Coil device

Abstract

The present invention provides a coil device that can prevent short circuit faults between turns of a coil portion. The coil device (2) comprises: a core portion (4) containing magnetic powder (41) and resin (42); and a coil portion (6) embedded in the core portion (4) and formed by winding an electric wire (6a) having an insulating coating (61). A resin-rich layer (40) is formed around the periphery of the coil portion (6).

Description

Technical Field

[0001] The present invention relates to a coil device. Background Art

[0002] For example, a coil device having a coil portion embedded within a body is known, as described in Patent Document 1. The coil device described in Patent Document 1 is obtained by embedding a coil portion having an insulating coating on its surface within a mold filled with magnetic powder and then compression-molding the coil.

[0003] However, in this type of coil assembly, if the resin in the mold is compressed together with the magnetic powder during molding, at least a portion of the magnetic powder may penetrate (penetrate) the insulating coating formed on the surface of the coil. Therefore, care must be taken to prevent short circuits between the turns of the coil from occurring through the magnetic powder.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2001-267160 Summary of the Invention

[0007] Technical problem to be solved by the invention

[0008] The present invention has been developed in view of such actual circumstances, and an object of the present invention is to provide a coil device capable of preventing short-circuit failures between turns of a coil portion.

[0009] Technical solutions to technical problems

[0010] In order to achieve the above object, the present invention provides a coil device having:

[0011] a body comprising magnetic powder and resin; and

[0012] The coil portion is embedded in the element body and is formed by winding an electric wire having an insulating coating.

[0013] A resin-rich layer is formed around the periphery of the coil portion.

[0014] The coil assembly of the present invention forms a resin-rich layer around the periphery of the coil portion. This resin-rich layer contains a relatively low amount of magnetic powder (or a relatively high amount of resin). Therefore, when the resin and magnetic powder are compressed together within the mold, the probability of magnetic powder penetrating the interior of the wire's insulation coating is reduced. Consequently, compared to conventional coil assemblies, the coil assembly of the present invention is less likely to have magnetic powder penetrate (penetrate) the wire's insulation coating, preventing short circuits between turns of the coil and improving the coil assembly's withstand voltage (ESD) performance.

[0015] A heat-sealing layer is preferably formed on the surface of the insulating coating. This structure allows the heat-sealing layer to function as a resin-rich layer. When the resin and magnetic powder are compressed together in the mold, the heat-sealing layer prevents the magnetic powder from entering the insulating coating of the wire. This also prevents short circuits between turns in the coil.

[0016] The magnetic powder preferably includes a first magnetic powder and a second magnetic powder having a smaller particle size than the first magnetic powder, and the resin-rich layer preferably includes the first and second magnetic powders. The first magnetic powder has a larger particle size than the second magnetic powder. Therefore, by including the first magnetic powder in the resin-rich layer, the inductance characteristics of the coil device as a whole are improved. Furthermore, since the second magnetic powder has a smaller particle size than the first magnetic powder, when the resin and magnetic powder are compressed together in the mold, the second magnetic powder is less likely to enter the insulating coating of the wire than the first magnetic powder. Therefore, by including the second magnetic powder in the resin-rich layer, the aforementioned phenomenon of magnetic powder entering the insulating coating of the wire can be effectively prevented.

[0017] Preferably, the second magnetic powder content in the resin-rich layer is greater than the first magnetic powder content near the coil portion. In this case, the second magnetic powder enters the grooves formed between the turns of the wire, or the second magnetic powder is arranged between multiple first magnetic powders, thereby increasing the magnetic powder content (density) within the element body. This results in a coil device with excellent inductance characteristics.

[0018] The magnetic powder contained in the resin-rich layer may also be composed of a soft magnetic metal. With this structure, a coil device having good high-frequency characteristics can be obtained.

[0019] The resin-rich layer may also contain magnetic powder having a particle size greater than the thickness of the insulating coating. For example, if a material with low conductivity, such as ferrite, is used as the magnetic powder, even if the magnetic powder enters the insulating coating of the wire, short circuits between turns in the coil are less likely to occur. Furthermore, by setting the magnetic powder particle size to the aforementioned size, a coil device with excellent inductance characteristics can be obtained.

