JP2022153771A - Inductor and manufacturing method thereof - Google Patents

Abstract

To provide an inductor with high inductance and excellent current and voltage resistance.SOLUTION: The inductor includes a coil 11 wound with flat conductor wire covered with insulation embedded in a molded body 12 containing metal magnetic powder and a binder material. A coating layer 18 is provided between the winding portion of the coil 11 and the molded body 12. The minimum thickness at the corners of the coil winding of the coating layer 18 is 25% or more of the average thickness of the outer peripheral surface of the coil winding part of the coating layer.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to an inductor in which a coil is formed by winding a conductive wire, and the coil is embedded in a molded body made of a composite magnetic material containing magnetic powder and a binder material, and a method for manufacturing the same.

In recent years, there has been an increasing need for miniaturization of electronic components in mobile phones and in-vehicle devices. On the other hand, a coil component designed to obtain a predetermined inductance value even in a small size has been developed by embedding a coil inside a magnetic material. In particular, in-vehicle devices are required to allow a larger current to flow, and a coil wound with a flat wire is used.

For example, Patent Document 1 is known as prior art document information related to the invention of this application.

JP 2014-49597 A

Normally, a coil is wound with an insulation-coated conductor wire, but if a rectangular conductor wire is wound and metallic magnetic powder is used as the magnetic material, the insulation coating becomes thin at the corners of the wound coil, and the dielectric breakdown voltage tends to deteriorate. .

In order to solve the above-mentioned problems, the present invention provides a coil wound with a flat conductor wire coated with insulation, and an inductor in which the coil is embedded in a composite magnetic material containing a metal magnetic powder and a binder material. A coating layer is provided between the winding portion and the composite magnetic material. % or more.

By carrying out as described above, an inductor having high inductance and excellent current resistance and voltage resistance can be obtained.

1 is a perspective perspective view of an inductor in one embodiment of the present invention; FIG. Sectional view of an inductor in one embodiment of the present invention FIG. 2 is a top view of a coil and a fixed frame in one embodiment of the present invention; A diagram of a coil coating process in one embodiment of the present invention Sectional view of an inductor in one embodiment of the present invention A diagram of a coil in one embodiment of the present invention

An inductor according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective perspective view of an inductor in one embodiment of the present invention, and FIG. 2 is a cross-sectional view of a surface including the coil center axis L0 in FIG. is.

The molded body 12 is made of a composite magnetic material containing magnetic powder and a binder material. An alloy of Fe, Si, Cr, and B is used as the magnetic powder, and a silicon resin is used as the binder material. be done. The size of the compact is 2.5 mm in width, 2.0 mm in depth, and 1.2 mm in thickness. A coil 11 is embedded inside the compact.

The coil 11 is made of a plate-shaped copper wire, and the surface thereof is coated with an insulating film by electrodeposition. The average thickness of this insulating coating is about 5 μm, and the thickness of the corner portions is about 2 μm. The conductive wire has a thickness of 0.05 mm and a width of 0.30 mm. The conductive wire is wound in two stages by flatwise winding such that the width direction of the conductive wire is parallel to the winding axis of the coil 11 . The coil 11 is wound in an elliptical shape with a major axis of 1.9 mm and a minor axis of 1.6 mm. A coating layer 18 made of polyimide is further provided on the coil 11 . The average thickness of the outer peripheral surface of the coil winding portion of the coating layer 18 is about 5.8 μm, and the minimum thickness (T in FIG. 2) of the corner portion of the coil winding portion is about 3.1 μm. By applying such a highly insulating coating layer 18 to the coil 11 , the insulating properties of the coil 11 can be improved, and short circuits due to voltage generated between the external electrode 15 and the coil 11 can be prevented. When a coating layer is formed by the normal dipping method, if the viscosity of the coating liquid is high, the film thickness tends to be excessive and the inductance value tends to deteriorate. There is a possibility that there will be a part that does not adhere at all to the corner. Conductive wire ends 13 are drawn out along the outer periphery of coil 11 and connected to external electrodes 15 formed on both end surfaces of molded body 12 .

External electrodes 15 are formed on both end surfaces of the compact 12 . The external electrodes 15 are obtained by applying a conductive paste material made by mixing silver powder and resin to both end surfaces of the molded body 12 and curing the material, and the thickness thereof is about 0.05 to 0.1 mm. is. This conductor wire is covered with an insulating coating, but by cutting it at the cut surface 17 , the copper is exposed, so that it can be electrically connected to the external electrode 15 . The surface of the external electrode 15 is plated with nickel and tin so that it can be mounted by soldering.

