JP7632002B2 - Manufacturing method for coil components using composite magnetic material - Google Patents

Description

The present invention relates to a method for manufacturing coil components using composite magnetic materials.

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

JP 2006-319020 A

When using such a composite magnetic material to manufacture a coil part containing a coil by compression molding using a mold, the wiring groove of the upper or lower mold in which the coil draw-out part (the wire that becomes the coil draw-out line of the coil part) is placed is usually designed so that the clearance between this coil draw-out part and the wiring groove of the upper or lower mold of the mold is extremely small. Furthermore, this mold is designed so that there is almost no clearance in other parts during molding. When using such a mold to perform thermal molding of a composite magnetic material with an embedded coil (heating the mold to perform compression molding), if further pressure is applied after the composite magnetic material is sufficiently filled in the mold, the clearance between the coil draw-out part and the wiring groove is large enough that most of the metal magnetic powder contained in the composite magnetic material cannot pass through, so the thermosetting resin in the composite magnetic material separates and flows into this clearance and is discharged, which may result in a decrease in the content of thermosetting resin in the resulting molded body (coil part).

The resulting molded body (coil component) has a reduced content of the resin component that insulates the metal magnetic powder particles, which are electrical conductors, so the insulating layer of the resin component between the metal magnetic powder particles becomes extremely thin, and the metal magnetic powder particles come into electrical contact with each other, resulting in a low breakdown voltage when a direct current voltage is applied (for example, 50 V/mm or less). In particular, when a composite magnetic material containing a thermosetting resin with a low melt viscosity is used, the metal magnetic powder and the thermosetting resin tend to separate during thermal molding, making the above problem more likely to occur.

The present invention has been made in consideration of the above problems, and aims to provide a method for manufacturing coil components in which separation of the metal magnetic powder and thermosetting resin in the composite magnetic material in which the coil is embedded during thermal molding is unlikely to occur, and in which the breakdown voltage of the resulting coil components is unlikely to decrease when a direct current voltage is applied.

The inventors conducted extensive research to solve the above problems, and discovered that by using a mold having a discharge hole with a specified hole diameter and opening area for heat molding, separation of the metal magnetic powder and thermosetting resin in the composite magnetic material in which the coil is embedded during heat molding is unlikely to occur, and the breakdown voltage of the resulting coil component is unlikely to decrease when a direct current voltage is applied, leading to the completion of the present invention.

That is, the present invention is a manufacturing method for a coil component in which a composite magnetic material composed of a metal magnetic powder and a thermosetting resin is molded and thermoset into a composite magnetic thermosetting molded body, and a coil winding portion is contained in the composite magnetic thermosetting molded body, and the pull-out portion of the coil protrudes from the composite magnetic thermosetting molded body, the manufacturing method being provided with an upper mold and a lower mold, and a wiring groove in which the pull-out portion of the coil is disposed in an area of the upper mold that is brought into contact with the lower mold or an area of the lower mold that is brought into contact with the upper mold, and further, in a state in which the coil pull-out portion is disposed in the wiring groove and the upper mold and the lower mold are brought into contact with each other, the hole diameter is such that the metal magnetic powder can pass through and the total opening area is greater than the coil portion This method of manufacturing a coil part includes a compression molding process in which a mold is prepared with one or more discharge holes that are 0.003% to 1.5% of the surface area of the product, the coil windings are placed inside the mold, the coil pull-out parts are placed in wiring grooves so that the coil pull-out parts protrude from the inside of the mold, a composite magnetic material is filled inside the mold so as to embed the coil windings, the mold is heated, and the composite magnetic material is compression molded while flowing out from the discharge holes to obtain a composite magnetic molded body containing the coil windings, and a heat curing process in which the composite magnetic molded body is heat-treated to heat-set it, thereby obtaining a coil part.

The present invention provides a method for manufacturing coil components in which separation between the metal magnetic powder and the thermosetting resin in the composite magnetic material in which the coil is embedded during thermal molding is unlikely to occur, and the dielectric breakdown voltage of the resulting coil components is unlikely to decrease when a DC voltage is applied to them.

1 is a perspective view of a state in which a coil is placed inside a lower die of a mold used in a manufacturing method of a coil component according to this embodiment, and a lead-out portion of the coil is placed in a wiring groove. FIG. 2 is a perspective view of the lower and upper dies of the mold of FIG. 1 in contact with each other; FIG. 13 is an enlarged perspective view of the vicinity of the wiring groove in a state in which a lead-out portion of a coil is disposed in the wiring groove of a modified example of a mold used in the manufacturing method of a coil component according to the present embodiment. FIG. 1 is a perspective view of a state in which a coil is placed inside a lower die of a mold used in a conventional method for manufacturing a coil component, and a lead-out portion of the coil is placed in a wiring groove.

The following describes an embodiment of the present invention.