[0020] The magnetic powder contained in the resin-rich layer may also be a metallic magnetic powder, and the resin-rich layer may contain the metallic magnetic powder having a particle size smaller than the thickness of the insulating coating. Using metallic magnetic powder as the magnetic powder can produce a coil device with excellent inductance characteristics. Furthermore, by setting the particle size of the metallic magnetic powder to the aforementioned size, the magnetic powder can be effectively prevented from entering the insulating coating of the wire.

[0021] The resin-rich layer may be composed only of (substantially) the resin. In this case, the periphery of the coil portion does not contain magnetic powder, thereby effectively preventing the magnetic powder from entering the insulating coating of the wire.

[0022] The electric wire can also be made of flat wire. This structure can increase the space factor of the coil portion within the element body, resulting in a coil device with good inductance characteristics. In addition, it can achieve low resistance of the coil portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a perspective view of the coil device according to the first embodiment of the present invention.

[0024] Figure 2 yes Figure 1 An exploded perspective view of the coil arrangement shown.

[0025] Figure 3A yes Figure 1 The coil arrangement is shown in a cross-sectional view along line IIIA-IIIA.

[0026] Figure 3B yes Figure 1 A cross-sectional view of the coil arrangement along line IIIB-IIIB is shown.

[0027] Figure 4 is Figure 3A A local enlarged view of the area surrounded by the dotted line.

[0028] Figure 5 It is a cross-sectional view showing the electric wire structure of a coil device according to a third embodiment of the present invention.

[0029] Figure 6 It is a cross-sectional view of a coil device according to a fourth embodiment of the present invention.

[0030] Explanation of symbols

[0031] 2.102...coil device

[0032] 4, 104... core

[0033] 4a...External surface of the installation side

[0034] 4a1, 4b1...installation slots

[0035] 4b...External surface of the reverse mounting side

[0036] 4c……side (lateral outer surface)

[0037] 4c1... Main mounting side

[0038] 4c2...Auxiliary mounting side

[0039] 4c3a, 4c3b, 4c4a, 4c4b...non-installation side

[0040] 40, 140...resin-rich layer

[0041] 41...Magnetic powder

[0042] 41a……first magnetic powder

[0043] 41b...Second magnetic powder

[0044] 42...resin

[0045] 6.106...coil part

[0046] 6a, 106a...wires

[0047] 60...wire

[0048] 61...Insulation coating

[0049] 610...first insulating coating

[0050] 620... Second insulating coating (thermal welding layer)

[0051] 6b...lead part

[0052] 6c...Joint

[0053] 8...Terminal electrode

[0054] 80...Main terminal body

[0055] 82……Sub-terminal body

[0056] 83, 84... elastic sheet

[0057] 85...lead support DETAILED DESCRIPTION

[0058] Hereinafter, the present invention will be described based on the embodiments shown in the drawings.

[0059] First embodiment

[0060] like Figure 1 As shown, the coil device 2 of the first embodiment of the present invention comprises: a core portion (element body) 4 as a compression-molded body containing magnetic powder and resin, a coil portion 6 (see FIG. 1 ) embedded in the core portion 4 and formed by winding an electric wire 6a with an insulating coating (insulating film). Figure 3A ), terminal electrode 8 connected to lead portion 6b of wire 6a by joint portion 6c. Coil device 2 is used as a power transformer, power inductor, noise elimination inductor, etc., in electronic equipment, electrical equipment, vehicle-mounted equipment, etc.

[0061] In this embodiment, the winding axis of the coil 6 is defined as the Z axis, and axes perpendicular to the Z axis are defined as the X and Y axes. In this embodiment, the X axis coincides with the direction in which the pair of terminal electrodes 8 face each other, but this is not particularly limited.

[0062] The dimensions of the coil device 2 are not particularly limited. For example, the width in the X-axis direction is 1.0 to 20 mm, the width in the Y-axis direction is 1.0 to 20 mm, and the height is 1.0 to 10 mm.

[0063] like Figure 2 As shown, the core 4 has a mounting side outer surface 4a formed at the lower portion in the Z-axis direction and an anti-mounting side outer surface 4b formed at the upper portion in the Z-axis direction. A side surface 4c serving as a lateral outer surface is formed between the mounting side outer surface 4a and the anti-mounting side outer surface 4b.