In addition, the conductor end 13 is arranged at the boundary between the upper and lower stages of the coil 11, and the fillet portion of the coating layer 18 is formed at the angle between the conductor end 13 and the wall surface of the winding portion of the coil 11, and the thickness of the fillet portion is the same as that of the coil. It is about three times the average thickness of the coating layer 15 on the outer periphery.

Here, the definition of the thickness of the fillet portion will be explained. In FIG. 2, the intersection of the side L1 on the surface of the conductor end portion 13 and the side L2 on the outer peripheral surface of the winding portion of the coil is P, and the shortest distance X from P to the surface of the coating layer 18 is the thickness of the fillet portion. and

The sectional view of FIG. 2 is perpendicular to the lead-out direction of the conductor end 13 and is taken through a portion where the conductor end 13 and the winding portion of the coil 11 are closest to each other.

By forming the fillet portion with the thickness described above, it is possible to suppress deformation of the coil 11 in the forming process of the formed body 12, and to manufacture a high-quality inductor with little change in inductance value.

It is desirable that the minimum thickness of the corners of the winding portion of the coil 11 of the coating layer 18 is 25% or more of the average thickness of the outer peripheral surface of the winding portion of the coil 11 of the coating layer 18 . If the minimum thickness of the corners is less than 25% of the average thickness, sufficient voltage resistance cannot be ensured.

Moreover, it is desirable that the average thickness of the outer peripheral surface of the winding portion of the coil 11 of the coating layer 18 is 1 μm or more and 20 μm or less. If the average thickness of the outer peripheral surface is less than 1 μm, sufficient voltage resistance cannot be ensured. If the average thickness of the outer peripheral surface is thicker than 20 μm, a sufficient inductance value cannot be secured.

Furthermore, the fillet portion of the coating layer 18 is formed at the angle formed by the wire end portion 13 of the flat wire and the wall surface of the winding portion, and the thickness of the fillet portion is the minimum thickness of the corner portion of the winding portion of the coil 11 of the coating layer 18. It is desirable that the thickness be two times or more and ten times or less. When the thickness of the fillet portion is less than twice the minimum thickness of the corner portions of the winding portion, it becomes difficult to sufficiently suppress the deformation of the coil during the forming process. If the thickness of the fillet portion is more than 10 times the minimum thickness of the corner portion of the winding portion, a sufficient inductance value cannot be secured.

Next, the manufacturing method of the inductor of this invention is demonstrated.

First, the kneading process is performed. A magnetic powder and a binder material are kneaded to form a slurry. An alloy of Fe, Si, Cr, and B is used as the magnetic powder, and silicon resin is used as the binder material.

Next, a sheet forming process is performed. The slurry is poured onto a flat substrate into a sheet and allowed to dry. A magnetic sheet is thus formed. After the magnetic sheet is dried, it is cut into appropriate sizes.

On the other hand, the conducting wire is wound by a winding machine to form a coil. As the conducting wire, a plate-shaped copper conducting wire with an insulating coating applied to the surface thereof is used. The conductive wire is wound in two stages by flatwise winding such that the width direction of the conductive wire is parallel to the winding axis of the coil. At this time, the conductor wire is wound so that the lead-out portion of the conductor wire is located on the outer circumference of the winding portion. Also, the two lead-out portions are led out in opposite directions from the outer periphery of the winding portion. Furthermore, the conductor wire is twisted and bent so that the lead-out direction of the conductor wire ends is parallel to the minor axis direction of the coil and the width direction of the conductor wire ends is parallel to the major axis direction of the coil. applied.

After processing the wire ends, the coil is fixed on a fixed frame made of stainless steel. FIG. 3 is a diagram of a coil and fixed frame in one embodiment of the present invention. The fixed frame 14 in FIG. 3 is a plate with a thickness of 0.1 mm and has a grid shape, and about nine coils 11 are joined on the grid of the fixed frame 14 . Place the coil terminal on the grid and fix the terminal and grid with adhesive. A thermosetting epoxy adhesive is used as the adhesive.

Next, a coil coating process is performed. A coating agent is applied to the stationary frame 14 and the plurality of coils 11 by an electrostatic applicator to form a coating layer 18 on the surface of the coils. Polyimide resin is used as the coating agent.

