JP7735677B2 - Manufacturing method for composite magnetic thermosetting molded body - Google Patents

Description

The present invention relates to a method for manufacturing a composite magnetic thermosetting molded body.

Various types of coil components used in electronic devices and the like are known, but the most commonly used coil components are those in which a magnetic core material made of a composite magnetic material in which metal magnetic powder is dispersed in a binder resin is integrally molded with a coil or coil assembly. For example, Patent Document 1 describes an inductance component (coil component) in which a wound coil is encapsulated in a powder magnetic body made of an admixture containing soft magnetic powder and a binder, and the resulting body is pressure-molded at a molding pressure of 4.5 to 10.0 ton/ ^cm2 to form an integrated body.

Japanese Patent Application Laid-Open No. 2006-319020

In recent years, thermoforming, in which a mold is compressed and molded while the mold is heated, has become increasingly popular as a molding method for metal inductors such as coil components made from composite magnetic materials. This thermoforming method softens the composite magnetic material by heating, allowing molding at lower pressures, which increases the reliability and reduces the cost of the resulting metal inductors.

When performing this thermoforming, the practically desirable properties of a composite magnetic material are, from the perspective of both ease of feeding into a mold and ease of thermoforming, a flowable powder state when fed into a mold, and a flowable liquid state when compressed during thermoforming. Until now, efforts have been made to achieve these properties by using the characteristics of the thermosetting resin used, but in some cases it is difficult to achieve these properties using the characteristics of the thermosetting resin alone, leaving room for further improvement.

The present invention was made in consideration of the above-mentioned problems, and aims to provide a method for manufacturing a composite magnetic thermosetting molded body using a composite magnetic material that is in a flowable powder state when supplied to a mold and becomes a flowable liquid state when compressed during thermoforming.

The inventors conducted extensive research to solve the above problems and discovered that by incorporating a predetermined amount of a specific high-melting-point compound into a composite magnetic material, it is possible to create a composite magnetic material that is in a flowable powder state when fed into a mold and becomes a flowable liquid state when compressed for thermoforming. The use of this composite magnetic material makes it possible to provide a method for producing a composite magnetic thermosetting molded body that is easy to both feed the composite magnetic material into a mold and to thermoform, leading to the completion of this invention.

That is, the present invention provides a method for producing a composite magnetic thermosetting molded body, the method including a material preparation step, a compression molding step, and a thermosetting step, in which the material preparation step is a step of mixing a metal magnetic powder, a thermosetting resin, and a high-melting-point compound having a melting point of 25°C or higher but lower than 100°C and a boiling point of 160°C or higher so that the mass of the high-melting-point compound is 3.0 wt% or higher and 100 wt% or lower relative to the mass of the thermosetting resin, to obtain a powdered composite magnetic material; the compression molding step is a step of supplying this composite magnetic material to a mold adjusted to 100°C or higher to make it liquid, and compression molding the liquid at a molding pressure of 1000 kgf/ ^cm2 or lower to obtain a composite magnetic molded body; and the thermosetting step is a step of heat-treating this composite magnetic molded body, thermally curing the thermosetting resin while volatilizing and removing the high-melting-point compound, to obtain a composite magnetic thermosetting molded body.

The present invention provides a method for producing a composite magnetic thermosetting molded body that makes it easy to both supply the composite magnetic material to a mold and perform thermoforming.

1A to 1C are process diagrams (cross-sectional process views) showing an example of a method for manufacturing a composite magnetic thermosetting molded body (a composite magnetic thermosetting molded body containing a coil) according to the present embodiment. 1 is a photograph (drawing substitute photograph) showing the properties of the composite magnetic material produced in Example 1 at room temperature and after heating (100°C). The upper row shows the composite magnetic material that does not contain the specified high-melting-point compound, and the lower row shows the composite magnetic material that does contain the specified high-melting-point compound. In both cases, the right side shows the properties at room temperature and the left side shows the properties at 100°C.

The following describes an embodiment of the present invention.

In the method for producing a composite magnetic thermosetting molded body according to this embodiment, a composite magnetic material composed of a metal magnetic powder, a thermosetting resin, and a predetermined high-melting-point compound is obtained in the material preparation step, i.e., a composite magnetic material containing at least a metal magnetic powder, a thermosetting resin, and a predetermined high-melting-point compound, and in which these are the main components (a total of 90 wt % or more, preferably 95 wt % or more).
First, each material constituting this composite magnetic material will be described in detail.

<Metal magnetic powder>
The metal magnetic powder is a magnetic powder that can be obtained by a method of powdering a metal magnetic material, and contains iron as a main component. Examples of the metal magnetic material that can be used include iron and alloys containing iron (iron-silicon, iron-aluminum-silicon alloys, iron-nickel alloys, etc.). However, these are merely examples, and other metal magnetic materials may also be used. Furthermore, this metal magnetic powder may be a powder of one type of metal magnetic material, or a powder of a mixture of two or more types of metal magnetic materials.

