JP7352155B2 - Core, inductor parts and core manufacturing method - Google Patents

Description

The present invention relates to a core, an inductor component, and a method for manufacturing the core.

Conventionally, as an inductor component, there is one described in Utility Model Application Publication No. 4-67309 (Patent Document 1). This inductor component includes an annular core and a coil wound around the core.

Utility Model Publication No. 4-67309

By the way, in the conventional inductor component, the core includes a core body and an insulating film covering the core body. Usually, the insulating film is formed by applying a resin material to the core body and drying and curing the resin material.

The core body has an outer circumferential surface, an inner circumferential surface, and first and second end surfaces facing each other in the direction of the central axis of the core body. A corner portion is provided between the outer circumferential surface and the inner circumferential surface and the first end surface and the second end surface.

When applying the resin material to the core body, the resin material is difficult to stay at the corners of the core body, so the thickness of the insulating film at the corners that cover the corners of the core body becomes thinner. There is a risk.

Therefore, if the coil wound around the core comes into contact with a corner of the insulating film, the corner of the insulating film may be chipped and the corner of the core body may be exposed. As a result, if the core body is conductive, there is a risk that the coil and the core body may become energized, whereas if the core body is not conductive, the coil may come into contact with the corner of the core body. This may cause the coil to wear out.

SUMMARY OF THE INVENTION Therefore, an object of the present disclosure is to provide a core that can reduce chipping at the corners of an insulating film, an inductor component having the core, and a method for manufacturing the core.

In order to solve the above problem, a core that is an aspect of the present disclosure includes:
an annular core body;
an insulating film covering the core body,
The core main body has a first side surface on the outside in the radial direction, a second side surface on the inside in the radial direction, a first end surface and a second end surface facing each other in the central axis direction of the core main body, and the first side surface and the second side surface. a first corner provided between first end surfaces; a second corner provided between the first side surface and the second end surface; and a second corner provided between the second side surface and the first end surface. and a fourth corner provided between the second side surface and the second end surface,
The insulating film includes a first corner portion that covers the first corner portion, a second corner portion that covers the second corner portion, a third corner portion that covers the third corner portion, and a fourth corner portion. a fourth corner portion that covers, a first center portion that covers a first center portion located at the center in the center axis direction of the core body portion on the first side surface, and a first center portion that covers the first center portion located at the center in the center axis direction of the core body portion on the second side surface; a second central portion covering a second central portion located at the center of the second central portion;
At least one thickness of each of the first to fourth corner portions is thicker than at least one thickness of each of the first and second central portions.

According to the above aspect, when manufacturing an inductor component by winding a coil around a core, even if the coil comes into contact with a corner part of the insulating film, the thickness of the corner part of the insulating film is smaller than the thickness of the central part of the insulating film. Since the insulating film is also thick, chipping at the corners of the insulating film can be reduced. This reduces the exposure of the corners of the core body, and reduces the current flow between the coil and the core body when the core body has conductivity, whereas when the core body has no conductivity, It is possible to reduce wear on the coil due to the coil coming into contact with the corner of the core body.

In one embodiment of the core, the insulating film includes a resin layer that covers at least the first side surface and the second side surface of the core body, and a resin layer that covers at least the first end surface and the second end surface of the core body. and a resin sheet covering at least one surface.

According to the embodiment, the insulation of the core can be ensured by providing the resin layer and the resin sheet with an insulation function. By imparting a flatness function to the resin sheet, at least one of the first end surface and the second end surface of the core can be made flat, and it is possible to prevent the coil from being irregularly wound when the coil is wound around the core.

In one embodiment of the core, the insulating film is composed of two layers: the resin layer that contacts the core body and the resin sheet that contacts the resin layer.

According to the embodiment, since the insulating film is composed of two layers, sufficient insulation can be ensured on at least one of the first end surface and the second end surface of the core.

In one embodiment of the core, the insulating film is composed of one layer of the resin sheet that contacts the core body.

According to the embodiment, since the insulating film is composed of one layer, the dimension of the core in the central axis direction can be reduced.

In one embodiment of the core, at least one of the first to fourth corner portions of the insulating film includes an inclined surface provided on the resin layer.

Moreover, in one embodiment of the core, at least one of the first to fourth corner portions of the insulating film includes a convex surface provided on the resin sheet.

Additionally, in one embodiment of the inductor component,
The core;
and a coil wound around the core.

According to the embodiment, it is possible to realize an inductor component having a core that can reduce chipping at the corner portions of the insulating film.

Further, in one embodiment of the inductor component, the coil is formed by connecting a plurality of pin members.

According to the embodiment, since the coil is composed of a plurality of pin members, the rigidity of the coil is increased, but chipping of the corner portions of the insulating film can be reduced.

Further, in one embodiment of the method for manufacturing the core,
a step of applying a resin layer to the first side surface, the second side surface and the first end surface of the core body;
a step of preparing a resin sheet;
placing the first end surface side of the core body portion on the resin sheet.

According to the embodiment, by forming the resin layer and the resin sheet on the core body, the core body can be covered with the insulating film made of the resin layer and the resin sheet. Thereby, the corner between the first end surface and the first and second side surfaces of the core body can be reliably covered with the insulating film. Therefore, when manufacturing an inductor component by winding a coil around a core, even if the coil contacts a corner portion of the insulating film, chipping of the corner portion of the insulating film can be reduced.