Next, a laminate molding press process is performed. Magnetic sheets are laminated on the upper and lower sides of the fixed frame 14 to which the coil 11 is adhered, and press molding is performed by applying heat and load. The temperature during press molding is about 120 to 180° C., and heat increases the fluidity of the magnetic sheet. The gap around the coil is filled by deformation and press-fitting of the magnetic sheet, and the magnetic sheet adheres, hardens, and integrates. A fixed frame, to which a plurality of coils are joined through such a process, is embedded inside the magnetic sheet.

Next, a heat curing process is performed. The magnetic sheet molded by hot pressing is completely hardened by a heat curing process at 180° C. for 2 hours to secure the required strength as a molded body.

Next, a singulation process is performed. The magnetic sheet is cut by a dicing machine, and individualized into compacts each including individual coils. At this time, the cut surface 17 is cut so as to pass over the conductor end portion 13 , thereby exposing the cut surface 17 of the coil terminal to the end surface of the molded body 12 . Also, the fixed frame 14 is completely removed by dicing so that it does not remain inside the compact 12 .

Finally, an electrode forming process is performed. A conductive paste material is applied to the end faces of the individualized molded bodies 11, and dried and cured by heating. After that, the surface of the conductive paste material is plated to form external electrodes 15, completing the inductor. In the electrode forming step, since the cut surface 17 of the conductor end 13 is exposed on the end surface of the molded body, the conductor end 13 is electrically joined to the external electrode 15 at the cut surface.

Next, the coil coating process will be described in more detail.

Common coating methods that have been used in the past include the dipping method, in which the object is immersed in liquid, and the injection spraying method, in which the object is sprayed with liquid atomized by an injection spray. If the viscosity of the liquid is high, the film thickness tends to be excessive. It is difficult to control the entire surface of the object to have a uniform film thickness of about 1 to 20 μm.

In the injection spray method, since it is difficult to spray a coating liquid with high viscosity, it is necessary to reduce the viscosity of the coating liquid.

Therefore, in the coil of the present invention using a flat conductor wire, the above-mentioned dipping method and injection spray method are not suitable in consideration of ensuring the coating layer on the corners of the flat wire.

Therefore, in the method of manufacturing an inductor according to the present invention, the surface of the coil is coated by an electrostatic coating method capable of generating an atomized spray even with a highly viscous coating liquid.

FIG. 4 is a drawing of the coating process in the coil coating process. Coil 11 and fixed frame 14 are placed on metal fixture 16 . The fixing frame 14 and the fixing jig 16 are fixed with a polyimide adhesive tape. The fixture 16 is tilted at an angle of 45° with respect to the horizontal. Further, the fixing jig 16 is grounded so as to have a potential of 0V. Further, the fixing jig 16 is heated by a heater and kept at 80 to 100.degree.

A nozzle 19 for supplying the coating liquid 21 is installed above the fixing jig 16, the coil 11, and the fixing frame 14 which are held in the above state. A voltage is applied to the nozzle 19 so as to have a potential of about 10 kV. The coating liquid 21 is ejected from such nozzles 19 . The coating liquid 21 is a mixture of polyimide resin and solvent, and N-methylpyrrolidone is used as the solvent. The amount of solvent is adjusted so that the coating liquid 21 has a viscosity of about 1 to 5 Pa·s. By using the coating liquid 21 having such a viscosity, the thickness of the coating layer 18 formed at the corners of the coil 11 can be ensured.

Since the coating liquid 21 ejected from the nozzle 19 is positively charged, the electrostatic repulsive force causes the liquid to gradually disperse into fine particles as it falls from the nozzle 19 . Due to the effect of such static electricity, even a highly viscous coating liquid can be made into fine particles.

Since the upper surface of the coil 11 is inclined at 45° with respect to the horizontal, the coating liquid 21 falling from above is applied to the upper surface, the outer peripheral surface, and the corners of the coil 11, respectively. Since the coating liquid 21 is atomized, the coating liquid 21 applied to each part forms a uniform coating layer 18 with no unevenness on the surface of each part. A fillet portion is formed between the wire end portion 13 of the coil 11 and the outer peripheral surface. Further, since the fixing jig 16 is heated to 80° C. or higher, the coil 11 is also heated by heat transfer from the fixing jig 16 . When the coating liquid 21 adheres to the surface of the coil 11, the solvent contained in the coating liquid 21 evaporates due to the heat, and the polyimide resin contained in the coating liquid 21 increases in concentration and viscosity. The coating liquid 21 is less likely to flow down from the corners, and the thickness of the corners is ensured.