For example, from the standpoint of magnetic properties and availability, a metal magnetic powder containing iron as the primary component and chromium (Cr), silicon (Si), nickel (Ni), aluminum (Al), cobalt (Co), carbon (C), boron (B), etc. as secondary components may be used. Amorphous metal powder or pure iron powder may also be used. Specific examples include alloy powders such as Fe-Ni (permalloy), Fe-Si (silicon steel), Fe-Al, Fe-Co (permendur), Fe-Si-Cr, Fe-Al-Cr, and Fe-Si-Al (sendust), as well as non-crystalline metal powders such as Fe-Si-B-Cr amorphous powder and crystalline iron powders such as carbonyl iron powder. Furthermore, among the above materials, materials that can be formed into approximately spherical metal magnetic powder (such as Fe-Si-B-Cr amorphous powder or Fe-Si-Cr alloy powder) may also be used. This is because it makes it easier to compress and mold composite magnetic materials containing this metal magnetic powder.

The iron content, which is the main component of the metal magnetic powder, is preferably 85 wt% or more, and more preferably 86 wt% or more. It may also contain one or more of the above-mentioned minor components, with the remainder being iron and unavoidable impurities.

The chromium content of this metal magnetic powder may be 2 wt % or more and 10 wt % or less, or 2.5 wt % or more and 8 wt % or less.
Chromium easily combines with oxygen in the air to form _chemically stable oxides (e.g., _Cr2O3 ). Therefore, composite magnetic thermosetting molded bodies containing chromium have particularly excellent corrosion resistance. Furthermore, because chromium oxide has a high resistivity, a chromium oxide layer is formed near the surface of the particles that make up the composite magnetic thermosetting molded body, making it easier to insulate the particles from each other.
Therefore, by setting the chromium content within the above range, it is possible to obtain a metal magnetic powder that can be used to form a composite magnetic material that has excellent corrosion resistance and can be used to manufacture coil components and the like with smaller eddy current loss.

For the same reason, the nickel content of this metal magnetic powder may be 2 wt% or more and 10 wt% or less, or 2.5 wt% or more and 8 wt% or less. Similarly, the aluminum content of this metal magnetic powder may be 2 wt% or more and 10 wt% or less, or 2.5 wt% or more and 8 wt% or less.

Furthermore, the silicon content of this metal magnetic powder may be 2 wt % or more and 10 wt % or less, or may be 3 wt % or more and 8 wt % or less.
Silicon is a component that can increase the relative permeability of coil components and the like obtained using a composite magnetic thermosetting molded body containing a metal magnetic powder. Furthermore, when a metal magnetic powder contains silicon, the specific resistance increases, so silicon is also a component that can suppress interparticle eddy current loss. Therefore, by setting the silicon content within the above range, a metal magnetic powder can be obtained that can constitute a composite magnetic material that can be used to manufacture coil components and the like with high relative permeability and low eddy current loss.

The metal magnetic powder may also contain at least one element selected from the group consisting of boron (B), titanium (Ti), vanadium (V), manganese (Mn), copper (Cu), gallium (Ga), germanium (Ge), zirconium (Zr), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and tantalum (Ta) as an element having a lower content than the above elements. In this case, the total content of these elements is preferably 5 wt% or less.
Furthermore, it may contain components such as phosphorus (P) and sulfur (S) that are inevitably mixed in during the manufacturing process, but in that case, the total content of these components is preferably 1 wt % or less.

The average particle diameter ( _D50 ) of the metal magnetic powder is preferably 1 μm or more and 30 μm or less, and more preferably 2 μm or more and 25 μm or less. Furthermore, the particle shape of the metal magnetic powder is preferably approximately spherical (for example, a shape of an approximately spherical body with the major axis divided by the minor axis being 2 or less, or even 1.5 or less), because this makes it easier to compress and mold a composite magnetic material containing this metal magnetic powder.

Here, the term "average particle diameter ( _D50 )" refers to the powder diameter (median diameter) at an integrated value of 50% in a volumetric particle size distribution determined using a particle size distribution measuring device by a laser diffraction/scattering method (microtrack method). In the case where the particles are aggregated, the term refers to the particle diameter of the aggregates. A specific example of an instrument for measuring the average particle diameter ( _D50 ) is the laser diffraction/scattering particle size distribution measuring device (particle size distribution) LA-960 (manufactured by HORIBA Seisakusho).

Furthermore, it is preferable to use a metal magnetic powder obtained by powdering a metal magnetic material using a water atomization method or a gas atomization method.
Here, the "water atomization method" refers to a method of producing metal powder by colliding molten metal with water (atomized water) sprayed at high speed, thereby pulverizing the molten metal and cooling it.
The "gas atomization method" is a method in which a jet stream of inert gas or air is blown onto the flow of molten metal from the surrounding area to pulverize the flow of molten metal, solidify it, and turn it into metal powder.

Metal magnetic powder produced by water atomization or gas atomization has a roughly spherical shape (close to a sphere), so when a composite magnetic material containing this metal magnetic powder is used to produce a composite magnetic thermosetting molded body, the filling rate can be easily increased. Furthermore, this makes it easier to compress and mold composite magnetic materials containing this metal magnetic powder. As a result, it is easier to obtain a composite magnetic thermosetting molded body with higher density and higher relative magnetic permeability.

Furthermore, this metal magnetic powder may be one that has been dried to remove water adsorbed to the powder surface, i.e., a metal magnetic dry powder obtained by drying the powder. Examples of powder drying methods include hot air treatment and dry heat treatment, and examples of drying conditions include treatment at a temperature of 100°C to 150°C for 30 minutes to 120 minutes.