Furthermore, the resin layer applied to the side surface of the core body drips down to the first end surface side of the core body due to gravity. As a result, the thickness of the resin layer becomes thicker toward the first end surface of the core body. Therefore, the thickness of the resin layer covering the corners of the core body can be increased. Furthermore, since the first end surface side of the core body is covered with the resin sheet, the corners of the core body can also be covered with the resin sheet.

Further, in one embodiment of the core manufacturing method, in the step of placing the core body on the resin sheet, the core body is pressed against the resin sheet.

According to the embodiment, since the core body is pressed against the resin sheet, the resin sheet can bulge at the corner of the core body and cover the corner of the core body.

According to the core, inductor component, and core manufacturing method that are one aspect of the present disclosure, chipping at the corner portions of the insulating film can be reduced.

FIG. 1 is a top perspective view showing an inductor component according to an embodiment of the present invention. FIG. 3 is a bottom perspective view of the inductor component. FIG. 3 is a top perspective view showing the inside of the inductor component. FIG. 3 is an exploded perspective view of an inductor component. FIG. 3 is a plan view of an inductor component. FIG. 3 is a cross-sectional view of an inductor component. FIG. 3 is a cross-sectional view of the core. FIG. 3 is an enlarged cross-sectional view of the core. It is an explanatory view explaining a manufacturing method of a core. It is an explanatory view explaining a manufacturing method of a core. It is an explanatory view explaining a manufacturing method of a core. It is an explanatory view explaining a manufacturing method of a core. It is an explanatory view explaining a manufacturing method of a core. It is a top view of a mask. It is an enlarged image diagram of the core. FIG. 7 is an enlarged cross-sectional view of the core of the second embodiment. FIG. 7 is an enlarged cross-sectional view of the core of the third embodiment. It is an explanatory view explaining another method of manufacturing the core of a 1st embodiment. It is an explanatory view explaining a state when a bending pin member of a coil is wound around a core.

Hereinafter, an inductor component that is one aspect of the present disclosure will be described in detail with reference to illustrated embodiments. Note that some of the drawings are schematic and may not reflect actual dimensions and proportions.

(First embodiment)
(Configuration of inductor parts)
FIG. 1 is a top perspective view showing an inductor component 1 according to an embodiment of the present invention. FIG. 2 is a bottom perspective view of the inductor component 1. FIG. 3 is a top perspective view showing the inside of the inductor component 1. FIG. FIG. 4 is an exploded perspective view of the inductor component 1.

As shown in FIGS. 1 to 4, the inductor component 1 includes a case 2, an annular core 3 housed in the case 2, a first coil 41 and a second coil 42 wound around the core 3, It has first to fourth electrode terminals 51 to 54 attached to the case 2 and connected to the first coil 41 and the second coil 42. Inductor component 1 is a common mode choke coil.

The case 2 includes a bottom plate part 21 and a box-shaped lid part 22 that covers the bottom plate part 21. The case 2 is made of a flame-retardant material, for example, a resin such as polyphenylene sulfide resin (PPS) or polyphthalamide resin (PPA), or ceramics. The core 3 is installed on the bottom plate portion 21 so that the central axes of the core 3 are perpendicular to each other. The central axis of the core 3 refers to the central axis of the inner diameter hole of the core 3. The shape of the case 2 (the bottom plate part 21 and the lid part 22) is rectangular when viewed from the central axis direction of the core 3. In this embodiment, the shape of case 2 is rectangular. Here, the lateral direction of the case 2 is defined as the X direction, the longitudinal direction of the case 2 is defined as the Y direction, and the height direction of the case 2 is defined as the Z direction.

The first to fourth electrode terminals 51 to 54 are attached to the bottom plate portion 21. The first electrode terminal 51 and the second electrode terminal 52 are located at two corners of the bottom plate portion 21 facing each other in the Y direction, and the third electrode terminal 53 and the fourth electrode terminal 54 are located at two corners of the bottom plate portion 21 facing each other in the Y direction. It is located in two corners. The first electrode terminal 51 and the third electrode terminal 53 face each other in the X direction, and the second electrode terminal 52 and the fourth electrode terminal 54 face each other in the X direction.

The shape of the core 3 (that is, the shape of the inner circumferential surface and the outer circumferential surface of the core 3) is an ellipse (track shape) when viewed from the central axis direction. When viewed from the central axis direction, the core 3 includes a pair of longitudinal parts 31 extending along the long axis and opposing each other in the short axis direction, and a pair of short parts 31 extending along the short axis and opposing each other in the long axis direction. 32. Note that the shape of the core 3 may be rectangular or elliptical.

The core 3 is composed of, for example, a ceramic core such as ferrite, or a metal core. The core 3 has two end faces facing each other in the central axis direction. The first end surface (bottom surface) faces the inner surface of the bottom plate portion 21 . The second end surface (upper surface) faces the inner surface of the lid portion 22. The core 3 is housed in the case 2 so that the long axis direction of the core 3 coincides with the Y direction.

The first coil 41 is wound around the core 3 between the first electrode terminal 51 and the second electrode terminal 52. One end of the first coil 41 is connected to the first electrode terminal 51. The other end of the first coil 41 is connected to a second electrode terminal 52.