In order to uniformly apply the coating liquid to the entire fixed frame 14, the nozzle 19 applies the coating liquid 21 while moving the upper portion of the fixed frame 14 at a constant speed.

After completing the coating of the front surface of the fixed frame 14, the fixed frame 14 is removed from the fixing jig 16, inverted and fixed to the fixing jig 16 again, and the back surface of the fixed frame 14 is coated.

After completing the coating on the back surface of the fixed frame 14, the fixed frame 14 and the fixing jig 16 are placed in a heating furnace and dried at 120° C. for 30 minutes. After that, it is heated at 200° C. for 1 hour or longer. A heating process at 200° C. completely cures the polyimide resin in the coating layer 18 . When the heating is completed, the fixing frame 14 is removed from the fixing jig, and the coil coating process is completed.

As for the film thickness of the coating layer 18 obtained by the above process, the average film thickness of the outer peripheral portion of the coil 11 is 5.8 μm, the minimum thickness of the corner portion is 3.1 μm, and the minimum thickness of the corner portion is the average thickness of the outer peripheral portion. It is about 59%.

Note that the above film thickness measurement locations will be described with reference to FIGS. 5 and 6. FIG. FIG. 5 shows only the coil 11 and the coating layer 18 extracted from FIG. FIG. 6 is a view of the coil 11 viewed from above in the axial direction. Film thickness measurement points are shown as black circles in FIGS. As shown in FIGS. 5 and 6, the minimum thickness of the coil corners is obtained by measuring the coating layer thickness at 8 points on the circumference of the outer diameter of the coil and 8 points on the circumference of the inner diameter of the coil, for a total of 16 points. I took the one with the smallest value. The thickness of the outer circumference of the coil was obtained by taking the average value of a total of 8 points of the thickness of the coating layer formed on the surface of the central part in the longitudinal direction of the conductor, 4 points in the circumferential direction at each of the upper and lower stages.

Also, the coating layer formed in this step is made of polyimide resin. Resins that are commonly used as coating resins include polyimide resins as well as epoxy resins and silicone resins. The glass transition point of the resin is 220° C. or higher, which is a relatively high temperature. Therefore, the coating layer can maintain sufficient hardness even in the high-temperature molding process at 120 to 180° C. in the lamination press process, which is a post-coil coating process, so that the insulating film of the coil 11 can be protected. can be done. In addition, since polyimide resin has a higher withstand voltage than epoxy resin or silicone resin, the withstand voltage of the inductor can be further increased.

INDUSTRIAL APPLICABILITY The inductor and the manufacturing method thereof according to the present invention can obtain an inductor having high inductance and excellent current resistance and voltage resistance, and is industrially useful.

REFERENCE SIGNS LIST 11 coil 12 molded body 13 wire end 14 fixing frame 15 external electrode 16 fixing jig 17 cut surface 18 coating layer 19 nozzle 21 coating liquid

Claims (5)

An inductor comprising a coil wound with an insulating coated flat conductor wire and a composite magnetic material containing a metal magnetic powder and a binder material embedded in the coil, wherein the wound part of the coil and the composite magnetic material A coating layer is provided between them, and the minimum thickness of the corners of the winding portion of the coil of the coating layer is 25% or more of the average thickness of the outer peripheral surface of the winding portion of the coil of the coating layer. inductor. 2. The inductor according to claim 1, wherein the coating layer has an average thickness of 1 [mu]m or more and 20 [mu]m or less on the outer peripheral surface of the winding portion of the coil. 2. The inductor according to claim 1, wherein a polyimide film is used for said coating layer. The coil is wound flatwise in two stages, upper and lower, and a fillet portion of the coating layer is formed at an angle formed by an end portion of the flat conductor wire and a wall surface of the winding portion. 2. The inductor according to claim 1, wherein the thickness of the coating layer is two times or more and ten times or less the minimum thickness of the corner portions of the coil winding portions of the coating layer. A step of mixing metal magnetic powder and a binder material to form a magnetic sheet, a step of winding an insulating-coated rectangular conducting wire to form a coil, a step of forming a coating layer on the surface of the coil, and the coating. A method for manufacturing an inductor, comprising the step of sandwiching the coil formed with layers between the magnetic sheets, pressing them, and heat-curing them, wherein the step of forming the coating layer includes electrostatically applying a coating resin. By forming the coating layer by, the minimum thickness of the corners of the winding portion of the coil of the coating layer is 25% or more of the average thickness of the outer peripheral surface of the winding portion of the coil of the coating layer. manufacturing method of inductor.

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