition for melt molding,
Including resin and magnetic particles,
A resin composition in which the magnetic particles include iron-based particles having a nanocrystalline structure.
2.
1. The resin composition described in
A resin composition in which the content of Fe in the iron-based particles is 80 to 92% by mass.
3.
1. or 2. The resin composition described in
A resin composition in which the nanocrystalline structure includes an α-Fe crystal phase.
4.
1. ~3. The resin composition according to any one of
A resin composition in which the iron-based particles contain copper.
5.
1. ~4. The resin composition according to any one of
A resin composition in which the iron-based particles contain niobium and/or boron.
6.
5. The resin composition described in
A resin composition in which the iron-based particles contain niobium, and the content of niobium in the iron-based particles is 2 to 10% by mass.
7.
5. or 6. The resin composition described in
The resin composition, wherein the iron-based particles contain boron, and the boron content in the iron-based particles is 1 to 4% by mass.
8.
1. ~7. The resin composition according to any one of
Furthermore, the resin composition includes particles other than iron-based particles having the nanocrystalline structure as the magnetic particles.
9.
1. ~8. The resin composition according to any one of
A resin composition in which the content of the magnetic particles is 90% by mass or more based on the entire solid content of the resin composition.
10.
1. ~9. The resin composition according to any one of
A resin composition in which the magnetic particles have a volume-based median diameter of 0.5 to 75 μm.
11.
1. ~10. The resin composition according to any one of
A resin composition in which the resin includes a thermosetting resin.
12.
11. The resin composition described in
A resin composition in which the resin includes an epoxy resin.
13.
11. or 12. The resin composition described in
Furthermore, a resin composition containing a curing agent.
14.
1. ~13. A magnetic member molded from the resin composition according to any one of the above.
15.
14. A coil comprising, as a magnetic core or an exterior member, the magnetic member described in .
16.
1. ~13. A melting step of heating the resin composition according to any one of the above to 80 to 350°C to obtain a melt;
an injection step of injecting the melt into a mold;
a cooling step of cooling the molten material injected into the mold;
A method for manufacturing a magnetic member, including:

Embodiments of the present invention will be described in detail based on Examples and Comparative Examples. Note that the present invention is not limited to the examples.

<Preparation of resin composition>
The following magnetic particles, resin, curing agent, mold release agent, and curing accelerator were prepared as raw materials.

・Magnetic particles Iron-based particles 1: Magnetic powder with amorphous structure (manufactured by Epson Atomics Corporation, KUAMET6B2, median diameter D ₅₀ : 25 μm)
Iron-based particles 2: Magnetic powder containing nanocrystalline structure (α-Fe crystal phase) (manufactured by Epson Atomics Corporation, KUAMETNC1, median diameter D ₅₀ : 25 μm)
Iron-based particles 3: Carbonyl iron powder (manufactured by BASF, CIP-HQ, median diameter _D50 : 2 μm)

The alloy composition and coating treatment of each of the above magnetic particles are shown in Table 1 below.

・Resin (thermosetting resin)
Epoxy resin 1: Trisphenylmethane type epoxy resin (manufactured by Mitsubishi Chemical Corporation, E1032H60, solid at room temperature 25°C)
Epoxy resin 2: Bisphenol A epoxy resin (manufactured by Mitsubishi Chemical Corporation, YL6810, solid at room temperature 25°C)

・Curing agent Phenol resin: Novolac type phenol resin (manufactured by Sumitomo Bakelite Co., Ltd., PR-HF-3, solid at room temperature 25°C)

・Mold release agent: Synthetic wax (Ester wax WE-4, manufactured by Clariant Chemicals Co., Ltd.)

・Curing accelerator Imidazole-based curing accelerator (Curezol 2PZ-PW, manufactured by Shikoku Kasei Kogyo Co., Ltd.)

The preparation method was as follows.
First, each raw material component was mixed using a mixer according to the raw material components and their blending ratios shown in Table 2. Next, the resulting mixture was roll-kneaded to obtain a kneaded product. Thereafter, the kneaded material was cooled and pulverized to obtain a powdery resin composition.
The resin compositions of each example were sieved using a sieve with an opening of 180 μm according to the sieving test method (dry type, manual sieving) specified in JIS Z 8815. In all resin compositions, the percentage on sieve was 50% or more (roughly speaking, 50% or more of the resin compositions had a particle size of 180 μm or more).

<Evaluation>
(Iron loss (50mT, 50kHz))
The resin compositions of each example and comparative example were injected using a low-pressure transfer molding machine (KTS-30 manufactured by Kotaki Seiki Co., Ltd.) at a mold temperature of 175°C, an injection pressure of 9.8 MPa, and a curing time of 120 seconds. A ring-shaped molded product having an outer diameter of 27 mmΦ, an inner diameter of 15 mmΦ, and a thickness of 3 mm was obtained. Next, the obtained ring-shaped molded product was post-cured at 175° C. for 4 hours.
Using an AC/DC magnetization characteristic recording device (manufactured by Metron Giken Co., Ltd., MTR-3368), the ring-shaped test piece thus obtained was measured to determine the hysteresis loss Wh ( kW/m ³ ) and eddy current loss We (kW/m ³ ). Then, the sum of the hysteresis loss Wh and the eddy current loss We was calculated as iron loss (kW/m ³ ).
The smaller the iron loss value, the better the magnetic properties.