The second coil 42 is wound around the core 3 between the third electrode terminal 53 and the fourth electrode terminal 54 . One end of the second coil 42 is connected to a third electrode terminal 53. The other end of the second coil 42 is connected to a fourth electrode terminal 54.

The first coil 41 and the second coil 42 are wound along the long axis direction of the core 3 so as to face each other in the short axis direction. That is, the first coil 41 is wound around one longitudinal portion 31 of the core 3 , and the second coil 42 is wound around the other longitudinal portion 31 of the core 3 . The winding axis of the first coil 41 and the winding axis of the second coil 42 run in parallel. The first coil 41 and the second coil 42 are symmetrical with respect to the long axis of the core 3.

The number of turns of the first coil 41 and the number of turns of the second coil 42 are the same. The winding direction of the first coil 41 around the core 3 and the winding direction of the second coil 42 around the core 3 are opposite directions. In other words, the winding direction of the first coil 41 from the first electrode terminal 51 to the second electrode terminal 52 is opposite to the winding direction of the second coil 42 from the third electrode terminal 53 to the fourth electrode terminal 54. direction.

The common mode current flows from the first electrode terminal 51 to the second electrode terminal 52 in the first coil 41 and from the third electrode terminal 53 to the fourth electrode terminal 54 in the second coil 42 . When a common mode current flows through the first coil 41, a first magnetic flux is generated by the first coil 41 in the core 3. When a common mode current flows through the second coil 42, a second magnetic flux is generated in the core 3 in the same direction as the first magnetic flux. Therefore, the first coil 41 and core 3 and the second coil 42 and core 3 act as inductance components, and common mode component noise is removed.

The first coil 41 is formed by connecting a plurality of pin members by, for example, laser welding, spot welding, soldering, or the like. The plurality of pin members are not printed wiring or conductive wires, but are rod-shaped members. The pin member has rigidity and is more difficult to bend than the conductive wire.

The plurality of pin members include a bent pin member 410 that is bent into a substantially U-shape, and linear pin members 411 and 412 that extend substantially linearly. The first coil 41 includes, in order from one end to the other end, a first straight pin member 411, a plurality of sets of bent pin members 410 and a second straight pin member 412, and a first straight pin member 411. The lengths of the first linear pin member 411 and the second linear pin member 412 are different.

The bent pin members 410 and the second straight pin members 412 are alternately connected by, for example, laser welding, spot welding, soldering, or the like. One end of a second straight pin member 412 is connected to one end of the bending pin member 410, and the other end of the second straight pin member 412 is connected to one end of another bending pin member 410. By repeating this, the plurality of bent pin members 410 and the second straight pin members 412 are wound helically around the core 3. In other words, one set of bent pin member 410 and second straight pin member 412 constitutes a unit element of one turn.

The first electrode terminal 51 is connected to one first straight pin member 411, and this first straight pin member 411 is connected to one end of a bent pin member 410 adjacent to this first straight pin member. The second electrode terminal 52 is connected to the other first straight pin member 411, and this first straight pin member 411 is connected to one end of a second straight pin member 412 adjacent to this first straight pin member 411. .

The second coil 42, like the first coil 41, is composed of a plurality of pin members. That is, the second coil 42 includes, in order from one end to the other end, a first straight pin member 421, a plurality of sets of bent pin members 420 and a second straight pin member 422, and a first straight pin member 421. Bent pin members 420 and second straight pin members 422 are alternately connected and wound around the core 3 .

The third electrode terminal 53 is connected to one first straight pin member 421, and this first straight pin member 421 is connected to one end of a bent pin member 420 adjacent to this first straight pin member 421. The fourth electrode terminal 54 is connected to the other first straight pin member 421, and this first straight pin member 421 is connected to one end of a second straight pin member 422 adjacent to this first straight pin member 421. .

FIG. 5 is a plan view of the inductor component 1. FIG. 6 is an XZ cross-sectional view passing through the center of the inductor component 1 in the Y direction. As shown in FIGS. 5 and 6, the first coil 41 and the second coil 42 (pin members 410 to 412, 420 to 422) each include a conductor portion and a coating covering the conductor portion. The conductor portion is, for example, a copper wire, and the coating is, for example, a polyamide-imide resin. The thickness of the coating is, for example, 0.02 to 0.04 mm.

Specifically, the first linear pin members 411, 421 are composed of conductor portions 411a, 421a without a coating. The second straight pin members 412, 422 are composed of conductor portions 412a, 422a without a coating. The bending pin members 410, 420 are composed of conductor portions 410a, 420a and coatings 410b, 420b.

At one end and the other end of the bending pin members 410, 420, the conductor portions 410a, 420a are exposed from the coatings 410b, 420b. That is, the first straight pin members 411, 421, the second straight pin members 412, 422, and the bent pin members 410, 420 are joined to each other at the exposed conductor parts 411a, 421a, 412a, 422a, 410a, 420a. has been done. After the pin members 410 to 412 and 420 to 422 are joined, the uncoated portions of the pin members 410 to 412 and 420 to 422 (including the joined portions) are covered with a coating material. The coating material is, for example, polyamideimide resin. Note that the coating material may be attached to a portion of the coatings 410b, 420b of the pin members 410, 420.

