Coil-embedded inductor using ferrite core and its manufacturing method

Abstract

The present invention relates to a coil-embedded inductor using a ferrite core, which can prevent local concentration of magnetic flux density and improve inductance characteristics, and a manufacturing method thereof. The coil-embedded inductor using a ferrite core includes a ferrite core unit having one open side and a cavity formed therein, a coil unit having an insulating insert formed of an insulating plastic injection product on the surface of a wound coil and disposed in the cavity of the ferrite core unit, and a magnetic body formed by filling the remaining portion of the cavity of the ferrite core unit where the coil unit is not disposed with a magnetic molding liquid and hardening the magnetic body.

Description

[Technical Field]

[0001] The present invention relates to a coil-embedded inductor using a ferrite core and a manufacturing method thereof, and more particularly to a coil-embedded inductor using a ferrite core that can prevent local concentration of magnetic flux density and improve inductance characteristics, and a manufacturing method thereof. [Background technology]

[0002] Inductors, along with capacitors, are passive components essential to power conversion devices, reducing current ripple. These inductors are used in a variety of applications, including eco-friendly vehicles, solar inverters, ESS, and air conditioner inverters, and there is a growing demand for high inductance characteristics, low loss, and miniaturization and weight reduction.

[0003] The conventional method for manufacturing inductors involves compressing and molding metal powder to form a magnetic core, and then inserting a wound coil. However, this method has limitations in terms of the shape and size of the powder magnetic core, limiting the ability to manufacture inductors with a variety of shapes. The complexity of the processes from assembling the core to assembling the finished product also increases the manufacturing costs of inductors.

[0004] For this reason, research has recently been conducted into inductors that are manufactured by hardening soft magnetic molding liquid. Inductors that use such soft magnetic molding liquid have the advantage of being able to manufacture inductors of various shapes that are impossible to manufacture with conventional powder magnetic cores, and the manufacturing process is simple, allowing for significant reductions in the manufacturing costs of inductors.

[0005] However, since the magnetic permeability range of soft magnetic molding liquid is 26 to 60μ, there is a limit in that it is not possible to achieve high inductance characteristics compared to general magnetic cores.

[0006] Furthermore, a separate container having the shape of the mold is required to inject the magnetic paste, which increases the volume and cost of the inductor.

[0007] In particular, in the case of inductors in which a highly heat-resistant plastic resin is used as the container material and the coil is embedded in such a highly heat-resistant plastic resin, there is a problem in that it is difficult for the internal heat to be dissipated to the outside by the container made of plastic resin.

[0008] The content described above as background art is intended to provide a background understanding of the present invention and should not be construed as an admission that it corresponds to prior art known to those skilled in the art. Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention provides a coil-embedded inductor using a ferrite core that can prevent local concentration of magnetic flux density and improve inductance characteristics, and a method for manufacturing the same.

[0010] In particular, the present invention provides a coil-embedded inductor using a ferrite core, which prevents magnetic flux density from concentrating inside by forming a container made of a ferrite core on the outside where magnetic flux density concentration is relatively low, and which improves inductance characteristics and achieves miniaturization and weight reduction by filling a magnetic molding liquid for forming a magnetic body inside a container-shaped cavity made of a ferrite core whose specific gravity is smaller than that of a magnetic body, and a manufacturing method thereof.

[0011] The technical problems that the present invention aims to achieve are not limited to the above-mentioned technical problems, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description of the present invention. [Means for solving the problem]

[0012] A coil-embedded inductor using a ferrite core according to one embodiment of the present invention includes a ferrite core unit having an open side and a cavity formed therein, a coil unit having an insulating insert made of an insulating plastic injection material formed on the surface of a wound coil and placed in the cavity of the ferrite core unit, and a magnetic body formed by filling the remaining portion of the cavity of the ferrite core unit where the coil unit is not placed with a magnetic molding liquid and hardening it.

[0013] The ferrite core unit is divided into a plurality of ferrite cores, which are spaced apart from one another with gaps maintained therebetween.

[0014] The plurality of ferrite cores are arranged along the magnetic path direction so that at least one gap formed in the ferrite core unit is formed along the magnetic path direction formed by the coil unit.

[0015] The ferrite core unit includes a first ferrite core that surrounds the circumferential direction in which the coil provided in the coil unit is wound, and a pair of second ferrite cores that surround both ends of the coil provided in the coil unit, and the first ferrite core and the pair of second ferrite cores are arranged at a distance from each other.

[0016] An insulating frame made of an insulating plastic injection molding is disposed in a gap formed in the ferrite core unit.

[0017] The insulating frame includes a frame body surrounding an outer peripheral surface of the first ferrite core, and a gap plate disposed in a gap between the first ferrite core and the second ferrite core.

[0018] The relative magnetic permeability of the ferrite core unit is greater than the relative magnetic permeability of the magnetic body.

[0019] The ferrite core unit has a relative magnetic permeability of 200μ or more, and the magnetic body has a relative magnetic permeability of 26 to 60μ.