In the method for manufacturing a coil component according to this embodiment, a coil component is manufactured using a composite magnetic material made of a metal magnetic powder and a thermosetting resin, and a coil having a winding portion and an extraction portion.
First, each material will be described.

<Composite magnetic materials>
The composite magnetic material used in the manufacturing method of the coil component according to the present embodiment is a material composed of a metal magnetic powder and a thermosetting resin, that is, a material that contains at least a metal magnetic powder and a thermosetting resin, and these are the main components (a total of 90 wt % or more).
In addition, composite magnetic materials containing other components (for example, dispersants, plasticizers, lubricants, etc.) besides the above are not excluded as long as they do not affect the effects of the present invention.

The content of the metal magnetic powder in the composite magnetic material is preferably 95 wt% or more, more preferably 96 wt% or more. The upper limit is preferably 98.5 wt% or less, more preferably 98 wt% or less. The content of the thermosetting resin is preferably 1.5 wt% or more, more preferably 2.0 wt% or more. The upper limit is preferably 5.0 wt% or less, more preferably 4.0 wt% or less. Furthermore, from the viewpoint of ease of filling into a mold, this composite magnetic material is preferably a granulated powder.
The metallic magnetic powder and the thermosetting resin that constitute this composite magnetic material will be described in detail below.

(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. As the metal magnetic material, for example, iron or an alloy containing iron (iron-silicon, iron-aluminum-silicon alloy, iron-nickel alloy, etc.) can be used. However, these are merely examples, and other metal magnetic materials may be used. In addition, 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.

In particular, from the viewpoint of magnetic properties and availability, it is more preferable to use a metal magnetic powder containing iron as the main component and chromium (Cr), silicon (Si), nickel (Ni), aluminum (Al), cobalt (Co), carbon (C), boron (B), etc. as secondary components. 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), non-crystalline metal powders such as Fe-Si-Cr-B amorphous powder, and crystalline iron powders such as carbonyl iron powder. Of the above materials, it is more preferable to use materials that can be made into roughly spherical metal magnetic powder (such as Fe-Si-Cr-B amorphous powder or Fe-Si-Cr alloy powder). This is because it makes it easier to compress and mold composite magnetic materials that contain this metal magnetic powder.

The content of iron, which is the main component of the metal magnetic powder, is preferably 85 wt% or more, and more preferably 86 wt% or more. It is also preferably 98 wt% or less, and more preferably 97 wt% or less. It is also preferable that the powder contains one or more of the above-mentioned minor components, with the remainder being iron and unavoidable impurities.

Furthermore, the chromium content of this metal magnetic powder is preferably 2 wt % or more and 10 wt % or less, and more preferably 2.5 wt % or more and 8 wt % or less.
Chromium easily combines with oxygen in the air to produce a chemically stable oxide (e.g., _Cr2O3 , _etc. ). Therefore, a composite magnetic thermosetting molded body containing chromium has particularly excellent corrosion resistance. Furthermore, since chromium oxide has a high specific resistance, a chromium oxide layer is formed near the surface of the particles constituting the composite magnetic thermosetting molded body of the coil component obtained by the manufacturing method of the coil component according to this embodiment, which makes it easier to insulate between the particles.
Therefore, by setting the chromium content within the above range, it is possible to obtain a metal magnetic powder that can constitute a composite magnetic material that has excellent corrosion resistance and can be used to manufacture coil components with smaller eddy current loss.

For the same reason, the metal magnetic powder preferably has a nickel content of 2 wt% or more and 10 wt% or less, and more preferably 2.5 wt% or more and 8 wt% or less. Similarly, the metal magnetic powder preferably has an aluminum content of 2 wt% or more and 10 wt% or less, and more preferably 2.5 wt% or more and 8 wt% or less.

Furthermore, the metal magnetic powder preferably has a silicon content of 2 wt % or more and 10 wt % or less, and more preferably 3 wt % or more and 8 wt % or less.
Silicon is a component that can increase the relative magnetic permeability of the coil component obtained. Silicon is also a component that can suppress interparticle eddy current loss because the resistivity of the metal magnetic powder increases when the metal magnetic powder contains silicon. Therefore, by setting the silicon content within the above range, a metal magnetic powder that can constitute a composite magnetic material that can produce coil components with high relative magnetic permeability and low eddy current loss can be obtained.

This metal magnetic powder may 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, the material 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 this metal magnetic powder is preferably 2 μm to 40 μm, more preferably 4 μm to 30 μm. Furthermore, the particle shape of the metal magnetic powder is preferably approximately spherical (for example, an approximately spherical shape in which the value obtained by dividing the major axis by the minor axis is 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.

The maximum particle size of this metal magnetic powder is preferably 75 μm or less, more preferably 70 μm or less, even more preferably 60 μm or less, and even more preferably 50 μm or less.