The inductor component 1 further includes an insulating resin body 60 that covers a portion of the first coil 41 and a portion of the second coil 42. As the material of the insulating resin body 60, for example, thermosetting epoxy resin can be used. Specifically, the insulating resin body 60 includes at least some of the conductor parts 411a, 412a, 410a exposed from the insulating film in the first coil 41, and conductor parts 421a, 422a, exposed from the insulating film in the second coil 42. Covers at least a portion of 420a.

The core 3 includes a core body 300 made of ferrite or the like, and an insulating film 310 made of resin or the like that covers the core body 300. The core body portion 300 may have electrical conductivity depending on the ferrite material. Even in this case, the insulating film 310 prevents electrical conduction between the first and second coils 41 and 42 and the core body portion 300. On the other hand, when the core body part 300 does not have electrical conductivity, the insulating film 310 reduces wear on the coils 41 and 42 due to the coils 41 and 42 coming into contact with the core body part 300.

FIG. 7 is a cross-sectional view of the core 3 perpendicular to the circumferential direction. As shown in FIG. 7, the core body 300 has a first side surface 301 as an outer peripheral surface on the radially outer side, a second side surface 302 as an inner peripheral surface on the radially inner side, and a central axis direction of the core body 300. It has a first end surface 303 and a second end surface 304 facing each other in the Z direction. The first end surface 303 becomes the bottom surface on the bottom plate portion 21 side when the core 3 is housed in the case 2. The second end surface 304 becomes the upper surface when the core 3 is housed in the case 2.

A first corner 305a is provided between the first side surface 301 and the first end surface 303, a second corner 305b is provided between the first side surface 301 and the second end surface 304, and a second corner 305b is provided between the first side surface 301 and the second end surface 304. A third corner 305c is provided between and the first end surface 303, and a fourth corner 305d is provided between the second side surface 302 and the second end surface 304. The first to fourth corners 305a to 305d are convex curved surfaces. Specifically, in a cross section perpendicular to the circumferential direction of the core body portion 300, the first to fourth corners 305a to 305d refer to the entire convex curved surface. Note that the shape of at least one of the first to fourth corners 305a to 305d may be an inclined surface or a ridgeline such as a straight line or a curved line.

The insulating film 310 is made of a resin material such as polyurethane resin, epoxy resin, or vinyl resin, for example. The insulating film 310 has corner parts 310a to 310d that cover the corners 305a to 305d of the core body part 300, and a central part that covers the central parts 301a and 302a located at the center of the core body part 300 in the central axis direction (Z direction). 310e and 310f.

The first corner portion 310a covers the first corner portion 305a, the second corner portion 310b covers the second corner portion 305b, the third corner portion 310c covers the third corner portion 305c, and the fourth corner portion 310d covers the fourth corner 305d. The first central portion 310e covers the first central portion 301a, and the second central portion 310f covers the second central portion 302a. The first center portion 301a is located at the center of the core body portion 300 on the first side surface 301 in the Z direction, and the second center portion 302a is located at the center of the core body portion 300 on the second side surface 302 in the Z direction.

Each of the first to fourth corner portions 310a to 310d is thicker than each of the first and second central portions 310e and 310f. The thickness refers to the thickness in the direction perpendicular to the surface of the core body portion 300. Specifically, the thickness t1 of the first central portion 310e refers to the thickness in the direction perpendicular to the surface of the first central portion 301a. The thickness T1 of the first corner portion 310a refers to the average thickness in the direction perpendicular to the surface of the first corner portion 305a. In FIG. 7, the thickness T1 of the first corner portion 310a indicates the maximum thickness for ease of understanding. Note that the thickness of at least one of the first to fourth corner portions 310a to 310d only needs to be thicker than the thickness of at least one of the first and second central portions 310e and 310f.

According to this, when manufacturing the inductor component 1 by winding the coils 41 and 42 around the core 3, even if the coils 41 and 42 contact the corner portions 310a to 310d of the insulating film 310, the corner portions of the insulating film 310 Since the thicknesses 310a to 310d are thicker than the thicknesses of the central portions 310e and 310f of the insulating film 310, chipping of the corner portions 310a to 310d of the insulating film 310 can be reduced. Thereby, exposure of the corners 305a to 305d of the core body 300 is reduced, and when the core body 300 has conductivity, current flow between the coils 41, 42 and the core body 300 is reduced. When the coils 300 are not conductive, wear of the coils 41, 42 due to contact with the corners 305a to 305d of the core body 300 can be reduced.

FIG. 8 is an enlarged sectional view of the core 3. As shown in FIGS. 7 and 8, the insulating film 310 includes a resin layer 311 that covers at least side surfaces 301 and 302 of the core body 300 and at least one of the first end surface 303 and the second end surface 304 of the core body 300. and a resin sheet 312 that covers the surface. In this embodiment, the resin layer 311 covers the entire surface of the core body section 300, and the resin sheet 312 covers the first end surface 303 and the second end surface 304 of the core body section 300. Note that in this embodiment, a boundary exists between the resin layer 311 and the resin sheet 312, but the resin layer 311 and the resin sheet 312 are integrated by the material and there is no clear boundary. Good too.