[0020] The insulating insert of the coil unit is characterized by being formed of a plastic resin having a thermal conductivity of 2 W / mk or more.

[0021] On the other hand, a method for manufacturing a coil-embedded inductor using a ferrite core according to one embodiment of the present invention includes the steps of (I) preparing a magnetic molding liquid, (II) preparing a coil unit whose surface is insulated with plastic resin, (III) preparing a ferrite core unit having a cavity into which the magnetic molding liquid is filled, (IV) placing the coil unit in the cavity of the ferrite core unit, (V) filling the cavity of the ferrite core unit with the prepared magnetic molding liquid, and (VI) hardening the magnetic molding liquid filled in the ferrite core unit to form a magnetic body that is integrated with the ferrite core unit and the coil unit.

[0022] In the step (I), the relative magnetic permeability of the magnetic molding liquid is 26 to 60μ, and in the step (III), the relative magnetic permeability of the ferrite core unit is 200μ or more.

[0023] In the step (I), the density of the magnetic molding liquid is 5.5 to 6.5 g / cc.

[0024] The step (I) includes the steps of (I-1) preparing an organic vehicle by stirring a polymer resin and a solvent, and (I-2) preparing a magnetic molding liquid by kneading a magnetic powder with the organic vehicle.

[0025] In the step (I-1), the polymer resin includes one or more selected from the group consisting of epoxy resin, epoxy acrylate resin, acrylic resin, silicone resin, phenoxy resin, and urethane resin.

[0026] In the step (I-2), the magnetic powder includes one or more selected from the group consisting of pure iron, carbonyl iron, iron-silicon alloy (Fe-Si alloy), iron-silicon-chromium alloy (Fe-Si-Cr alloy), sand dust (Fe-Si-Al alloy), permalloy, molybdenum permalloy (Mo-permalloy), and amorphous powder.

[0027] In the step (I-2), the magnetic powder is characterized in that it is a mixture of two or more types of magnetic powders having different average particle sizes.

[0028] The step (II) includes the steps of (II-1) preparing a wound coil, and (II-2) preparing a coil unit by injecting plastic resin into a mold into which the prepared coil is inserted.

[0029] In the step (II-2), the plastic resin has a thermal conductivity of 2 W / mk or more.

[0030] In the step (II-2), the injection of the plastic resin is carried out in at least two separate steps.

[0031] The step (III) includes the steps of (III-1) preparing a ferrite core divided into multiple pieces, and (III-2) spacing the ferrite core divided into multiple pieces along the magnetic path direction formed by the coil unit so that at least one gap is formed along the magnetic path direction.

[0032] The step (III) further includes the steps of (III-3) preparing an insulating frame for fixing the divided ferrite cores at a distance from each other, and (III-4) mounting the divided ferrite cores at a distance from each other on the prepared insulating frame so that gaps are maintained between the divided ferrite cores. [Effects of the Invention]

[0033] According to the embodiment of the present invention, the following effects can be expected.

[0034] First, by placing a ferrite core with high magnetic permeability and low saturation magnetic flux density on the outside of an inductor with a relatively low magnetic flux density, the inductance characteristics can be improved compared to inductors manufactured by hardening only conventional soft magnetic molding liquid.

[0035] Second, by replacing the separate non-magnetic container for filling the magnetic molding liquid with a ferrite core, a volume reduction effect can be expected.

[0036] Third, by using a ferrite core, which has a smaller specific gravity than metal powder, a weight reduction effect can be expected.

[0037] According to the embodiments of the present invention, the effects of the present invention are not limited to the above-described effects, but include all effects that can be inferred from the configuration of the invention described in the detailed description of the present invention or the claims. [Brief explanation of the drawings]

[0038] [Figure 1] 1 is a perspective view showing a coil-embedded inductor using a ferrite core according to an embodiment of the present invention; [Figure 2] 1 is an exploded perspective view showing a coil-embedded inductor using a ferrite core according to an embodiment of the present invention. [Figure 3] 1A to 1C are perspective views showing steps for manufacturing a coil-embedded inductor using a ferrite core according to an embodiment of the present invention. [Figure 4] 1 is a flowchart showing steps for manufacturing a coil-embedded inductor using a ferrite core according to an embodiment of the present invention. [Figure 5] 10 is a graph comparing inductance, which is a magnetic characteristic of the inductors according to the comparative example and the example. DETAILED DESCRIPTION OF THE INVENTION

[0039] Hereinafter, the embodiments of the present invention will be described in more detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and may be realized in various different forms. The present embodiments are provided merely to complete the disclosure of the present invention and to enable those skilled in the art to fully understand the scope of the invention. In the drawings, the same reference numerals refer to the same elements.

[0040] FIG. 1 is an oblique view showing a coil-embedded inductor using a ferrite core according to one embodiment of the present invention, FIG. 2 is an exploded oblique view showing a coil-embedded inductor using a ferrite core according to one embodiment of the present invention, and FIG. 3 is an oblique view showing steps for manufacturing a coil-embedded inductor using a ferrite core according to one embodiment of the present invention.