This metal magnetic powder may also be surface-treated with a silane or titanium coupling agent to improve wettability with thermosetting resins. In other words, surface-treated metal magnetic powder obtained by surface-treating powder with a silane or titanium coupling agent may be used. From the perspective of affinity with the thermosetting resin, as described below, it is preferable to use a silane or titanium coupling agent having an epoxy group, amino group, or isocyanate group as a functional group. Examples of methods for surface-treating the powder include a dry treatment method in which a solution containing a coupling agent is dripped or sprayed onto the powder while stirring it in a mixer, and a wet treatment method in which a solvent is added to the powder to form a slurry, a solution containing a coupling agent is added to the slurry, and the slurry is stirred, followed by filtration and drying. This surface treatment may also be performed in combination with the drying treatment described above.

Furthermore, this metal magnetic powder may be one that has been phosphate-treated to coat the surface with an insulating film, i.e., a phosphate-treated metal magnetic powder obtained by phosphate-treating the powder with a phosphate. Examples of phosphates include zinc phosphate, zinc-calcium phosphate, manganese phosphate, and iron phosphate. From the perspective of ease of forming an insulating film with magnetic powders whose main component is iron, zinc phosphate is particularly preferable. Examples of methods for phosphate-treating the powder include acid washing or water washing, as necessary, followed by phosphate treatment, followed by water washing and drying. This phosphate treatment may also be performed in combination with the drying process described above.

The content of this metal magnetic powder in the composite magnetic material obtained in the material preparation process is preferably 90 wt% or more and 98.5 wt% or less, more preferably 92 wt% or more and 98 wt% or less, and even more preferably 94 wt% or more and 97.5 wt% or less.

<Thermosetting resin>
Thermosetting resins are reactive resin compositions primarily composed of functional prepolymers. They soften and flow upon heating, gradually forming a three-dimensional network structure through a crosslinking reaction, and then harden. The composite magnetic thermosetting molded body obtained by the method for manufacturing a composite magnetic thermosetting molded body according to this embodiment contains a thermosetting resin composition. In this invention, this thermosetting resin may also be referred to as a "thermosetting resin." The thermosetting resin may function as a binder resin and be cured by heating (e.g., resins used in semiconductor encapsulation materials). Examples of suitable thermosetting resins include epoxy resins (e.g., bisphenol, naphthalene, novolac, aliphatic, and glycidylamine), silicone resins (e.g., methylphenyl silicone resins), phenolic resins (e.g., novolac and resol), polyamide resins, polyimide resins, melamine resins, and polyphenylene sulfide resins. Mixtures of two or more thermosetting resins may also be used. In particular, from the viewpoint of heat resistance, it is more preferable to use an epoxy resin.
Although not limited thereto, it is preferable that the thermosetting resin be softened by being held for a predetermined time (for example, about 10 to 120 seconds) in a temperature range of 50 to 140° C. Furthermore, although not limited thereto, it is preferable that the thermosetting resin be hardened by being held for a predetermined time (for example, about 0.1 to 5 hours) in a temperature range of 150° C. or higher.

Furthermore, from the viewpoint of ease of thermosetting, it is preferable that this thermosetting resin be mixed with a curing agent. As the curing agent, a phenol novolac type curing agent (such as a phenol novolac resin or a bisphenol A novolac resin), a polyamide type curing agent (such as a polyamide resin), an acid anhydride type curing agent such as maleic anhydride or phthalic anhydride, a latent amine type curing agent such as dicyandiamide or imidazole, or an aromatic amine such as diaminodiphenylmethane or diaminodiphenylsulfone can be used. These curing agents can be used alone or in combination of two or more.
Furthermore, other additives such as a diluent, a filler, a mold release agent, etc. may be mixed in the composition within the range that does not affect the effects of the present invention.

When preparing the composite magnetic material, a solvent may be mixed with the thermosetting resin to form a solution containing the thermosetting resin. This solvent is removed by drying or other methods in the processes described below (e.g., the material preparation process), but from the perspective of ease of removal, it is preferable to use a small amount of solvent (e.g., the ratio of the volume of solvent to the total volume of raw materials used in the composite magnetic material excluding the solvent is less than 5.0 vol%, or even 0.5 vol% to 2.0 vol%). The solvent is preferably one that can be removed by drying or other methods in the processes described below, and suitable examples include organic solvents such as alcohol, toluene, chloroform, methyl ethyl ketone, acetone, and ethyl acetate.

The content of this thermosetting resin in the composite magnetic material obtained in the material preparation process is preferably 1.5 wt% or more and 5.0 wt% or less, more preferably 2.0 wt% or more and 4.5 wt% or less, and even more preferably 2.5 wt% or more and 4.0 wt% or less.