Here, the above-mentioned "average particle size ( _D50 )" and "maximum particle size" refer to the powder size (median size) at an integrated value of 50% in the volumetric particle size distribution, and the maximum particle size, 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 particle size of the aggregate is meant. A specific example of a measuring device for these is the laser diffraction/scattering type particle size distribution measuring device (particle size distribution) LA-960 (manufactured by HORIBA Seisakusho).

In addition, it is preferable to use, as the metallic magnetic powder, a metallic magnetic material powdered by water atomization or gas atomization.
Here, the "water atomization method" refers to a method for producing metal powder by colliding molten metal with water (atomized water) sprayed at high speed to pulverize the molten metal and cool it.
The "gas atomization method" is a method in which a jet stream of inert gas or air is blown onto a flow of molten metal from the surrounding area to pulverize the flow of molten metal, solidify it, and turn it into metal powder.

The metal magnetic powder produced by the water atomization method or the gas atomization method has a substantially spherical shape (close to a sphere), so when manufacturing coil components using a composite magnetic material containing this metal magnetic powder, the filling rate can be easily increased. Also, as mentioned above, it becomes easier to compression mold the composite magnetic material containing this metal magnetic powder.

Furthermore, this metal magnetic powder may be one that has been subjected to a drying process to remove water adsorbed on the powder surface, i.e., a metal magnetic dry powder obtained by drying the powder. Examples of the powder drying process 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.

In addition, the metal magnetic powder may be surface-treated with a silane- or titanium-based coupling agent to improve wettability with the thermosetting resin, that is, a surface-treated metal magnetic powder obtained by surface-treating the powder with a silane- or titanium-based coupling agent. As the silane- or titanium-based coupling agent, it is more preferable to use a silane- or titanium-based coupling agent having an epoxy group, an amino group, or an isocyanate group as a functional group, from the viewpoint of affinity with the thermosetting resin described later. Examples of the surface treatment method for the powder include a dry treatment method in which a solution containing a coupling agent is dropped or sprayed onto the powder while stirring it with a mixer or the like, and a wet treatment method in which a solvent is added to the powder to make a slurry, a solution containing a coupling agent is added to the slurry, and the slurry is stirred, filtered, and dried. This surface treatment may be performed in combination with the drying treatment described above.

(Thermosetting resin)
The thermosetting resin is a reactive resin composition mainly composed of a prepolymer having a functional group, which is softened and flowed by heating, and gradually hardens by a crosslinking reaction that forms a three-dimensional network structure. The composite magnetic thermosetting molded body of the coil component obtained by the manufacturing method of the coil component according to the present embodiment contains a thermosetting resin composition, but in the present invention, this thermosetting resin composition may also be referred to as a "thermosetting resin". The thermosetting resin is not particularly limited as long as it plays a role as a binder resin and can be hardened by heating (for example, a resin used in a sealing material for semiconductors), and thermosetting epoxy resins (bisphenol type, naphthalene type, novolac type, aliphatic type, glycidylamine type, etc.), silicon resins (methylphenyl silicon resins, etc.), phenol resins (novolac type, resol type, etc.), polyamide resins, polyimide resins, melamine resins, polyphenylene sulfide resins, etc. may be used. A mixture of two or more types of thermosetting resins may also be used. In particular, from the viewpoint of heat resistance, it is more preferable to use an epoxy resin, and it is even more preferable to use a novolac type epoxy resin.
In addition, the manufacturing method of the coil component according to this embodiment is characterized in that, by using a mold described later, separation of the metal magnetic powder and the thermosetting resin in the composite magnetic material is unlikely to occur during thermal molding, even when a composite magnetic material containing a thermosetting resin with a low melt viscosity is used.

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

When preparing the composite magnetic material, a solvent may be mixed with the thermosetting resin to make the thermosetting resin into a resin solution. This solvent is removed by drying or the like in each process described below, but from the viewpoint of ease of removal, it is preferable to use a small amount of solvent (for example, the ratio of the volume of the solvent to the total volume of the 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 the like in each process described below, and suitable examples include organic solvents such as alcohol, toluene, chloroform, methyl ethyl ketone, acetone, and ethyl acetate.

<Coil>
The coil used in the manufacturing method of the coil component according to the present embodiment is formed by winding a wire such as a round wire or a flat wire. The shape, number, and number of turns of the wire are not particularly limited. The surface of the wire may be coated with an insulating material. The wire may be made of a metal material such as copper, and the diameter of the wire is not limited.

The coil comprises a winding section 101 around which the wire is wound, and a pull-out section 103 from which the wire is pulled out from the winding section. The pull-out section 103 serves as the coil pull-out wire of the coil component. Furthermore, the winding section 101 may have a core section that serves as a magnetic core material inside. Alternatively, the winding section 101 may be an air-core coil that does not have a core section inside.