[0041] As shown in the figure, the coil-embedded inductor using a ferrite core according to one embodiment of the present invention includes a ferrite core unit 100, a coil unit 200, and a magnetic body 300.

[0042] The ferrite core unit 100 has one open side and a cavity 101 formed inside, and serves as a container when molding the magnetic body 300. In particular, in this embodiment, the ferrite core unit 100 not only serves as a container but also prevents magnetic flux density from concentrating locally in the inner region of the inductor, thereby improving inductance characteristics.

[0043] Therefore, it is preferable that the ferrite core unit 100 has a smaller specific gravity and a larger relative magnetic permeability than the magnetic body.

[0044] From this point of view, it is preferable that the ferrite core 110 constituting the ferrite core unit 100 is manufactured using ferrite having a relative magnetic permeability of 200μ or more.

[0045] In particular, in order to improve the DC superposition characteristics of the ferrite core 110, the ferrite core unit 100 divides the ferrite core 110 into a plurality of pieces, which are spaced apart with gaps maintained between them.

[0046] In this case, it is preferable to arrange multiple divided ferrite cores 110 along the magnetic path direction so that at least one gap formed in the ferrite core unit 100 is formed along the magnetic path direction formed by the coil unit 200.

[0047] For example, as shown in FIG. 2, the ferrite core unit 100 includes a first ferrite core 111 that surrounds the circumferential direction in which the coil 210 provided in the coil unit 200 is wound, and a pair of second ferrite cores 112 that surround both ends of the coil 210 provided in the coil unit 200.

[0048] At this time, the first ferrite core 111 and the pair of second ferrite cores 112 are spaced apart from each other to form a gap 102 therebetween. For example, the gap 102 formed by the separation between the first ferrite core 111 and the pair of second ferrite cores 112 may be set to 1 mm. Of course, the number and size of the gaps 102 are preferably determined according to the inductance characteristics required of the inductor.

[0049] In particular, in order to maintain the posture of the first ferrite core 111 and the pair of second ferrite cores 112 and to stably form the gap 102, an insulating frame 120 formed from an insulating plastic injection molding may be placed in the gap 102 formed in the ferrite core unit 100.

[0050] In this case, the insulating frame 120 includes a frame body 121 surrounding the outer peripheral surface of the first ferrite core 111 and a gap plate 122 disposed in the gap 102 between the first ferrite core 111 and the second ferrite core 112.

[0051] The frame body 121 is formed in the shape of a plate bent in a substantially "⊂" shape. A pair of gap plates 122 are integrally formed on the inner peripheral surface of the frame body 121.

[0052] In this case, it is preferable that the insulating frame 120 is formed by injecting plastic resin. Of course, the insulating frame 120 is not limited to plastic resin as long as it can maintain insulation properties.

[0053] Furthermore, the outer peripheral surface of the frame body 121 may be formed with fastening portions 123 that can fix the inductor to bolts inside the power conversion device.

[0054] The coil unit 200 is configured by forming an insulating insert 220 made of an insulating plastic injection material on the surface of a wound coil 210.

[0055] At this time, the insulating insert 220 is preferably made of a plastic resin having a thermal conductivity of 2 W / mk or more, so that the heat generated from the coil during operation of the inductor can be smoothly transferred to the outside and dissipated.

[0056] The magnetic body 300 is formed by filling the remaining portion of the cavity 101 of the ferrite core unit 100 where the coil unit 200 is not disposed with a magnetic molding liquid 310 and then hardening it.

[0057] Therefore, the magnetic body 300 is maintained in a state of being separated by the coil 210 and the insulating insert 220 that constitute the coil unit 200 .

[0058] At this time, the relative magnetic permeability of the magnetic body 300 is smaller than the relative magnetic permeability of the first ferrite core 111 and the second ferrite core 112 that constitute the ferrite core unit 100. For example, the relative magnetic permeability of the magnetic body 300 is 26 to 60μ.

[0059] A method for manufacturing a coil-embedded inductor using a ferrite core configured as above will be described with reference to the drawings.

[0060] FIG. 3 is an oblique view showing the steps for manufacturing a coil-embedded inductor using a ferrite core according to one embodiment of the present invention, and FIG. 4 is a procedural diagram showing the steps for manufacturing a coil-embedded inductor using a ferrite core according to one embodiment of the present invention.

[0061] As shown in the figure, a method for manufacturing a coil-embedded inductor using a ferrite core according to one embodiment of the present invention includes the steps of (I) preparing a magnetic molding liquid, (II) preparing a coil unit whose surface is insulated with plastic resin, (III) preparing a ferrite core unit having a cavity into which the magnetic molding liquid is filled, (IV) placing the coil unit in the cavity of the ferrite core unit, (V) filling the cavity of the ferrite core unit with the prepared magnetic molding liquid, and (VI) hardening the magnetic molding liquid filled in the ferrite core unit to form a magnetic body integrated with the ferrite core unit and the coil unit.