According to this, the insulating properties of the core 3 can be ensured by providing the resin layer 311 and the resin sheet 312 with an insulating function. By giving the resin sheet 312 a flatness function, the first end surface and the second end surface of the core 3 can be made flat, and when the coils 41 and 42 are wound around the core 3, winding disorder of the coils 41 and 42 can be prevented. It can be prevented. In particular, when the coils 41 and 42 are composed of a plurality of pin members, the pin members cannot take a shape that conforms to the unevenness and are easily affected, but the first end surface and the second end surface of the core 3 Since it is flat, there are no such problems.

On at least one of the first end surface 303 and the second end surface 304 of the core body section 300, the insulating film 310 has two layers: a resin layer 311 in contact with the core body section 300 and a resin sheet 312 in contact with the resin layer 311. It consists of In this embodiment, on the first end surface 303 and the second end surface 304 of the core body part 300, the insulating film 310 has two layers: a resin layer 311 in contact with the core body part 300 and a resin sheet 312 in contact with the resin layer 311. It consists of

According to this, since the insulating film 310 is composed of two layers on the first end surface 303 and the second end surface 304 of the core body part 300, the insulation film 310 has sufficient insulation properties on the first end surface and the second end surface of the core 3. Can be secured. The width of the resin sheet 312 is preferably larger than the width of the core body part 300, and in addition to the resin layer 311, the resin sheet 312 can also cover the corner part 305a of the core body part 300, and the width of the insulating film 310. The thickness of the corner portion 310a can be increased.

The first corner portion 310a of the insulating film 310 includes an inclined surface 311a provided on the resin layer 311. The inclined surface 311a is formed such that the thickness of the resin layer 311 becomes continuously thicker toward both ends in the Z direction (lower side in FIG. 8). According to this, the thickness of the first corner portion 310a can be increased with a simple configuration. At least one of the first to fourth corner portions 310a to 310d may include the inclined surface 311a. Note that the periphery of the first corner portion 310a of the insulating film 310 may include a concave surface. The concave surface is formed such that the thickness of the resin layer 311 becomes continuously thicker toward both ends in the Z direction (lower side in FIG. 8).

According to the inductor component 1, since it has the core 3, even if the coils 41 and 42 contact the corner portions 310a to 310d of the insulating film 310, the thickness of the corner portions 310a to 310d of the insulating film 310 is smaller than that of the insulating film. Since it is thicker than the central portions 310e and 310f of the insulating film 310, chipping of the corner portions 310a to 310d of the insulating film 310 can be reduced. Thereby, exposure of the corners 305a to 305d of the core body 300 can be reduced, and energization between the coils 41, 42 and the core body 300 can be reduced.

Furthermore, since the coils 41 and 42 are composed of a plurality of pin members, the rigidity of the coils 41 and 42 is increased. Therefore, when the coils 41, 42 come into contact with the corners 305a to 305d of the core body 300, the pin members are difficult to bend and absorb the impact between the coils 41, 42 and the core body 300, and the pin members are worn out. There is a risk. However, since chipping of the corner portions 310a to 310d of the insulating film 310 can be reduced, exposure of the corner portions 305a to 305d of the core body portion 300 can be reduced, and wear of the coils 41 and 42 can be reduced.

(Core manufacturing method)
Next, a method for manufacturing the core 3 will be explained.

FIG. 9A shows a step of applying a resin layer 311 to the side surfaces 301 and 302 and the first end surface 303 of the core body portion 300. As shown in FIG. 9A, the core body 300 is immersed in the resin bath 70 with the first end surface 303 of the core body 300 facing downward. The resin tank 70 contains a liquid first resin 71. The first resin 71 is a thermosetting resin. The resin tank 70 is placed on a heating device 80 such as a hot plate.

Then, as shown in FIG. 9B, the core body part 300 is pulled up from the resin bath 70, and a resin layer 311 is applied to the side surfaces 301, 302 and the first end face 303 of the core body part 304. The excess resin layer 311 attached to the core body portion 300 may be removed by the etching plate 75. At this time, the state of the resin layer 311 is "undried".

Here, the state of the resin is "undried" in the applied state, "dried (uncured)" in the state in which only the solvent is volatilized by heating below the resin curing temperature, and "dry (uncured)" in the state heated below the resin curing temperature. There is a "hardened" state.

FIG. 9C shows the process of preparing the resin sheet 312. As shown in FIG. 9C, a mask 78 is placed on the substrate 77, and the second resin 72 is uniformly spread over the mask 78 with a squeegee 76. The first resin 71 is a thermosetting resin. Then, as shown in FIG. 9D, the mask 78 is removed from the substrate 77, and the resin sheet 312 is prepared. At this time, the resin sheet 312 is heated, and the state of the resin sheet 312 is "dried" or "cured".

FIG. 9E shows a step of placing the first end surface 303 side of the core body 300 on the resin sheet 312. As shown in FIG. 9E, a resin sheet 312 is placed on the etching plate 75, and the first end surface 303 side of the core body portion 300 is placed on the resin sheet 312. That is, the resin layer 311 applied to the first end surface 303 of the core body portion 300 is placed on the resin sheet 312. At this time, since the state of the resin layer 311 is "undried", the resin layer 311 applied to the side surfaces 301 and 302 of the core body part 300 hangs down to the first end surface 303 side of the core body part 300 due to gravity. flows. As a result, the thickness of the resin layer 311 becomes thicker toward the first end surface 303 of the core body portion 300, and an inclined surface 311a can be formed in the resin layer 311. Therefore, the thickness of the resin layer 311 covering the corners 305a, 305c of the core body 300 can be increased.