<High melting point compound>
The high-melting-point compound is a compound having a melting point of 25°C or higher but less than 100°C and a boiling point of 160°C or higher. Because this high-melting-point compound is solid at room temperature (20±5°C), a composite magnetic material containing a predetermined amount of this high-melting-point compound exhibits good powder fluidity when supplied to a mold. In other words, it becomes a flowable powder. Furthermore, this high-melting-point compound becomes liquid at temperatures above 100°C, and is included in a mass range described below relative to the mass of the thermosetting resin that softens upon heating. Therefore, the composite magnetic material becomes a flowable liquid when compressed during thermoforming. Regardless of the characteristics of the thermosetting resin contained in the composite magnetic material, the above-described properties can be achieved by including a predetermined amount of this high-melting-point compound in the composite magnetic material. Furthermore, because this high-melting-point compound has a boiling point of 160°C or higher, it is unlikely to volatilize below 40°C, ensuring the shelf life of a composite magnetic material containing a predetermined amount of this compound at temperatures below 40°C (e.g., between 10°C and 40°C). Furthermore, the volatilization of the high-melting-point compound can be suppressed during the material preparation process and compression molding process described below.

Although not limited, the melting point of this high-melting-point compound is preferably above 35°C, even more preferably 45°C or higher, and even more preferably 49°C or higher. The upper limit of the melting point is more preferably 80°C or lower, and even more preferably 75°C or lower. Although not limited, the boiling point is more preferably 170°C or higher, even more preferably 180°C or higher, even more preferably 200°C or higher, and even more preferably 210°C or higher. In order to facilitate the removal of the high-melting-point compound in the thermal curing process described below, the upper limit of the boiling point is more preferably 330°C or lower, even more preferably 310°C or lower, and even more preferably 300°C or lower.

Examples of such high-melting-point compounds include cyclohexanol, p-cresol, phenol, L-menthol (menthol), benzophenone, α,α'-dichloro-o-xylene, stearyl alcohol, 3,5-dimethylphenol, butylhydroxytoluene, and coumarin. One or more compounds selected from this group can be used, and two or more compounds can also be used in combination. From the standpoints of manufacturability and cost, it is particularly preferable to use butylhydroxytoluene and/or coumarin as the high-melting-point compound.

The mass of the high-melting-point compound in the composite magnetic material obtained in the material preparation step is set to 3.0 wt % or more and 100 wt % or less of the mass of the thermosetting resin contained in the composite magnetic material. The lower limit is preferably 5.0 wt % or more, more preferably 7.0 wt % or more, and even more preferably 10 wt % or more. The upper limit is preferably 80 wt % or less, more preferably 60 wt % or less, even more preferably 50 wt % or less, and even more preferably 33 wt % or less.
The content of this high-melting point compound in the total mass of the composite magnetic material obtained in the material preparation process may be 0.05 wt% or more and 5.0 wt% or less, or even 0.1 wt% or more and 3.0 wt% or less, or even 0.3 wt% or more and 1.0 wt% or less.

When preparing the composite magnetic material, the high-melting-point compound may be mixed with a solvent similar to that used for the thermosetting resin described above. Alternatively, the thermosetting resin and high-melting-point compound may be mixed together with the solvent. The type and mixing ratio of the solvent may be the same as those described above.

A powdered composite magnetic material is prepared using such metal magnetic powder, a thermosetting resin, and a specified high-melting point compound, but the composite magnetic material may also be prepared by mixing other components (e.g., dispersants, plasticizers, lubricants, etc.) within a range that does not affect the effects of the present invention.
This powdered composite magnetic material may be granulated into a granulated powder (granulated powder of composite magnetic material) because it can be more easily supplied to a mold.

<Method for manufacturing composite magnetic thermosetting molded body>
Next, each step of the manufacturing method of the composite magnetic thermosetting molded body according to this embodiment will be described in detail.

The method for manufacturing a composite magnetic thermosetting molded body according to this embodiment includes at least the following material preparation step, compression molding step, and thermosetting step. Note that the composite magnetic thermosetting molded body manufactured by this manufacturing method includes not only non-embedded type magnetic core materials that do not have a coil or the like embedded therein, but also coil components that have a coil embedded therein.
Each of the above steps will be described in detail below.

[Material preparation process]
The material preparation process is a process for obtaining a powdered composite magnetic material composed of a metal magnetic powder, a thermosetting resin, and a predetermined high-melting-point compound. Specifically, the metal magnetic powder, thermosetting resin, and high-melting-point compound described above are prepared. The metal magnetic powder is mixed and dispersed in the thermosetting resin and the high-melting-point compound (e.g., a solution of these with a solvent added) using a mixer or the like, granulated if necessary, and then dried to prepare a powdered composite magnetic material (powder or granulated powder of the composite magnetic material). If necessary, dispersants, plasticizers, etc. may be added as appropriate before mixing and dispersing. The mass of the high-melting-point compound in the composite magnetic material is adjusted to be 3.0 wt % or more and 100 wt % or less of the mass of the thermosetting resin contained in the composite magnetic material.

While there are no limitations on the order in which the metal magnetic powder, thermosetting resin, high-melting-point compound, and solvent are mixed, it is preferable to mix the metal magnetic powder (and other materials) into a solution obtained by mixing the high-melting-point compound, thermosetting resin, and solvent from the perspective of ease of mixing and dispersion. The above mixing may be performed by kneading and granulation. Furthermore, when obtaining granulated powder of the composite magnetic material by granulation, classification may be performed after granulation or drying. Examples of classification methods include dry classification such as sieving classification, inertial classification, and centrifugal classification, and wet classification such as sedimentation classification. If a solvent is used, it is preferable to dry the mixture after mixing to reduce the solvent content to approximately 0 vol%. Furthermore, it is preferable to perform this material preparation process in an environment with an ambient temperature of room temperature (20±5°C).