[0062] Each of the above steps will now be described in more detail.

[0063] (I) Step of preparing magnetic molding liquid The step of preparing a magnetic molding liquid is a step of preparing a magnetic molding liquid 310 for forming the magnetic body 300 in the internal region where the magnetic flux density is high when manufacturing an inductor. The step of preparing the magnetic molding liquid is carried out through the following detailed steps, for example, but it is not necessary to carry out only these detailed steps.

[0064] (I-1) A process of preparing an organic vehicle by mixing a polymer resin and a solvent The organic vehicle is prepared by stirring a polymer resin and a solvent, and the polymer resin may be one or more polymer resins selected from the group consisting of, but not limited to, epoxy resins, epoxy acrylate resins, acrylic resins, silicone resins, phenoxy resins, and urethane resins.

[0065] The polymer resin functions as a binder for the magnetic powder, and such functions include, but are not limited to, a structural material that maintains the shape of the magnetic core, a chemical resistance to various organic solvents, a bond and support between the magnetic powder and additives in the organic vehicle to maintain the desired shape, and a filler for filling the spaces between the magnetic powder to improve the insulation of the magnetic body and to increase the resistivity of the magnetic core to reduce eddy current loss in the magnetic body.

[0066] The solvent may include, but is not limited to, one or more selected from the group consisting of methyl cellosolve, ethyl cellosolve, butyl cellosolve, butyl cellosolve acetate, aliphatic alcohol, terpineol, dihydroterpineol, ethylene glycol, ethyl carbitol, butyl carbitol, butyl carbitol acetate, texanol, methyl ethyl ketone, ethyl acetate, and cyclohexanone. The suggested composition ratio of polymer resin to solvent is 50-60 wt% polymer resin and 40-50 wt% solvent. If the polymer resin is less than 50 wt% or the solvent is more than 50 wt%, the binding function of the polymer resin will be reduced, and problems with the strength of the inductor may occur, such as partial detachment of the magnetic powder or partial cracks occurring in the magnetic core after the magnetic molding liquid hardens.If the polymer resin is more than 60 wt% or the solvent is less than 50 wt%, the amount of polymer resin will be excessive, and the magnetic molding liquid may leak out due to swelling of the polymer when it hardens.

[0067] Additionally, the components of the organic vehicle can affect the hardened density of the magnetic molding fluid; increasing the proportion of high-density materials in the organic vehicle will increase the hardened density of the magnetic molding fluid, and increasing the proportion of low-density materials will decrease the hardened density of the magnetic molding fluid.

[0068] The organic vehicle may contain one or more additives selected from the group consisting of a dispersant, a stabilizer, a catalyst, and a catalyst activator. If the polymer resin is not uniformly distributed in the solvent and may aggregate, a dispersant can be added to prevent such aggregation. If it is necessary to suppress chemical changes or state changes in the organic vehicle, a stabilizer can be added. If the polymer resin and the solvent are not mixed smoothly, a catalyst or a catalyst activator can be used to promote the reaction.

[0069] The process of preparing an organic vehicle by stirring the polymer resin and solvent (including additives, if any) can be carried out using a mechanical stirrer at a predetermined rpm for a predetermined time. While there is no upper limit to the stirring time, it is important to note the minimum time required to ensure uniform stirring. This time varies depending on the type of polymer resin, the type of solvent, and the composition between the polymer resin and the solvent, so it must be determined on a case-by-case basis. After stirring, the prepared organic vehicle may be further subjected to a degassing process by filtering out impurities using a sieve. Degassing will be described in detail later.

[0070] (I-2) A process of preparing a magnetic molding liquid by kneading magnetic powder with an organic vehicle. The magnetic molding liquid is produced by kneading the magnetic powder with an organic vehicle. The magnetic powder and organic vehicle are weighed and placed in a kneader, and then kneaded for a predetermined time so that the magnetic powder and organic vehicle are uniformly mixed. There is no upper limit to the time required for the kneading process, but attention must be paid to the minimum time required to ensure uniform mixing. This varies depending on the type of magnetic powder, the ingredients and composition of the organic vehicle, and the composition between the magnetic powder and the organic vehicle, and must be determined on a case-by-case basis.

[0071] The magnetic powder may include, but is not limited to, one or more selected from the group consisting of pure iron, carbonyl iron, iron-silicon alloy (Fe-Si alloy), iron-silicon-chromium alloy (Fe-Si-Cr alloy), sand dust (Fe-Si-Al alloy), permalloy, molybdenum permalloy (Mo-permalloy), and amorphous powder.

[0072] We recommend that the average particle size of the magnetic powder be 10 to 150 μm. If the average particle size of the magnetic powder exceeds 150 μm, the packing rate of the magnetic powder will decrease, resulting in a decrease in hardening density, and problems such as clogging of the dispenser nozzle when injecting the magnetic molding liquid may occur. If the average particle size of the magnetic powder is less than 10 μm, eddy current loss in the magnetic core may become an issue, and the organic vehicle may not be able to sufficiently fill the spaces between the magnetic powder particles, resulting in problems with the strength of the magnetic core.