Preferably, the viscosity of the resin layer 311 (first resin 71) is smaller than the viscosity of the resin sheet 312 (second resin 72). This makes it easier to form the inclined surface 311a on the resin layer 311. The viscosity can be adjusted, for example, by adjusting the filler content, and the viscosity increases as the filler content increases. The filler content of the resin layer 311 is, for example, 10 vol% or more and 60 vol% or less, and the filler content of the resin sheet 312 is, for example, 60 vol% or more and 80 vol% or less.

Thereafter, the resin layer 311 and the resin sheet 312 are dried and cured in an oven. Furthermore, a resin layer 311 and a resin sheet 312 are formed on the second end surface 304 side of the core body section 300 as well as on the first end surface 303 side of the core body section 300 . That is, the resin layer 311 is applied to the side surfaces 301 and 302 and the second end surface 304 of the core body section 300, the resin sheet 312 is prepared, and the second end surface 304 side of the core body section 300 is placed on the resin sheet 312. In this way, the core 3 is manufactured.

According to this, by forming the resin layer 311 and the resin sheet 312 on the core body part 300, the core body part 300 can be covered with the insulating film 310 made up of the resin layer 311 and the resin sheet 312. Thereby, the corner portions of the core body portion 300 can be reliably covered with the insulating film 310. In other words, the thickness of the corner portions 310a to 310d of the insulating film 310 can be increased. Therefore, when manufacturing the inductor component 1 by winding the coils 41 and 42 around the core 3, even if the coils 41 and 42 contact the corner parts 310a to 310d of the insulating film 310, the corner parts 310a to 310d of the insulating film 310 can reduce chipping. Furthermore, since the resin sheet 312 is produced separately from the resin layer 311, thermal damage to the resin layer 311 during the process up to the completion of the product can be minimized. In other words, one possible method for increasing the thickness of the resin is usually to increase the thickness by applying multiple coats, but in that case, heating is required each time the resin is coated, so thermal damage accumulates in the resin layer. On the other hand, if the resin sheet 312 is created separately, it can be manufactured by heating once, so thermal damage can be minimized.

FIG. 10 is a plan view of the mask 78 used in FIG. 9C. As shown in FIG. 10, the mask 78 has a plurality of holes 78a. The hole 78a has a shape corresponding to the outer shape of the first end surface 303 and the second end surface 304 of the core body section 300. The resin sheet 312 can be manufactured by applying the second resin 72 to the holes 78a. In other words, with the mask 78, four resin sheets 312 can be produced at the same time. After drying or curing, the resin sheet 312 is hollowed out at a portion corresponding to the inner circumferential surface of the core body 300, and has a shape corresponding to the first end surface 303 and the second end surface 304 of the core body 300.

FIG. 11 is an enlarged image diagram of the core 3. In FIG. 11, a cross section perpendicular to the resin sheet 312 is cut with a wheel saw, the cut surface is polished with an automatic polisher with the surrounding area reinforced with resin, and the magnification is 200 times in the low vacuum observation mode of the SEM. I confirmed it. As shown in FIG. 11, the boundary between the resin layer 311 and the resin sheet 312 could be confirmed. This is because the filler content of the resin sheet 312 is greater than the filler content of the resin layer 311.

In FIG. 11, observation was performed using SEM, but observation may be performed using a fluorescence filter. Specifically, a cross section perpendicular to the resin sheet is cut with a wheel saw, the cut surface is reinforced with resin, the cut surface is polished with an automatic polisher to make it flat, and a light source is illuminated with an industrial microscope. The boundary between the resin sheet and the resin layer may be confirmed by observing the filter using a mercury lamp and a fluorescence filter with ND=4. Note that the boundary between the resin sheet and the resin layer may be confirmed by other methods.

(Core implementation example)
Next, an example of the core will be described.

The material of the resin sheet is, for example, thermosetting epoxy resin, polyimide resin, or the like. The material of the resin layer is, for example, thermosetting epoxy resin, polyimide resin, or the like. The viscosity of the material for the resin layer is lower than the viscosity of the material for the resin sheet. The material of the core body is, for example, a ferrite core, a metal core, or the like.

The thickness of the resin sheet is 50 μm to 200 μm, preferably 40 μm to 80 μm. The thickness of the resin layer on the first end surface side of the core body is 10 μm to 100 μm, preferably 10 μm to 20 μm. The thickness of the insulating film (resin sheet and resin layer) on the first end surface side of the core body is 60 μm to 300 μm, preferably 50 μm to 100 μm.

The width of the core body is 3.3 mm to 3.7 mm when the core body is a MnZn core, and 2.5 mm to 3.6 mm when the core body is a foil strip core. The width of the resin sheet is preferably equal to or slightly larger than the width of the core body, but may be smaller than the width of the core body.

The thickness of the central portion of the insulating film (the resin layer covering the central portion of the side surface of the core body) is 5 μm to 150 μm, preferably 20 μm to 100 μm. The thickness of the corner portions of the insulating film (resin layer and resin sheet covering the corner portions of the side surfaces of the core body) is thicker than the central portion of the insulating film, and is 10 μm to 300 μm.