<Manufacturing method of coil components>
Next, each step of the method for manufacturing the coil component according to this embodiment using the above-mentioned materials will be described in detail.

The manufacturing method of the coil component according to this embodiment includes at least the compression molding process and the heat curing process described below. Note that other processes (e.g., a material preparation process, a polishing process after heat curing, etc.) may be included as desired within the scope that does not affect the effects of the present invention.

[Compression molding process]
First, in this compression molding process, a predetermined mold is prepared. Specifically, a mold is prepared that includes an upper mold 11 and a lower mold 21, and has a wiring groove 33 along which a coil lead-out portion 103 can be arranged in an area of the upper mold 11 that comes into contact with the lower mold 21 or an area of the lower mold 21 that comes into contact with the upper mold 11, and further has one or more discharge holes 35 that have a hole diameter that allows the metal magnetic powder to pass through and a total opening area that is 0.003% to 1.5% of the surface area of the coil component when the coil lead-out portion 103 is arranged in the wiring groove 33 and the upper mold 11 and the lower mold 21 are in contact with each other. This discharge hole 35 is capable of passing the metal magnetic powder in the composite magnetic material together with the thermosetting resin during thermoforming in which the die is heated and compression molded, and for example, the minimum hole diameter may be 3 to 70 times, further 5 to 50 times, or further 5 to 20 times the average particle diameter ( _D50 ) of the metal magnetic powder. Furthermore, since this discharge hole 35 has the above-mentioned total opening area, the outflow amount of the composite magnetic material during thermoforming is prevented from becoming excessively large.

In particular, it is preferable that the minimum hole diameter of the discharge hole 35 of this mold is equal to or larger than the maximum particle diameter of the metal magnetic powder. Furthermore, it is even more preferable that the minimum hole diameter is larger than the maximum particle diameter of the metal magnetic powder. This is because it is easier to pass the composite magnetic material through the discharge hole 35 in a homogeneous state during thermal molding.

Here, the "hole diameter" of the discharge hole 35 refers to the diameter of the maximum inscribed circle in a cross section perpendicular to the hole of the discharge hole 35 (a cross section perpendicular to the penetrating direction of the discharge hole 35). Moreover, the "minimum hole diameter" of the discharge hole 35 refers to the smallest diameter among the diameters of the maximum inscribed circles in all cross sections perpendicular to the hole of the discharge hole 35. Therefore, when the minimum hole diameter of the discharge hole 35 is equal to or larger than the maximum particle diameter of the metal magnetic powder, all of the metal magnetic powder contained in the composite magnetic material can pass through together with the thermosetting resin.
The opening area of the discharge hole 35 is the area of the opening of the discharge hole 35 on the inner space side of the mold, and the "total opening area" is the sum of these opening areas (the opening area of the discharge hole 35 when there is only one discharge hole 35). Furthermore, the "surface area of the coil component" is the surface area of the composite magnetic thermosetting molded body obtained after the compression molding process and the thermosetting process (the same as the surface area of the inner space of the mold in a sufficiently compressed state), and does not include the surface area of the lead-out portion 103 of the coil (the surface area of the wire line).

The lower limit of the total opening area of the discharge holes 35 is preferably 0.005% or more of the surface area of the coil component, more preferably 0.007% or more, and even more preferably 0.01% or more, since this makes it easier to flow out of the composite magnetic material from the discharge holes 35 during thermal molding. The upper limit is more preferably 1.4% or less of the surface area of the coil component, and even more preferably 1.3% or less, since this makes it easier to increase the density of the resulting coil component.

The minimum hole diameter of the discharge hole 35 is not limited, but may be 50 μm or more, 60 μm or more, 70 μm or more, or 75 μm or more. The upper limit is also not limited, but may be 2000 μm or less, 1500 μm or less, or 1000 μm or less.

The discharge hole 35 is preferably formed by a discharge groove 31 provided in the area of the upper die 11 that contacts the lower die 21 or the area of the lower die 21 that contacts the upper die 11. In other words, the above-mentioned mold has a discharge groove 31 in the area of the upper die 11 that contacts the lower die 21 or the area of the lower die 21 that contacts the upper die 11, and it is preferable that this discharge groove 31 forms the above-mentioned discharge hole 35 when the upper die 11 and the lower die 21 are brought into contact. This is because, during thermoforming, the composite magnetic material can be easily discharged by the discharge hole 35 provided in the area of contact between the upper die 11 and the lower die 21 (area adjacent to the contact surface), and the mold is also easy to design and manufacture.