[0073] The magnetic powder may be composed of a mixture of two or more types of magnetic powders with different average particle sizes. In this case, the magnetic powder with a smaller average particle size is positioned between magnetic powders with a larger average particle size, resulting in an increased hardened density of the magnetic molding liquid. The hardened density of the magnetic molding liquid will be described later. When mixing two or more types of magnetic powders with different average particle sizes, we suggest mixing a first magnetic powder with an average particle size of 2 to 5 μm, a second magnetic powder with an average particle size of 10 to 20 μm, and a third magnetic powder with an average particle size of 50 to 150 μm. This is because the magnetic powder with a smaller average particle size is positioned between magnetic powders with a larger average particle size.

[0074] The magnetic molding liquid preferably has a composition ratio of 94 to 98 wt% magnetic powder and 2 to 6 wt% organic vehicle. If the magnetic powder exceeds 98 wt% or the organic vehicle is less than 2 wt%, the amount of magnetic powder is too excessive, which may make it impossible to produce the magnetic molding liquid by filling it with magnetic powder. If the amount of organic vehicle is too small, the flow of the magnetic molding liquid may be poor in terms of rheology when it is poured into the case, which may cause partial cracks in the magnetic core. Furthermore, the binding function of the polymer resin may be reduced, which may cause partial detachment of the magnetic powder after the magnetic molding liquid hardens, which may increase eddy current loss in the magnetic core. If the magnetic powder is less than 94 wt% or the organic vehicle is more than 6 wt%, there are advantages in terms of rheology, but the amount of organic vehicle is too much and the loading amount of magnetic powder is reduced, which may result in a decrease in the relative permeability of the magnetic core and a decrease in inductance characteristics, and if the amount of polymer resin is too much, the polymer may swell when the magnetic molding liquid hardens, causing the magnetic molding liquid to leak out of the case cavity.

[0075] Furthermore, the relative magnetic permeability of the magnetic molding liquid produced with the above composition ratio is preferably 26μ or more. This is because if the relative magnetic permeability of the magnetic molding liquid is less than 26μ, the inductance characteristics will decrease. On the other hand, if the relative magnetic permeability of the magnetic molding liquid exceeds 60μ, there is a drawback in that the manufacturing cost of the magnetic molding liquid increases. For this reason, the relative magnetic permeability of the magnetic molding liquid is preferably about 26 to 60μ.

[0076] The reason for limiting the range of relative magnetic permeability of the magnetic molding liquid in this way is that, within the range of use of the inductor of the present invention, it is required to have high inductance in the low current region and maintain inductance even in the high current region. This is proportional to the efficiency characteristics of the system, and takes into consideration the relative magnetic permeability that may occur when producing a magnetic molding liquid with the above composition ratio.

[0077] One of the performance requirements for magnetic molding fluid is its cured density, which is directly related to the composition ratio of magnetic powder to organic vehicle. Considering that the density of magnetic powder is greater than that of the organic vehicle, the density of the magnetic molding fluid increases as the proportion of magnetic powder increases, which means that the relative permeability of the magnetic molding fluid increases. Conversely, the density of the magnetic molding fluid decreases as the proportion of magnetic powder decreases, which means that the relative permeability of the magnetic molding fluid decreases, but it also means that eddy current loss decreases. In consideration of the relative permeability and eddy current loss, we recommend that the density of the magnetic molding fluid be 5.5 to 6.5 g / cc. This ensures high overall permeability and also reduces eddy current loss to some extent.

[0078] Before proceeding to the next step, a curing agent and / or curing accelerator may be added to the magnetic molding liquid to accelerate curing of the magnetic molding liquid. Curing agents include, but are not limited to, aliphatic amines, modified aliphatic amines, aromatic amines, modified aromatic amines, acid anhydrides, polyamides, and imidazoles. Curing accelerators include, but are not limited to, Lewis acids, alcohols, phenols, alkylphenols, carboxylic acids, tertiary amines, and imidazoles. The use of these agents can shorten the time required for curing the magnetic molding liquid.

[0079] In addition, the magnetic molding liquid can be degassed before proceeding to the next step. Degassing refers to removing air bubbles contained in the magnetic molding liquid, and this process can improve inductance loss. Furthermore, air bubbles present in the magnetic molding liquid not only reduce the impact resistance of the magnetic core, but can also induce cracks inside the magnetic core if moisture penetrates the bubbles, so the degassing process of the magnetic molding liquid is extremely important. A commercially available agitator / defoamer can be used to rotate and revolve the magnetic molding liquid to degas it, but the method is not limited to this.

[0080] (II) Step of preparing a coil unit

[0081] (II-1) The process of preparing the wound coil The coil 210 is prepared by winding it into a circular, oval or rectangular shape. In this case, the shape and material of the coil 210 are not limited to a specific shape and material, and are preferably determined according to the shape of the inductor and the inductance characteristics required of the inductor.