(Second embodiment)
FIG. 12 is an enlarged sectional view of the core of the second embodiment. The second embodiment differs from the first embodiment in the configuration of the corner portions of the insulating film. Only this different configuration will be described below. The other configurations are the same as those in the first embodiment, and their explanation will be omitted.

As shown in FIG. 12, in the core 3A of the second embodiment, the corner portion 310a of the insulating film 310 includes a convex surface 312a provided on the resin sheet 312. The convex surface 312a is formed such that the thickness of the resin sheet 312 becomes continuously thicker toward both ends in the Z direction (lower side in FIG. 12). The thickness of the resin layer 311 may be thinner at the corner portion 305a of the core body portion 300. The thickness of the resin sheet 312 increases from the first end surface 303 of the core body portion 300 to the corner portion 305a. Thereby, the thickness of the corner portion 310a of the insulating film 310 becomes thicker than the thickness of the central portion 310e of the insulating film 310, and chipping of the corner portion 310a of the insulating film 310 can be prevented.

Next, a method for manufacturing the core 3A will be explained. Only the differences from the method for manufacturing the core 3 of the first embodiment will be explained.

In FIG. 9B, the state of the resin layer 311 is "hardened". Thereby, the inclined surface 311a is not formed in the resin layer 311, and the thickness of the resin layer 311 may be thinner at the corner portion 305a of the core body portion 300. In FIG. 9D, the state of the resin sheet 312 is set as "not dried" or "dried". In FIG. 9E, when placing the core body part 300 on the resin sheet 312, the core body part 300 is pressed against the resin sheet 312. By doing so, the resin sheet 312 is not in a "hardened" state, so the resin sheet 312 swells up at the corner 305a of the core body 300 and covers the corner 305a of the core body 300. Then, a convex surface 312a can be formed on the resin sheet 312.

(Third embodiment)
FIG. 13 is an enlarged sectional view of the core of the third embodiment. The third embodiment differs from the second embodiment in the configuration of the corner portions of the insulating film. Only this different configuration will be explained below. The other configurations are the same as those in the second embodiment, and their explanation will be omitted.

As shown in FIG. 13, in the core 3B of the third embodiment, on at least one of the first end surface 303 and the second end surface 304 of the core body 300, the insulating film 310 is made of resin that contacts the core body 300. It is composed of one layer of sheet 312. In this embodiment, the insulating film 310 on the first end surface 303 and the second end surface 304 of the core body section 300 is composed of one layer of a resin sheet 312 that contacts the core body section 300 . According to this, the insulating film 310 is composed of one layer on the first end surface 303 and the second end surface 304 of the core body portion 300, so that the dimension of the core 3 in the central axis direction can be reduced.

Next, a method for manufacturing the core 3B will be described. Only the differences from the method for manufacturing the core 3 of the second embodiment will be explained.

In FIG. 9B, the resin layer 311 attached to the first end surface 303 and corner portion 305a of the core body portion 300 is removed by the etching plate 75. As a result, in FIG. 9E, when the core body 300 is placed on the resin sheet 312 and the core body 300 is pressed against the resin sheet 312, the resin sheet 312 bulges at the corner 305a of the core body 300, causing the core body 300 to rise. Cover the corner 305a. Then, a convex surface 312a can be formed on the resin sheet 312.

(Fourth embodiment)
FIG. 14 is an explanatory diagram illustrating another method of manufacturing the core of the first embodiment. Only the parts that are different from the core manufacturing method of the first embodiment will be explained. In FIG. 9E, a base 81 is used instead of the heating device 80. The base 81 has a groove 81a.

As shown in FIG. 14, the resin layer 311 applied to the first end surface 303 of the core body portion 300 is placed on a resin sheet 312. As shown in FIG. At this time, since the state of the resin layer 311 is "undried", the resin layer 311 applied to the side surfaces 301 and 302 of the core body part 300 hangs down to the first end surface 303 side of the core body part 300 due to gravity. The water flows and is further discharged into the groove 81a of the base 81. By providing the groove 81a in this way, the excess resin layer 311 can be discharged. In this way, since the excess resin layer 311 can be discharged, the thickness of the insulating film 310 does not become too large, and it is possible to prevent the core 3 from increasing in size. Note that the base 81 may have a heating function.

(Spring index of bending pin member of coil)
The spring index of the bending pin member of the coil will be explained. FIG. 15 shows a state in which the bending pin member 410 is wound around the core 3. As shown in FIG. 15, the spring index Ks=curvature radius R1, R2 of the bending pin member/wire diameter r of the bending pin member. The radius of curvature R1 refers to the radius of curvature located at the corner of the outer circumferential surface of the core 3, and the radius of curvature R2 refers to the radius of curvature located at the corner of the inner circumferential surface of the core 3. The spring index Ks of the bending pin member 410 is smaller than 3.6 at both radii of curvature R1 and R2. On the other hand, it has been experimentally found that the spring index is 3.6 or more in the normal wire winding method.

Note that the present disclosure is not limited to the above-described embodiments, and design changes can be made without departing from the gist of the present disclosure. For example, the features of the first to fourth embodiments may be combined in various ways. The shape of the case and the shape of the core are not limited to this embodiment, and can be changed in design. Further, the number of coils is not limited to this embodiment, and the design can be changed. Although the coil is composed of a plurality of pin members, it may also be composed of a conducting wire.
In the first embodiment, if the resin layer 311 is "undried" or "dried" (that is, not "cured"), the resin layer 311 can be pressed against a flat surface even without the resin sheet 312. Accordingly, the inclined surface 311a may be formed on the resin layer 311.