[Compression molding process]
The compression molding process is a process in which the composite magnetic material obtained in the material preparation process is compression-molded under specified conditions to obtain a composite magnetic molded body. Specifically, the mold of the press machine is first adjusted to 100°C or higher (a temperature above the melting point of the high-melting-point compound contained in the composite magnetic material). The composite magnetic material is then supplied into the mold through an opening in the mold using an injector or the like to liquefy it. The shape and size of the mold are not particularly limited. Furthermore, when the composite magnetic material is poured into the mold, vibration may be applied to prevent areas inside the mold from being insufficiently filled with the composite magnetic material. Here, making the composite magnetic material "liquid" means that it has fluidity containing a liquid or paste, and this liquid composite magnetic material contains solids (e.g., metal magnetic powder).

The composite magnetic material can then be supplied to a mold adjusted to a temperature of 100°C or higher, and then held for approximately 10 to 120 seconds before compression molding. This makes it easier for the composite magnetic material supplied to the mold to become liquid.

Furthermore, it is more preferable for this mold to be adjusted to a temperature of 140°C or less, as this makes it difficult for the thermosetting reaction of the thermosetting resin contained in the composite magnetic material to proceed before and during compression molding, and also further suppresses the volatilization of high-melting-point compounds.

The mixture is then compression-molded from both the top and bottom of the mold or from either the top or ^bottom using a movable punch (press head) or the like at a molding pressure of 1000 kgf/cm² or ^less (9.8 x ^{10³ N} /cm² or ^less ) to obtain a composite magnetic molded body. This molding pressure is preferably 800 kgf/cm² or ^less (7.84 x ^10³ N/ ^cm² or ^less ), and more preferably 500 kgf/cm² or less (4.9 x 10³ N/cm² or ^less ). It is also preferably ³ kgf/cm² or more (2.94 x 10³ N/cm² or more), and even more preferably ⁵ kgf/cm² or more (4.9 x 10³ N/ ^cm² or more). The compression molding time is not limited, but is preferably 5 seconds to 5 minutes.
It is more preferable to obtain a composite magnetic molded body by compression molding the liquid composite magnetic material while it is still in a fluid state using a molding pressure of 1000 kgf/cm2 or ^less from both the top and bottom of the mold or from either the top or bottom, so that the density becomes 5.45 g/ ^cm3 or more, more preferably 5.50 g/cm3 or ^more , because this makes it easier to obtain a composite magnetic molded body with a high density.

Here, "compression molding the liquid composite magnetic material so that the density is 5.45 g/cm ^or more while the composite magnetic material is in a fluid state" means that the composite magnetic material maintains its fluid state until the density of the composite magnetic material reaches 5.45 g/cm or ^more (for example, the melt viscosity of the composite magnetic material is 1300 Ps·s or less, or even 1100 Ps·s or less). In other words, compression molding is performed so that the density reaches 5.45 g/cm ^{or more} before the thermosetting reaction of the thermosetting resin contained in the composite magnetic material substantially progresses. Although this varies depending on the type of thermosetting resin contained in the composite magnetic material, as a guideline, in cases where an epoxy resin is included, for example, compression molding is preferably performed so that the density reaches 5.45 g/cm ^{or more} within 5 to 120 seconds, or even 5 to 90 seconds, from the start of compression molding.
After the density reaches 5.45 g/cm ³ or more, the composite magnetic material may be in a state where it does not have fluidity (a state where the thermosetting reaction of the contained thermosetting resin has substantially progressed).

[Thermosetting process]
The thermosetting process involves heat-treating the composite magnetic molded body obtained in the compression molding process to thermally cure the thermosetting resin while volatilizing and removing the high-melting-point compound contained in the composite magnetic molded body, thereby obtaining a composite magnetic thermosetting molded body. Specifically, the composite magnetic molded body after the compression molding process is heat-treated at a temperature equal to or higher than the recommended thermosetting temperature of the thermosetting resin contained therein to heat-cure it. The heat treatment temperature can be set appropriately depending on the type of thermosetting resin contained in the composite magnetic material, but examples include temperatures of 150°C to 330°C, and even 160°C to 310°C. The heat treatment time can also be, for example, 0.1 hours to 5 hours, or even 0.2 hours to 3 hours. This heat treatment can be performed in a mold, after removal from the mold, or both. The resulting composite magnetic thermosetting molded body can then be selectively subjected to processes such as surface polishing and coating, as needed.

In this thermosetting process, it is preferable to volatilize and remove the high-melting point compounds contained in the composite magnetic molded body, thereby obtaining a composite magnetic thermosetting molded body that is substantially free of high-melting point compounds (the content of high-melting point compounds is less than 0.1 wt%, or even less than 0.05 wt%). However, this is not limited to this, and a composite magnetic thermosetting molded body in which some of the high-melting point compounds contained in the composite magnetic molded body remain (for example, the content of high-melting point compounds is 0.1 wt% to 1.0 wt%, or even 0.5 wt% to 0.9 wt%) may also be obtained.

In this way, a composite magnetic thermosetting molded body composed of a metal magnetic powder and a thermosetting resin can be manufactured. The density of this composite magnetic thermosetting molded body can be 5.45 g/ ^cm3 or more, and even 5.50 g/ ^cm3 or more. The relative magnetic permeability of this composite magnetic thermosetting molded body can be 24.0 or more, and even 25.0 or more.