[0082] (II-2) The process of preparing the coil unit The process of preparing the coil unit is a process of injecting plastic resin onto the surface of the prepared coil 210 so as to maintain insulation between the coil 210 and the magnetic molding liquid 310 when the magnetic molding liquid 310 is subsequently filled into the cavity of the ferrite core unit 100.

[0083] More specifically, the prepared coil 210 is inserted into a mold, and plastic resin is injected into the cavity of the mold to form an insulating insert 220 on the surface of the coil 210, thereby preparing the coil unit 200.

[0084] At this time, the injection process may be performed two or more times to inject the insulating insert 220 into a desired shape.

[0085] Furthermore, the plastic resin injected to form the insulating insert 220 is preferably a heat-dissipating plastic resin having a thermal conductivity of W / mk or more so that the heat of the coil 210 can be easily dissipated to the outside.

[0086] (III) Step of preparing a ferrite core unit This is a step of preparing a ferrite core unit 100 having a cavity 101 formed therein into which a magnetic molding liquid 310 is to be filled.

[0087] At this time, the ferrite core unit 100 serves as a container into which the magnetic molding liquid 310 is filled.

[0088] (III-1) The process of preparing the ferrite core A plurality of divided ferrite cores 110 are prepared. The ferrite cores 110 are made of a material that is generally used for inductors, and detailed descriptions of the characteristics and manufacturing methods of each core will be omitted.

[0089] However, the ferrite core 110 prepared in this embodiment is prepared to achieve magnetic properties that cannot be achieved with the magnetic molding liquid 310, and it is important that the ferrite core 110 has a larger relative magnetic permeability than the magnetic molding liquid 310. For example, the relative magnetic permeability of the ferrite core 110 is preferably 200 μ or more. On the other hand, there is no particular upper limit to the relative magnetic permeability of the ferrite core 110.

[0090] (III-2) The process of spacing and arranging the divided ferrite cores In order to improve the DC superposition characteristics, the ferrite core 110 is divided into a plurality of pieces, which are spaced apart with gaps 102 maintained between them.

[0091] In this case, it is preferable that the divided ferrite core 110 is divided into multiple pieces and spaced apart along the magnetic path direction formed by the coil unit 200 so that at least one gap 102 is formed along the magnetic path direction.

[0092] For example, the ferrite core 110 includes a first ferrite core 111 arranged in an approximately "⊂" shape that surrounds the circumferential direction in which the coil 210 provided in the coil unit 200 is wound, and a pair of flat second ferrite cores 112 that surround both ends of the coil 210 provided in the coil unit 200.

[0093] Therefore, by arranging the second ferrite core 112 at both ends of the first ferrite core 111, one side is opened while maintaining the shape of a substantially rectangular parallelepiped, and a cavity 101 can be formed inside.

[0094] (III-3) Preparation of the insulating frame The process of preparing the insulating frame is a process of preparing the insulating frame 120 for fixing the divided ferrite core 110 in a spaced apart state.

[0095] In this case, the insulating frame 120 may be formed in a shape including a frame main body 121 surrounding the outer peripheral surface of the first ferrite core 111 and a gap plate 122 arranged in the gap 102 between the first ferrite core 111 and the second ferrite core 112.

[0096] (III-4) Attaching the ferrite core to the insulating frame The divided ferrite cores 110 are attached to the prepared insulating frame 120 at intervals so that the gaps 102 are maintained between them.

[0097] At this time, in order to attach the ferrite core 110, an epoxy or silicone adhesive may be injected into the attachment portion with the insulating frame 120. The adhesive may be injected into the joining surface of the ferrite core 110 using a syringe or a dispenser, but other methods are also possible. The adhesive is preferably cured in a curing oven at 80°C or higher, or left at room temperature to naturally harden.

[0098] (IV) Step of placing the coil unit in the cavity of the ferrite core unit This is a step of placing the prepared coil unit 200 in the cavity 101 formed in the ferrite core unit 100, where most of the coil unit 200 is placed in the cavity 101 formed in the ferrite core unit 100, and both side ends of the coil 210 constituting the coil unit 200 are placed so as to be exposed to the outside of the cavity 101 formed in the ferrite core unit 100 for connection with other components.

[0099] (V) A step of filling the cavity of the ferrite core unit with the prepared magnetic molding liquid. The step of filling the magnetic molding liquid is a step of filling the cavity 101 formed in the ferrite core unit 100 with the prepared magnetic molding liquid 310 in order to integrate the magnetic molding liquid 310 and the ferrite core unit 100.

[0100] At this time, the magnetic molding liquid 310 is injected into the cavity 101 formed in the ferrite core unit 100 through an upper portion of the cavity 101. The magnetic molding liquid 310 may be injected into the cavity 101 of the ferrite core unit 100 using a pump and a tube or a dispenser, but other methods are also possible.