1 and 2, a mold may be exemplified in which a plurality of discharge grooves 31 are provided in both the region of the upper mold 11 that contacts the lower mold 21 and the region of the lower mold 21 that contacts the upper mold 11, and when the upper mold 11 and the lower mold 21 are brought into contact with each other, one discharge groove 31 of the upper mold 11 and one discharge groove 31 of the lower mold 21 are combined to form one discharge hole 35. Also, the mold may have discharge grooves 31 only in the region of the upper mold 11 that contacts the lower mold 21, or only in the region of the lower mold 21 that contacts the upper mold 11. Furthermore, all discharge holes 35 of the mold may be formed by the discharge grooves 31.
However, this does not exclude the use of a mold having discharge holes 35 in areas other than the contact area between the upper mold 11 and the lower mold 21 (for example, the side surfaces or top surface of the upper mold of the mold, or the side surfaces of the lower mold).

In addition, when the mold has a configuration having multiple side peripheral surfaces, it is preferable that, among the multiple side peripheral surfaces, the pull-out portion protruding surface from which the pull-out portion 103 of the coil protrudes and the discharge hole opening surface from which the discharge hole 35 opens are configured differently, as in the embodiment shown in Figures 1 and 2, for example. This is because, when polishing the surface of the coil part obtained after the compression molding process and the thermosetting process, it is easy to polish the protrusion of the composite magnetic thermosetting molded body formed from the composite magnetic material that has flowed out from the discharge hole 35.

Alternatively, as a modified example, the discharge groove 31 may be configured to be integrated with the wiring groove 33 as in the embodiment shown in FIG. 3. In other words, the clearance generated when the coil pull-out portion 103 is placed in the wiring groove 33 and the upper mold 11 and the lower mold 21 are abutted against each other may be the discharge hole 35. In this case, the clearance may be a hole diameter through which the metal magnetic powder can pass, and the total opening area of the discharge hole 35 including the opening area of the clearance may be 0.003% to 1.5% of the surface area of the coil component. In the embodiment shown in FIG. 3, the wiring groove 33 (discharge groove 31) is configured so that the discharge holes 35 (two discharge holes 35 sandwiching the coil pull-out portion 103) are formed on both sides of the coil pull-out portion 103, but the wiring groove 33 (discharge groove 31) may be configured so that the discharge hole 35 is formed only on one side of the coil pull-out portion 103.
However, if this exhaust groove 31 is provided separately from the wiring groove 33 (the exhaust groove 31 and the wiring groove 33 are separate), the exhaust hole 35 will be formed in a region separate from the wiring groove 33, which is preferable because it makes it easier for the pull-out portion 103 of the coil arranged in the wiring groove 33 to be stable during molding.

The wiring groove 33 may have any configuration that allows the coil pull-out portion 103 to be placed. In particular, it is preferable that the spacing between the inner surface of the wiring groove 33 and the coil pull-out portion 103 when the coil pull-out portion 103 is placed is less than the maximum particle diameter of the metal magnetic powder. A mold having such wiring grooves 33 in both the area where the upper mold 11 contacts the lower mold 21 and the area where the lower mold 21 contacts the upper mold 11 (for example, a mold having a configuration in which these can be combined) may be used, or a mold having wiring grooves 33 only in the area where the upper mold 11 contacts the lower mold 21 or only in the area where the lower mold 21 contacts the upper mold 11 may be used. A mold having two or more wiring grooves may also be used.

As for the number of discharge holes 35 mentioned above, it is preferable for the mold to have two or more discharge holes 35, since this makes it easier for the composite magnetic material to flow out of the discharge holes 35 during thermal molding. In particular, it is very preferable for the mold to have two or more discharge holes 35 in the contact area between the upper mold 11 and the lower mold 21, as shown in Figure 2.

Next, the winding portion 101 of the coil (e.g., an air-core coil) is placed inside the prepared mold. Then, as shown in Figures 1 and 2, the pull-out portion 103 of the coil is placed in the wiring groove 33 so that the pull-out portion 103 of the coil protrudes from inside the mold. Furthermore, using an injector or the like, the composite magnetic material is filled into the inside of the mold so as to embed the winding portion 101 of the coil (so as to embed the upper and lower spaces, side spaces, and internal space of the winding portion 101). Note that when the composite magnetic material is poured into the mold, the mold may be vibrated while being poured in, in order to prevent the occurrence of areas inside the mold that are not sufficiently filled with the composite magnetic material.

Then, the mold is heated to adjust the temperature, and pressure is applied from both above and below or either one side with a punch or the like to cause the composite magnetic material to flow out of the discharge hole 35 while compression molding is performed to obtain a composite magnetic molded body containing the coil winding part 101. The mold may be heated before filling with the composite magnetic material. In this thermal molding, as described above, a part of the composite magnetic material flows out of the discharge hole 35 by pressure after the composite magnetic material is sufficiently filled in the mold, but since this discharge hole 35 is large enough that the metal magnetic powder and the thermosetting resin can pass through in a homogeneous mixture, separation of the metal magnetic powder and the thermosetting resin in the composite magnetic material embedding the coil is unlikely to occur. Therefore, the composite magnetic molded body obtained by this compression molding process has a composition (content of thermosetting resin) that is substantially unchanged from the composite magnetic material before molding.