In the case where the aforementioned compression molding process involves embedding a coil in a composite magnetic material and compressing and molding it into one piece to obtain a composite magnetic molded body incorporating a coil, a coil component can be manufactured, for example, by the process shown in Figure 1, as a modified example of the method for manufacturing a composite magnetic thermosetting molded body according to this embodiment, although this is not limited thereto.

Specifically, an air-core coil 11 formed from a wire such as a round wire is first prepared (see FIG. 1A). This air-core coil 11 is composed of a winding section around which an insulating-coated wire is wound and a coil lead-out section 12 where the wire is drawn from the winding section. Next, a mold 21 including a lower punch of a press machine is adjusted to 100°C or higher. The air-core coil 11 is placed in the mold 21. Powdered composite magnetic material 22 prepared in the material preparation process described above is then introduced through the opening of the mold 21 to fill the coil winding section (including the inside of the loops of the wound wire and the gaps between the loops) and the spaces above and below the coil. However, the two coil lead-out sections 12 of the winding are exposed from the composite magnetic material 22 (see FIG. 1B). The composite magnetic material 22 and the air-core coil 11 are then compression-molded using the upper punch, which is also temperature-adjusted, at the molding pressure described above, to integrally compress and mold the composite magnetic material 22 and the air-core coil 11, yielding a coil-encapsulated composite magnetic molded body (see FIG. 1C). The coil-encapsulated composite magnetic molded body is then removed from the mold and heat-cured at a predetermined temperature, volatilizing and removing the high-melting-point compound. The air-core coil 11 is then embedded in the heat-cured composite magnetic thermosetting molded body 32 (magnetic outer casing and magnetic core material that becomes the magnetic core), and the two coil lead-out portions 12 are exposed to the outside and serve as terminals, resulting in a coil component (Figure 1(d)).

Instead of using an air-core coil, a coil assembly consisting of a coil and another magnetic core material that will serve as the magnetic core can be prepared and used to manufacture coil components using a method similar to that described above. In this case, the magnetic outer casing (outer core material) will be made of the composite magnetic thermosetting molded body described above, but the magnetic core (inner core material) will be made of a material different from the composite magnetic thermosetting molded body described above (such as a ferrite core). However, it is more preferable to use a coil component in which both the outer core material and inner core material are made of the composite magnetic thermosetting molded body described above.

The above describes the method for manufacturing a composite magnetic thermosetting molded body according to this embodiment, but the present invention is not limited to the above-described embodiment and also includes various modifications, improvements, etc. as long as the object of the present invention is achieved.
Furthermore, the above-described embodiments can be combined as appropriate without departing from the spirit of the present invention.

The following describes examples of the present invention, but the present invention is not limited to these examples, and as mentioned above, various modifications are possible within the technical concept of the present invention.

Example 1
A mixture of iron powder grades with an average particle size ( _D50 ) of approximately 25 μm and iron powder grades with an average particle size ( _D50 ) of approximately 2 μm was prepared as the metal magnetic powder used in the composite magnetic material, and a thermosetting epoxy resin (curing temperature 210°C) containing a curing agent was prepared as the thermosetting resin. Benzophenone (melting point 49°C, boiling point 305°C) was also prepared as the high-melting-point compound used in the composite magnetic material.

First, a predetermined amount of benzophenone was weighed out and mixed with methyl ethyl ketone (MEK). A predetermined amount of the epoxy resin was then mixed in and thoroughly dissolved to form a solution. A predetermined amount of the metal magnetic powder was then mixed into this solution and thoroughly stirred with a planetary mixer to produce a slurry. After granulating this slurry, the dilution solvent, methyl ethyl ketone (MEK), was dried to obtain a granulated powder of the composite magnetic material. The mass of the epoxy resin and the mass of the benzophenone were 3 wt% and 0.5 wt% (17 wt% of the epoxy resin) of the total mass of the granulated powder of the composite magnetic material, respectively.

A control granulated powder of composite magnetic material was also prepared in the same manner as above, except that benzophenone was not added. The mass of epoxy resin in the control granulated powder of composite magnetic material was 3 wt % of the total mass.

Next, the temperature of the die, including the lower punch, of a temperature-controllable press machine equipped with an air cylinder was adjusted to 100°C or higher and 140°C or lower. Once the die temperature stabilized, one of the granulated powders of the composite magnetic material described above was fed into the die and held there for 30 seconds until its temperature was approximately the same as the die temperature. After 30 seconds, an upper punch, also held at the same temperature, was inserted, and a molding pressure of 100 kgf/ ^cm2 (9.8 x ¹⁰² N/ ^cm2 ) was applied to the upper punch to perform compression molding. After each compaction, the resulting composite magnetic molded body was removed from the die. The composite magnetic molded body removed from the die was then heat-treated at 200°C for 2 hours to thermally cure (aftercure) the thermosetting resin, yielding two types of disc-shaped composite magnetic thermosetting molded bodies.
All of the granulated powders had good powder fluidity when fed into the mold. The composite magnetic material containing benzophenone was in a fluid liquid state at the start of compression molding and until it reached a predetermined density ( ^5.45 g/cm or higher).