[0101] (VI) Step of forming a magnetic material This is a step in which the magnetic molding liquid 310 filled in the ferrite core unit 100 is hardened to form the magnetic body 300 that is integrated with the ferrite core unit 100 and the coil unit 200.

[0102] The method for curing the magnetic molding liquid 310 is preferably vacuum curing, in which the magnetic molding liquid 310 is cured in a vacuum atmosphere, but is not limited to this.

[0103] When the magnetic molding liquid 310 is evacuated, there is an advantage that bubbles in the magnetic molding liquid can be removed by appropriately setting the temperature and curing time.

[0104] After preparing the inductor using the above method, the enamel coating on the coil end is removed to form a current-carrying portion in the coil to form a current-carrying path for connecting the inductor to a circuit component. The coating can be removed chemically or mechanically. The coil end can then be attached to the circuit component by welding, soldering, or bolts, or it can be made to be flexibly attached by connecting a coated stranded wire.

[0105] The present invention will be described below with reference to examples and comparative examples.

[0106] [Example: Manufacturing of a coil-embedded inductor using a magnetic molding liquid with a magnetic permeability of 35μ and a ferrite core with a magnetic permeability of 2000μ] To manufacture a coil-embedded inductor with an inductance characteristic of 1,000 μH, a magnetic molding liquid with a relative permeability of 35 μ was first prepared by kneading epoxy resin, iron-silicon-chromium alloy powder, sand dust powder, and other magnetic powders (one or more selected from the above-mentioned possible magnetic powders).

[0107] A 9.0mm (width) x 0.5mm (thickness) square coil with 36 turns was prepared and inserted using plastic injection molding to prepare a coil unit. After that, an insulating frame was prepared to form a 1mm thick gap in the magnetic path direction, and five ferrite cores with a relative magnetic permeability of 2,000μ were attached to each of the insulating frames.

[0108] Thereafter, the coil unit was placed in the cavity of the ferrite core unit, and the magnetic molding liquid was injected to fill the cavity. Next, the ferrite core unit filled with the magnetic molding liquid was placed in a vacuum oven, and the magnetic molding liquid was vacuum cured.

[0109] As a result, a coil-embedded inductor measuring 68 mm (width) × 52 mm (length) × 48 mm (height) was manufactured.

[0110] [Comparative example: Coil-embedded inductor manufactured using soft magnetic molding liquid with a relative magnetic permeability of 60μ] To manufacture an inductor (comparison example) with an inductance characteristic of 900 μH, an inductor of the same size and with the same coil and number of turns as the example, and the same volume, was manufactured in the same manner as the example by injecting and applying magnetic molding liquid with a relative permeability of 60 μ into the entire plastic case.

[0111] [Experimental example: Inductance measurement] The inductance of the coil-buried inductors manufactured in the examples and comparative examples was measured using a precision LCR meter (Keysight E4980A), and the results are shown in FIG.

[0112] As can be seen from FIG. 5, compared to the comparative example, the working example ensures high inductance even at low currents, and it was confirmed that high inductance can be ensured in most sections up to the maximum load current region.

[0113] Therefore, it was confirmed that by using a coil-embedded inductor in which a magnetic molding liquid is applied inside a ferrite core unit, it is possible to manufacture a coil-embedded inductor with higher inductance than an inductor that uses only a magnetic molding liquid.

[0114] Although the present invention has been described with reference to the accompanying drawings and the above-mentioned preferred embodiments, the present invention is not limited thereto but is limited only by the claims that follow. Therefore, a person skilled in the art may make various modifications and alterations to the present invention without departing from the technical spirit of the claims that follow. [Explanation of symbols]

[0115] 100: Ferrite core unit 101: Cavity 102: Air gap 110: Ferrite core 111: First ferrite core 112: Second ferrite core 120: Insulation frame 121: Frame body 122: gap plate 123: fastening part 200: Coil unit 210: Coil 220: Insulating insert 300: Magnetic material 310: Magnetic molding liquid

Claims

1. a ferrite core unit having an open surface and a cavity formed inside; a coil unit in which an insulating insert made of an insulating plastic injection material is formed on the surface of a wound coil and is disposed in a cavity of the ferrite core unit; a magnetic body formed by filling a remaining portion of the cavity of the ferrite core unit where the coil unit is not disposed with a magnetic molding liquid and hardening the magnetic body, The ferrite core unit is divided into a plurality of ferrite cores, which are spaced apart with gaps maintained between them. A coil-embedded inductor using a ferrite core.

2. The plurality of ferrite cores are arranged along a magnetic path direction so that at least one gap formed in the ferrite core unit is formed along the magnetic path direction formed by the coil unit. A coil-embedded inductor using the ferrite core according to claim 1.

3. The ferrite core unit is a first ferrite core that surrounds the coil unit in a circumferential direction around which the coil is wound; a pair of second ferrite cores surrounding both ends of the coil provided in the coil unit, The first ferrite core and the pair of second ferrite cores are spaced apart from each other. A coil-embedded inductor using the ferrite core according to claim 2.