For example, when a conventional mold without a discharge hole 35 as shown in FIG. 4 is used, the clearance between the wiring groove 33 and the coil pull-out portion 103 is extremely small, and there is almost no clearance in other parts, so that during thermoforming, there is a high possibility that the thermosetting resin in the composite magnetic material will separate and flow into the clearance between the wiring groove 33 and the coil pull-out portion 103. This will result in a decrease in the content of thermosetting resin in the obtained composite magnetic thermosetting molded body. This may lead to a decrease in the breakdown voltage, etc. On the other hand, if the molding pressure is lowered to prevent such separation of the thermosetting resin, it may be difficult to obtain a molded body (coil part) with a high density.
However, since the mold used in the manufacturing method of the coil component according to the present embodiment has the above-mentioned discharge hole 35, separation of the metal magnetic powder in the composite magnetic material embedding the coil from the thermosetting resin is unlikely to occur during thermal molding, and the resulting coil component is characterized in that a decrease in the breakdown voltage is unlikely to occur when a DC voltage is applied to the resulting coil component. Furthermore, it is possible to prevent the composite magnetic material from flowing out more than necessary during this thermal molding, making it easy to obtain a high-density molded body (coil component).

In this compression molding step, it is preferable to heat the mold to 100°C or higher and 180°C or lower, and perform compression molding at a molding pressure of ³ kgf/cm2 or ^higher and 5000 kgf/cm2 or lower (2.94 x 10 N/ ^cm2 or higher and 4.9 x ¹⁰⁴ N/ ^cm2 or lower) for a time period of 10 seconds to 5 minutes. In the manufacturing method for coil components according to this embodiment, the compression molding step is performed using the mold as described above, so that even under the molding pressure conditions as described above, the composite magnetic material can be discharged from the discharge hole 35 and a molded body (coil component) with high density can be obtained. Furthermore, when a DC voltage is applied to the obtained molded body (coil component), a decrease in the dielectric breakdown voltage is unlikely to occur.

Instead of using an air-core coil, a coil assembly consisting of a coil and a magnetic core material that serves as the magnetic core may be prepared, and this may be used to perform thermoforming in a manner similar to that described above. In this case, the magnetic exterior body (outer core material) of the resulting coil component will be composed of a composite magnetic thermosetting molded body, but the magnetic core (inner core material) will be composed of a material (such as a ferrite core) different from this composite magnetic thermosetting molded body. However, it is more preferable to use a coil component in which both the outer core material and the inner core material are composed of this composite magnetic thermosetting molded body.

[Thermal curing process]
The heat curing process is a process in which the composite magnetic molded body containing the coil winding portion 101 obtained in the compression molding process is heat-treated and heat-cured to obtain a coil component in which the coil winding portion 101 is contained in the composite magnetic thermosetting molded body. Specifically, the composite magnetic molded body containing the coil winding portion 101 after the compression molding process is heat-treated at a temperature equal to or higher than the recommended heat curing temperature of the thermosetting resin contained therein to heat-cur it. The temperature of this heat treatment may be appropriately set depending on the type of thermosetting resin contained in the composite magnetic material, and examples of the temperature include a temperature of 150°C to 230°C, and further 160°C to 200°C. The heat treatment time may also be, for example, 0.1 hours to 5 hours, and further 0.2 hours to 3 hours. In addition, this heat treatment may be performed in a mold, may be performed after removal from the mold, or may be performed both. Thereafter, the obtained coil component can be selectively subjected to a process such as surface polishing or coating as necessary.

In this way, it is possible to easily obtain coil components in which the content of thermosetting resin in the composite magnetic thermosetting molded body containing the coil is maintained (the content of the composite magnetic material and the thermosetting resin are substantially the same). In other words, it is possible to easily manufacture coil components in which the decrease in the breakdown voltage when a DC voltage is applied is suppressed (for example, the breakdown voltage is 200 V/mm or more).

In addition, when a coil component is manufactured using a mold in which the discharge groove 31 is integrated with the wiring groove 33 as in the embodiment shown in FIG. 3, the composite magnetic material flows out from the periphery of the lead-out portion 103 of the coil during thermal molding, and the periphery of the lead-out portion 103 of the obtained coil component has a protrusion formed by thermally curing the remaining part of this composite magnetic material. In other words, a coil component can be obtained in which the periphery of the lead-out portion 103 of the coil has a protrusion in which a composite magnetic thermosetting molded body having substantially the same composition as the composite magnetic thermosetting molded body on the periphery of the coil winding portion 101 protrudes together with the lead-out portion 103. This coil component is likely to have higher resistance to wire bending in the lead-out portion 103 due to the protrusion on the periphery of the lead-out portion 103.