This disk-shaped composite magnetic thermosetting molded body was used to evaluate the density of the resulting composite magnetic thermosetting molded body. A toroidal-shaped composite magnetic thermosetting molded body was also created by drilling a hole in the center of this disk-shaped composite magnetic thermosetting molded body, and this toroidal-shaped composite magnetic thermosetting molded body was used to evaluate the relative magnetic permeability of the resulting composite magnetic thermosetting molded body.

Specific evaluation methods included calculating density from the measured outer diameter, height, and mass of the disk-shaped composite magnetic thermosetting molded body. For relative permeability, 20 turns of insulating-coated copper wire (enameled wire) were wound around the toroidal composite magnetic thermosetting molded body, and the inductance value was measured using an LCR meter (Agilent E4980A LCR Meter). The core multiplier was calculated from the outer diameter, inner diameter, and thickness of the toroidal composite magnetic thermosetting molded body, and the relative permeability was calculated from the inductance value.

As a result, the composite magnetic thermosetting molded body produced using the composite magnetic material containing benzophenone had a density of 5.62 g/cm ³ and a relative magnetic permeability of 26.2, while the composite magnetic thermosetting molded body produced using the control composite magnetic material (composite magnetic material not containing benzophenone) had a density of 5.37 g/cm ³ and a relative magnetic permeability of 23.2. In other words, it was made clear that by using a composite magnetic material containing a high-melting point compound, a composite magnetic thermosetting molded body with high density and high relative magnetic permeability can be obtained at a low molding pressure.

Furthermore, the properties of the granulated powder of the composite magnetic material containing benzophenone prepared above and the granulated powder of the control composite magnetic material were confirmed and photographed at room temperature (20±5°C) and 100°C. These photographs are shown in Figure 2. As a result, because benzophenone, a high-melting-point compound, is solid at room temperature (20±5°C), the granulated powder of the composite magnetic material containing benzophenone had good powder fluidity when fed into the mold, as shown in the photograph in the lower left of Figure 2, similar to the granulated powder of the control composite magnetic material (upper left of Figure 2). However, because benzophenone liquefies at 100°C, the granulated powder of the composite magnetic material containing benzophenone became liquid during thermoforming (lower right of Figure 2), demonstrating different properties from the granulated powder of the control composite magnetic material, which remained powdery even during thermoforming (upper right of Figure 2).

Example 2
The same metal magnetic powder and thermosetting resin used in the composite magnetic material were prepared as in Example 1. In addition, 12 types of compounds shown in Table 1 below were prepared as high-melting point compounds used in the composite magnetic material.

Twelve types of granulated powder of composite magnetic material were prepared in the same manner as in Example 1 (No. 7 in Table 1 below is the same as that prepared in Example 1). The mass of the epoxy resin and the mass of the high-melting-point compound were 3 wt % and 0.5 wt %, respectively, of the total mass of the granulated powder of the composite magnetic material (17 wt % relative to the mass of the epoxy resin). Furthermore, composite magnetic thermosetting molded bodies were prepared in the same manner as in Example 1, and evaluated on a three-point scale for the fluidity when the granulated powder was supplied to the mold (powder supply fluidity) and whether a high-density molded body could be produced even at a low molding pressure of 1000 kgf/cm ² or less (low molding pressure effect). Furthermore, whether the high-melting-point compound contained in the granulated powder of the composite magnetic material remained during the granulated powder preparation process and after storage at 40°C for 24 hours (storability) was also evaluated on a three-point scale. A comprehensive evaluation was also conducted based on the evaluation of these three items. The results are also shown in Table 1 below. The specific evaluation criteria for each item are as follows:

<Fluidity during feeding>
◎: No change in fluidity 〇: Fluidity changes but powder can be fed ×: Fluidity deteriorates <Effect of low molding pressure>
◎: Density changes at low molding pressure (>10%)
○: Density changes at low molding pressure (≦10%)
×: No change in density at low molding pressure <Storage>
◎: No change in weight during storage. 〇: Weight changes during storage. ×: Evaporation progresses during handling. <Overall evaluation>
◎: All of the above items are rated as ◎. ○: All of the above items are rated as ○ or higher. ×: One or more of the above items are rated as ×.

These results show that in order for a composite magnetic material to have the fluidity of a powder when fed into a mold, the high-melting-point compound contained therein must be solid at room temperature, i.e., have a melting point of 25°C or higher. Furthermore, to ensure the shelf life of a composite magnetic material at 40°C or below (e.g., 10°C to 40°C), the high-melting-point compound contained therein must be virtually non-volatile in this temperature range, i.e., have a boiling point of 160°C or higher. Furthermore, in order to perform thermal molding at 100°C or above (e.g., 100°C to 140°C), the melting point of the high-melting-point compound contained in the composite magnetic material must be below 100°C.

Example 3
The same metal magnetic powder and thermosetting resin used in the composite magnetic material were prepared as in Example 1. Coumarin (melting point 73°C, boiling point 298°C) was also prepared as the high-melting-point compound used in the composite magnetic material.