4. An insulating frame made of insulating plastic injection material is disposed in the gap formed in the ferrite core unit. A coil-embedded inductor using the ferrite core according to claim 3.

5. The insulating frame is a frame body surrounding an outer peripheral surface of the first ferrite core; a gap plate disposed in the gap between the first ferrite core and the second ferrite core. A coil-embedded inductor using the ferrite core according to claim 4.

6. The relative permeability of the ferrite core unit is greater than the relative permeability of the magnetic body. A coil-embedded inductor using the ferrite core according to claim 1.

7. The relative permeability of the ferrite core unit is 200 μ or more, The relative permeability of the magnetic material is 26 to 60 μ A coil-embedded inductor using the ferrite core according to claim 6.

8. The insulating insert of the coil unit is made of a plastic resin having a thermal conductivity of 2 W / mk or more. A coil-embedded inductor using the ferrite core according to claim 1.

9. (I) providing a magnetic molding liquid; (II) preparing a coil unit whose surface is insulated with plastic resin; (III) preparing a ferrite core unit having a cavity formed therein to be filled with the magnetic molding liquid; (IV) placing the coil unit in the cavity of the ferrite core unit; (V) filling the cavity of the ferrite core unit with the prepared magnetic molding liquid; (VI) hardening the magnetic molding liquid filled in the ferrite core unit to form a magnetic body integrated with the ferrite core unit and the coil unit, The step (III) comprises: (III-1) a step of preparing a ferrite core divided into a plurality of pieces; (III-2) A step of arranging a plurality of divided ferrite cores along a magnetic path direction formed by the coil unit so that at least one gap is formed along the magnetic path direction.

1. A method for manufacturing a coil-embedded inductor using a ferrite core.

10. (I) providing a magnetic molding liquid; (II) preparing a coil unit whose surface is insulated with plastic resin; (III) preparing a ferrite core unit having a cavity formed therein to be filled with the magnetic molding liquid; (IV) placing the coil unit in the cavity of the ferrite core unit; (V) filling the cavity of the ferrite core unit with the prepared magnetic molding liquid; (VI) hardening the magnetic molding liquid filled in the ferrite core unit to form a magnetic body integrated with the ferrite core unit and the coil unit, The step (II) (II-1) preparing a wound coil; (II-2) preparing a coil unit by injecting plastic resin into a mold into which the prepared coil is inserted; In the step (II-2), the injection of the plastic resin is carried out in at least two separate injections, The step (III) comprises: (III-3) preparing an insulating frame for fixing the divided ferrite cores in a spaced apart state; (III-4) A process of attaching the divided ferrite cores to the prepared insulating frame at a distance so that gaps are maintained between the divided ferrite cores.

1. A method for manufacturing a coil-embedded inductor using a ferrite core.

11. In the step (I), the relative magnetic permeability of the magnetic molding liquid is 26 to 60 μm; In the step (III), the relative permeability of the ferrite core unit is 200 μ or more. A method for manufacturing a coil-embedded inductor using the ferrite core according to claim 9 or 10.

12. In step (I), the density of the magnetic molding liquid is 5.5 to 6.5 g / cc. A method for manufacturing a coil-embedded inductor using the ferrite core according to claim 11.

13. The step (I) (I-1) a step of preparing an organic vehicle by stirring a polymer resin and a solvent; (I-2) a step of kneading the magnetic powder with the organic vehicle to prepare a magnetic molding liquid. A method for manufacturing a coil-embedded inductor using the ferrite core according to claim 9 or 10.

14. In the process (I-1), The polymer resin includes one or more selected from the group consisting of epoxy resin, epoxy acrylate resin, acrylic resin, silicone resin, phenoxy resin, and urethane resin. A method for manufacturing a coil-embedded inductor using the ferrite core according to claim 13.

15. In the process (I-2), The magnetic powder includes one or more selected from the group consisting of pure iron, carbonyl iron, iron-silicon alloy (Fe-Si alloy), iron-silicon-chromium alloy (Fe-Si-Cr alloy), Sendust (registered trademark) (Fe-Si-Al alloy), permalloy, molybdenum permalloy (Mo-permalloy), and amorphous powder. A method for manufacturing a coil-embedded inductor using the ferrite core according to claim 13.

16. In the process (I-2), The magnetic powder is a mixture of two or more types of magnetic powders having different average particle sizes. A method for manufacturing a coil-embedded inductor using the ferrite core according to claim 13.

17. The step (II) (II-1) preparing a wound coil; (II-2) A step of preparing a coil unit by injecting plastic resin into a mold into which the prepared coil is inserted. A method for manufacturing a coil-embedded inductor using the ferrite core according to claim 9.

18. In the step (II-2), the plastic resin has a thermal conductivity of 2 W / mK or more. A method for manufacturing a coil-embedded inductor using the ferrite core according to claim 10.

19. In the step (II-2), the plastic resin is injected in at least two separate steps. A method for manufacturing a coil-embedded inductor using the ferrite core according to claim 17.

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