The above describes the manufacturing method of the coil component according to the present embodiment. However, the present invention is not limited to the above-described embodiment, and also includes various modifications, improvements, and other embodiments 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 and scope of the present invention.

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

As the metal magnetic powder used in the composite magnetic material, a mixture (maximum particle diameter 50 μm) of a nearly spherical Fe-Si-Cr-B amorphous powder (Fe content 86 wt%, Si content 6.7 wt%, Cr content 2.5 wt%, B content 2.5 wt%) with an average particle diameter (D ₅₀ ) of 27 μm and an average particle diameter (D ₅₀ ) of 4 μm was prepared. Here, the average particle diameter (D ₅₀ ) and the maximum particle diameter were values measured using a laser diffraction/scattering type particle size distribution measuring device (particle size distribution) LA-960 (manufactured by HORIBA Seisakusho Co., Ltd.). Furthermore, as the thermosetting resin used in the composite magnetic material, a novolac type epoxy resin to which a necessary amount of a phenol novolac type hardener was added as a hardener was prepared.

First, a predetermined amount of the thermosetting resin was weighed out and diluted with methyl ethyl ketone (MEK) as a solvent. The resin solution was thoroughly dissolved, and a predetermined amount of the metal magnetic powder was mixed into the resin solution, which was thoroughly stirred and mixed using a planetary mixer. The dilution solvent, methyl ethyl ketone (MEK), was then dried while stirring using the planetary mixer, yielding a mixture of the metal magnetic powder and the thermosetting resin. The mixture was then crushed using a high-speed crusher, and then granulated to produce a granulated powder of a composite magnetic material with a mass ratio of the thermosetting resin of 3.0 wt%.

Separately, an air-core coil was prepared using insulated copper wire (wire) having a winding section and an extension section from which the wire is pulled out.

Next, a mold was prepared having four discharge grooves formed by combining two discharge holes (discharge holes whose cross section perpendicular to the hole is substantially circular and substantially cylindrical) of the same size when the upper and lower dies of the mold are brought into contact in the region of the upper die that comes into contact with the lower die and in the region of the lower die that comes into contact with the upper die, and two wiring grooves in which the clearance (the distance between the inner surface of the wiring groove and the lead-out portion of the coil) generated when the lead-out portion of the coil is disposed is less than 50 μm. Note that 18 types of this mold were prepared, each differing in the shape of the internal space (No. 1 to No. 3) or the diameter of the discharge hole formed (0.050 mm to 1.000 mm). The surface area a ( ^mm2 ) of the coil parts produced using these dies, the diameter b (minimum hole diameter, mm) of one discharge hole of these dies, the total cross-sectional area c (total opening area, mm2) of the cross-sectional area of the two discharge holes of these dies perpendicular to the hole, and the ratio c/a ( ^% ) of the total cross-sectional area of the two discharge holes of these dies to the surface area of the coil parts produced using these dies are shown in Table 1 below. Then, the winding part of the air-core coil was placed inside each die, and the drawing part was placed in the wiring groove, and the granulated powder of the composite magnetic material was filled so that the winding part of the air-core coil was embedded. Then, the temperature of this die was set to 140°C, and compression molding was performed for 1 minute at a pressure of 100 kgf/ ^cm2 by the upper punch, and then the composite magnetic molded body was removed from the die. The removed composite magnetic molded body was heat treated under conditions of 160°C for 2 hours, and the thermosetting resin was heat-cured (after-cured) to obtain a coil part that is a composite magnetic thermosetting molded body containing a coil.

The dielectric breakdown voltage (V/mm) of the composite magnetic thermosetting molded body in each of the obtained coil parts was measured by sandwiching both main surfaces of the composite magnetic thermosetting molded body cut to a specified thickness between two copper plate electrodes via a conductive rubber sheet (thickness 0.3 mm) and applying a DC voltage. For the measurement, an insulation resistance meter SM7110 manufactured by Hioki E.E.C. was used. The results are also shown in Table 1 below.

These results show that the composite magnetic thermosetting molded bodies of all coil parts had a breakdown voltage of 230 V/mm or more. In other words, in all coil parts, separation of the metal magnetic powder and the thermosetting resin in the composite magnetic material did not occur during thermoforming, and the coil parts were molded and thermoset while maintaining the content of thermosetting resin.