Nine types of granulated powder of composite magnetic material were then prepared in the same manner as in Example 1, except that the blending amounts were as shown in Table 2 below (No. 25 in Table 2 below is the same as No. 12 in Example 2). Furthermore, composite magnetic thermosetting molded bodies were prepared using the same method as in Example 1, and evaluated on a three-point scale for powder feeding fluidity and low molding pressure effect using the same criteria as in Example 2. Also, as in Example 2, an overall evaluation was made on a three-point scale based on the evaluation of these two items. The results are also shown in Table 2 below.

These results show that the mass ratio of the high-melting-point compound in the composite magnetic material is preferably 3 wt% or more and 100 wt% or less relative to the mass of the thermosetting resin, and particularly preferably 10 wt% or more and 33 wt% or less.

The present embodiment encompasses the following technical ideas.
(1) A method for producing a composite magnetic thermosetting molded body, the method including a material preparation step, a compression molding step, and a thermosetting step, in which the material preparation step is a step of mixing a metal magnetic powder, a thermosetting resin, and a high-melting-point compound having a melting point of 25°C or more but less than 100°C and a boiling point of 150°C or more so that the mass of the high-melting-point compound is 3.0 wt% or more and 100 wt% or less relative to the mass of the thermosetting resin to obtain a powdered composite magnetic material, the compression molding step is a step of supplying the composite magnetic material to a mold adjusted to 100°C or more to make it liquid, and compression molding it at a molding pressure of ¹⁰⁰⁰ kgf/cm2 or less to obtain a composite magnetic molded body, and the thermosetting step is a step of heat-treating the composite magnetic molded body to thermally cure the thermosetting resin while volatilizing and removing the high-melting-point compound, thereby obtaining the composite magnetic thermosetting molded body.
(2) A method for producing a composite magnetic thermosetting molded body as described in ⁽¹ ), wherein in the compression molding process, the composite magnetic material is compression molded at a molding pressure of 1000 kgf/cm2 or less so that the density of the liquid composite magnetic material is 5.45 g/cm3 or ^more while it is in a fluid state.
(3) A method for producing a composite magnetic thermosetting molded body according to (1) or (2), wherein the high-melting point compound in the material preparation step has a melting point of 80°C or less and a boiling point of 330°C or less.
(4) In the compression molding process, the composite magnetic material is supplied to the mold adjusted to a temperature of 100°C or higher and 140°C or lower. A method for manufacturing a composite magnetic thermosetting molded body according to any one of (1) to (3).
(5) The method for manufacturing a composite magnetic thermosetting molded body described in any one of (1) to (4), wherein the compression molding process is a process of encapsulating a coil in the composite magnetic material and compressing and molding the composite magnetic material to obtain the composite magnetic molded body encapsulating the coil.

11 Air-core coil 12 Coil lead-out portion 21 Mold 22 Composite magnetic material 32 Composite magnetic thermosetting molded body

Claims (5)

A method for manufacturing a composite magnetic thermosetting molded body, comprising a material preparation step, a compression molding step, and a thermosetting step,
the material preparation step is a step of obtaining a powdery composite magnetic material by mixing a metal magnetic powder, a thermosetting resin, and one or more high-melting-point compounds having a melting point of 25°C or more but less than 100°C and a boiling point of 160°C or more, which are selected from the group consisting of cyclohexanol, p-cresol, phenol, L-menthol, benzophenone, α,α'-dichloro-o-xylene, stearyl alcohol, 3,5-dimethylphenol, butylhydroxytoluene, and coumarin, in an ambient temperature of room temperature such that the mass of the high-melting-point compound is 3.0 wt% or more and 100 wt% or less relative to the mass of the thermosetting resin;
the compression molding step is a step of supplying the composite magnetic material to a mold adjusted to 100°C or higher to make it liquid, and compression molding it under a molding pressure of 1000 kgf/cm2 or ^less to obtain a composite magnetic molded body,
The thermosetting step is a step of heat-treating the composite magnetic molded body, and thermally curing the thermosetting resin while volatilizing and removing the high-melting point compound, to obtain the composite magnetic thermosetting molded body.
A method for manufacturing a composite magnetic thermosetting molded body. 2. The method for producing a composite magnetic thermosetting molded body according to claim ¹ , wherein in the compression molding step, compression molding is performed at a molding pressure of 1000 kgf/cm2 or less so that the density of the liquid composite magnetic material becomes 5.45 g/ ^cm3 or more while the liquid composite magnetic material is in a fluid state. The method for manufacturing a composite magnetic thermosetting molded body according to claim 1 or 2, wherein the material preparation process is a process in which the high-melting-point compound is one or more selected from the group consisting of benzophenone, α,α'-dichloro-o-xylene, stearyl alcohol, 3,5-dimethylphenol, butylhydroxytoluene, and coumarin, and the high-melting-point compound is mixed with the thermosetting resin in an ambient temperature environment so that the mass of the high-melting-point compound is 10 wt% or more and 33 wt% or less relative to the mass of the thermosetting resin. The method for manufacturing a composite magnetic thermosetting molded body according to any one of claims 1 to 3, wherein in the compression molding process, the composite magnetic material is supplied to the mold, the temperature of which is adjusted to 100°C or higher and 140°C or lower. A method for manufacturing a composite magnetic thermosetting molded body according to any one of claims 1 to 4, wherein the compression molding process is a process of incorporating a coil into the composite magnetic material and compressing and molding it into an integral body to obtain the composite magnetic molded body incorporating the coil.