(Spiral flow test)
A spiral flow test was conducted using the resin compositions of each Example and Comparative Example.
The test was carried out using a low-pressure transfer molding machine (KTS-15 manufactured by Kotaki Seiki Co., Ltd.) in a spiral flow measurement mold according to EMMI-1-66 at a mold temperature of 175°C and an injection pressure of 6. The sealing resin composition was injected under conditions of 9 MPa and curing time of 120 seconds, and the flow length was measured.

(Glass transition temperature, average coefficient of linear expansion α ₁ (50-70℃), average coefficient of linear expansion α ₂ (270-290℃))
The obtained resin composition was injection molded using a low-pressure transfer molding machine (KTS-30 manufactured by Kotaki Seiki Co., Ltd.) at a mold temperature of 175°C, an injection pressure of 9.8 MPa, and a curing time of 120 seconds to form a 15 mm× A molded article of 4 mm x 4 mm was obtained. Next, the obtained molded article was post-cured at 175° C. for 4 hours to prepare a test piece.
Then, the obtained test piece was analyzed using a thermomechanical analyzer (TMA100, manufactured by Seiko Instruments Inc.) under the conditions of a measurement temperature range of 0°C to 400°C and a heating rate of 5°C/min. The transition temperature (°C), the average linear expansion coefficient α ₁ (ppm/°C) from 50°C to 70°C, and the average linear expansion coefficient α ₂ (ppm/°C) from 270°C to 290°C were measured.

The evaluation results are summarized in Table 3.

From Table 3, the following can be said.
・The core loss value of the magnetic member obtained by melt-molding (transfer molding) the resin compositions of Examples 1 to 3 containing iron-based particles (iron-based particles 2) containing a nanocrystalline structure is This value was smaller than the core loss value of the magnetic member obtained by melt-molding the resin composition of Comparative Example 1 which did not contain Particles 2. In other words, it was shown that the magnetic performance was improved. Further, it can be seen that the larger the amount of iron-based particles containing a nanocrystalline structure (iron-based particles 2) in the composition, the smaller the iron loss becomes.
- The resin compositions of Examples 1 to 3 had sufficiently long flow lengths in the spiral flow test. In other words, it was shown that the resin compositions of Examples 1 to 3 can be preferably used for forming magnetic members by melt molding.
- The glass transition temperature of the magnetic members obtained by molding the resin compositions of Examples 1 to 3 was equal to or higher than that of the composition of Comparative Example 1. In other words, by using iron-based particles containing a nanocrystalline structure, there were no disadvantages such as a significant decrease in the heat resistance of the magnetic member.
- The values of the average linear expansion coefficient α ₁ and the average linear expansion coefficient α ₂ of the magnetic members obtained by molding the resin compositions of Examples 1 to 3 pose particular problems in terms of dimensional accuracy of the magnetic member. It wasn't at that level.

10 Winding 20 Magnetic core 30 Exterior member 100 Coil 10B Winding 20B Magnetic core 30B Exterior member 100B Coil 10C Winding 20C Magnetic core 30C Exterior member 100C Integrated inductor

Claims (13)

A resin composition for transfer molding,
Contains a resin, magnetic particles, and a curing agent,
The magnetic particles include iron-based particles having a nanocrystalline structure, and the average circularity of the iron-based particles is 0.75 or more, as determined based on the following <How to determine average roundness>;
The content of the magnetic particles is 90% by mass or more based on the entire solid content of the resin composition,
The volume-based median diameter of the magnetic particles is 0.5 to 75 μm,
The resin includes a thermosetting resin, the thermosetting resin includes an epoxy resin,
The curing agent includes a phenol compound,
A resin composition in which the proportion of the iron-based particles in the resin composition is 16.31% by mass or more .
<How to find average roundness>
First, when the outline of the iron-based particle is observed with a scanning electron microscope, Req is the equivalent diameter of an equal area circle determined from the outline, and Rc is the radius of the circle circumscribing the outline, Req/Rc. The value of is defined as roundness.
The average circularity is determined by determining the circularity for any ten or more of the iron-based particles and averaging the values. The resin composition according to claim 1. However, this excludes the case where the iron-based particles are Fe-Si-BP alloy powder containing a crystalline phase with an average crystallite diameter of 50 nm or less. The resin composition according to claim 1 or 2,
A resin composition in which the content of Fe in the iron-based particles is 80 to 92% by mass. The resin composition according to any one of claims 1 to 3,
A resin composition in which the nanocrystalline structure includes an α-Fe crystal phase. The resin composition according to any one of claims 1 to 4,
A resin composition in which the iron-based particles contain copper. The resin composition according to any one of claims 1 to 5,
A resin composition in which the iron-based particles contain niobium and/or boron. The resin composition according to claim 6,
A resin composition in which the iron-based particles contain niobium, and the content of niobium in the iron-based particles is 2 to 10% by mass. The resin composition according to claim 6 or 7,
The resin composition, wherein the iron-based particles contain boron, and the boron content in the iron-based particles is 1 to 4% by mass. The resin composition according to any one of claims 1 to 8,
Furthermore, the resin composition includes particles other than iron-based particles having the nanocrystalline structure as the magnetic particles. The resin composition according to claim 9,
A resin composition, wherein particles other than the iron-based particles include at least one selected from the group consisting of amorphous magnetic powder and carbonyl iron powder. A magnetic member molded from the resin composition according to any one of claims 1 to 10. A coil comprising the magnetic member according to claim 11 as a magnetic core or an exterior member. A melting step of heating the resin composition according to any one of claims 1 to 10 to 80 to 350°C to obtain a melt;
an injection step of injecting the melt into a mold;
A method for manufacturing a magnetic member, comprising a cooling step of cooling the molten material injected into the mold.

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