1 Inductor parts 2 Case 21 Bottom plate part 22 Lid part 3, 3A, 3B Core 300 Core main body part 301 First side surface (outer peripheral surface)
301a First central portion 302 Second side surface (inner peripheral surface)
302a Second central part 303 First end surface (bottom surface)
304 Second end surface (top surface)
305a to 305d First to fourth corner parts 310 Insulating film 310a to 310d First to fourth corner parts 310e, 310f First and second central parts 311 Resin layer 311a Slanted surface 312 Resin sheet 312a Convex surface 41 First coil 410 Fold Bent pin members 411, 412 First and second straight pin members 42 Second coil 420 Bent pin members 421, 422 First and second straight pin members 51 to 54 First to fourth electrode terminals 60 Insulating resin body 70 Resin Tank 71 First resin 72 Second resin 78 Mask 80 Heating device 81 Base 81a Groove

Claims (6)

an annular core body;
an insulating film covering the core body,
The core main body has a first side surface on the outside in the radial direction, a second side surface on the inside in the radial direction, a first end surface and a second end surface facing each other in the central axis direction of the core main body, and the first side surface and the second side surface. a first corner provided between first end surfaces; a second corner provided between the first side surface and the second end surface; and a second corner provided between the second side surface and the first end surface. and a fourth corner provided between the second side surface and the second end surface,
The insulating film includes a first corner portion that covers the first corner portion, a second corner portion that covers the second corner portion, a third corner portion that covers the third corner portion, and a fourth corner portion. a fourth corner portion that covers, a first center portion that covers a first center portion located at the center in the center axis direction of the core body portion on the first side surface, and a first center portion that covers the first center portion located at the center in the center axis direction of the core body portion on the second side surface; a second central portion covering a second central portion located at the center of the second central portion;
At least one thickness of each of the first to fourth corner portions is thicker than at least one thickness of each of the first and second central portions,
The insulating film includes a resin layer that covers at least the first side surface and the second side surface of the core body portion, and a resin sheet that covers at least one of the first end surface and the second end surface of the core body portion. Equipped with
In the core, the insulating film is composed of two layers: the resin layer in contact with the core body and the resin sheet in contact with the resin layer . an annular core body;
an insulating film covering the core body,
The core main body has a first side surface on the outside in the radial direction, a second side surface on the inside in the radial direction, a first end surface and a second end surface facing each other in the central axis direction of the core main body, and the first side surface and the second side surface. a first corner provided between first end surfaces; a second corner provided between the first side surface and the second end surface; and a second corner provided between the second side surface and the first end surface. and a fourth corner provided between the second side surface and the second end surface,
The insulating film includes a first corner portion that covers the first corner portion, a second corner portion that covers the second corner portion, a third corner portion that covers the third corner portion, and a fourth corner portion. a fourth corner portion that covers, a first center portion that covers a first center portion located at the center in the center axis direction of the core body portion on the first side surface, and a first center portion that covers the first center portion located at the center in the center axis direction of the core body portion on the second side surface; a second central portion covering a second central portion located in the center of the second central portion;
At least one thickness of each of the first to fourth corner portions is thicker than at least one thickness of each of the first and second central portions,
The insulating film includes a resin layer that covers at least the first side surface and the second side surface of the core body, and a resin sheet that covers at least one of the first end surface and the second end surface of the core body. Equipped with
At least one of the first to fourth corner portions of the insulating film includes an inclined surface provided on the resin layer . an annular core body;
an insulating film covering the core body,
The core main body has a first side surface on the outside in the radial direction, a second side surface on the inside in the radial direction, a first end surface and a second end surface facing each other in the central axis direction of the core main body, and the first side surface and the second side surface. a first corner provided between first end surfaces; a second corner provided between the first side surface and the second end surface; and a second corner provided between the second side surface and the first end surface. and a fourth corner provided between the second side surface and the second end surface,
The insulating film includes a first corner portion that covers the first corner portion, a second corner portion that covers the second corner portion, a third corner portion that covers the third corner portion, and a fourth corner portion. a fourth corner portion that covers, a first center portion that covers a first center portion located at the center in the center axis direction of the core body portion on the first side surface, and a first center portion that covers the first center portion located at the center in the center axis direction of the core body portion on the second side surface; a second central portion covering a second central portion located at the center of the second central portion;
At least one thickness of each of the first to fourth corner portions is thicker than at least one thickness of each of the first and second central portions,
The insulating film includes a resin layer that covers at least the first side surface and the second side surface of the core body portion, and a resin sheet that covers at least one of the first end surface and the second end surface of the core body portion. Equipped with
At least one of the first to fourth corner portions of the insulating film includes a convex surface provided on the resin sheet . The core according to claim 2 or 3 , wherein the insulating film is comprised of one layer of the resin sheet that contacts the core body. A core according to any one of claims 1 to 4 ,
and a coil wound around the core. The inductor component according to claim 5 , wherein the coil is formed by connecting a plurality of pin members.

Images