The present embodiment encompasses the following technical ideas.
(1) A method for manufacturing a coil component in which a composite magnetic material composed of a metal magnetic powder and a thermosetting resin is molded and thermoset into a composite magnetic thermosetting molded body, the composite magnetic material being formed into a composite magnetic thermosetting molded body, and a wound portion of a coil is encapsulated in the composite magnetic thermosetting molded body, and a lead-out portion of the coil protrudes from the composite magnetic thermosetting molded body, the method comprising the steps of: (a) forming a wiring groove in which the lead-out portion of the coil is disposed in an area of the upper mold that comes into contact with the lower mold or an area of the lower mold that comes into contact with the upper mold; and (b) forming a wiring groove in which the lead-out portion of the coil is disposed in the wiring groove, the wiring groove having a diameter that allows the metal magnetic powder to pass through and a total opening area that is 0.01% of the surface area of the coil component when the lead-out portion of the coil is disposed in the wiring groove and the upper mold and the lower mold are brought into contact with each other. a compression molding process of preparing a mold having one or more discharge holes with a coefficient of thermal expansion of 0.003% or more and 1.5% or less, placing the winding portion of the coil inside the mold, placing the pull-out portion of the coil in a wiring groove so that the pull-out portion of the coil protrudes from inside the mold, filling the inside of the mold with the composite magnetic material so as to embed the winding portion of the coil, heating the mold, and compression molding the composite magnetic material while causing it to flow out of the discharge holes to obtain a composite magnetic molded body containing the winding portion of the coil, and a heat hardening process of heat treating the composite magnetic molded body to heat harden it, thereby obtaining the coil component.
(2) The method for manufacturing a coil component according to (1), wherein the discharge hole of the mold has a minimum hole diameter that is equal to or larger than the maximum particle diameter of the metal magnetic powder.
(3) A method for manufacturing a coil component described in (1) or (2), wherein the mold has an ejection groove in an area of the upper mold that comes into contact with the lower mold or in an area of the lower mold that comes into contact with the upper mold, and the ejection groove forms the ejection hole when the upper mold and the lower mold are brought into contact with each other.
(4) A method for manufacturing a coil component described in any one of (1) to (3), wherein the mold has a plurality of side peripheral surfaces, and among the side peripheral surfaces, a drawn-out portion protruding surface from which the drawn-out portion of the coil protrudes and a discharge hole opening surface from which the discharge hole opens have different configurations.
(5) The method for manufacturing a coil component according to any one of (1) to (4), wherein in the compression molding step, the mold is heated to 100° C. or more and 180° C. or less, and compression molding is performed at a molding pressure of 3 kgf/cm ² or more and 5000 kgf/cm ² or less for a time period of 10 seconds to 5 minutes.

11 Upper mold of mold 21 Lower mold of mold 31 Discharge groove 33 Wiring groove 35 Discharge hole 101 Coil winding portion 103 Coil drawing portion

Claims (5)

A method for manufacturing a coil component, comprising: a composite magnetic thermosetting molded body obtained by molding and thermosetting a composite magnetic material composed of a metal magnetic powder and a thermosetting resin; a wound portion of a coil is enclosed in the composite magnetic thermosetting molded body; and a pull-out portion of the coil protrudes from the composite magnetic thermosetting molded body,
a die having an upper die and a lower die, a wiring groove for arranging the lead-out portion of the coil in an area of the upper die that comes into contact with the lower die or an area of the lower die that comes into contact with the upper die, and further having one or more discharge holes having a hole diameter that allows the metal magnetic powder to pass through and a total opening area that is 0.003% or more and 1.5% or less of a surface area of the coil component when the lead-out portion of the coil is arranged in the wiring groove and the upper die and the lower die are in contact with each other;
a compression molding process in which the winding portion of the coil is disposed inside the mold, the drawn-out portion of the coil is disposed in the wiring groove so that the drawn-out portion of the coil protrudes from inside the mold, the composite magnetic material is filled inside the mold so as to embed the winding portion of the coil, the mold is heated, and the composite magnetic material is compression-molded while flowing out from the discharge hole, thereby obtaining a composite magnetic molded body containing the winding portion of the coil;
and a heat curing step of heat-treating the composite magnetic molded body to heat-cure it, thereby obtaining the coil component.
A manufacturing method for coil components. The method for manufacturing coil components according to claim 1, wherein the minimum diameter of the discharge hole of the die is equal to or greater than the maximum particle diameter of the metal magnetic powder. The method for manufacturing coil parts according to claim 1 or 2, wherein the die has a discharge groove in an area of the upper die that comes into contact with the lower die or in an area of the lower die that comes into contact with the upper die, and the discharge groove forms the discharge hole when the upper die and the lower die are brought into contact with each other. The method for manufacturing a coil component according to any one of claims 1 to 3, wherein the die has a plurality of side circumferential surfaces, and among the side circumferential surfaces, the pull-out portion protruding surface from which the pull-out portion of the coil protrudes and the discharge hole opening surface where the discharge hole opens are configured differently. The method for producing a coil component according to any one of claims 1 to 4, wherein in the compression molding step, the mold is heated to 100 ° C. or more and 180 ° C. or less, and compression molding is performed at a molding pressure of 3 kgf/cm ² or more and 5000 kgf/cm ² or less for 10 seconds to 5 minutes.

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