[0064] In the present embodiment, the side surface 4c is formed by a combination of multiple planes and curved surfaces, but is not particularly limited thereto. As a whole, it can be a curved surface, or as a whole, it can be a polygonal side surface. In the present embodiment, when observing the core 4 from the top or bottom of the Z-axis direction, it is preferably an asymmetric shape. This is because, when observing the core 4 from the top or bottom of the Z-axis direction, it is easy to identify the shape or direction of the coil device.

[0065] The side surface 4c of the core portion 4 includes a pair of main mounting side surfaces 4c1 located on opposite sides of each other in the X-axis direction. In this embodiment, the main mounting side surfaces 4c1 are formed flat to conform to the shape of the main terminal body 80 of the terminal electrode 8. However, if the inner surface of the main terminal body 80 is curved, a curved surface can also be formed to conform thereto. Furthermore, when viewed from above in the Z-axis direction, the side surface 4c of the core portion 4 includes a secondary mounting side surface 4c2 located clockwise from the main mounting side surface 4c1. The lead portion 6b protrudes from the secondary mounting side surface 4c2.

[0066] Furthermore, when viewed from above in the Z-axis direction, the side surface 4c of the core 4 includes non-mounting side surfaces 4c3a, 4c4a or 4c3b, 4c4b, clockwise from the secondary mounting side surface 4c2. In this embodiment, the side surfaces 4c1, 4c1 located on opposite sides have the same shape and area, and the same applies to the side surfaces 4c2, 4c2.

[0067] The non-mounting side surfaces 4c3a and 4c3b located on opposite sides have different widths in the X-axis direction. Furthermore, one of the non-mounting side surfaces 4c4a and 4c4b located on opposite sides is flat, while the other is curved, and thus have different shapes. That is, in this embodiment, the non-mounting side surfaces 4c3a and 4c3b (4c4a and 4c4b) located on opposite sides have different shapes or sizes. This configuration allows the core 4 to have an asymmetric shape when viewed from above or below in the Z-axis direction.

[0068] Each terminal electrode 8 has a main terminal body 80. The main terminal body 80 has a rectangular flat plate shape according to the shape of the main mounting side surface 4c1 of the core 4, but can have a corresponding shape by changing the shape of the main mounting side surface 4c1 as described above.

[0069] like Figure 3B As shown, the lower elastic piece 83 is bent from the main terminal body 80 and integrally formed at the lower part of the main terminal body 80 in the Z-axis direction. In addition, the upper elastic piece 84 is bent from the main terminal body 80 and integrally formed at the upper part of the main terminal body 80 in the Z-axis direction. Figure 2 As shown, the lower elastic piece 83 is fitted into the lower mounting groove 4 a 1 formed in the mounting-side outer surface 4 a , which is the bottom surface of the core 4 .

[0070] The bottom of the lower mounting groove 4a1 is inclined toward the central axis of the coil portion 6 and toward the upper direction of the Z-axis direction, and the lower elastic piece 83 is difficult to disengage after being engaged with the lower mounting groove 4a1. The upper elastic piece 84 is engaged with the upper mounting groove 4b1 formed on the anti-mounting side outer surface 4b of the upper surface of the core portion 4. The bottom of the upper mounting groove 4b1 is inclined toward the central axis of the coil portion 6 and toward the lower direction of the Z-axis direction, and the upper elastic piece 84 is difficult to disengage after being engaged with the upper mounting groove 4b1.

[0071] like Figure 2 As shown, a sub-terminal body 82 is integrally formed with the main terminal body 80. The sub-terminal body 82 is bent so as to intersect the surface of the main terminal body 80 at a predetermined angle. This angle substantially coincides with the intersection angle between the main mounting surface 4c1 and the sub-mounting surface 4c2 of the core 4.

[0072] The auxiliary terminal body 82 has an inner surface shape corresponding to the outer surface shape of the auxiliary mounting surface 4c2. In this embodiment, it is a flat plate shape, but it can also be set to a curved surface shape according to the outer surface shape of the auxiliary mounting surface 4c2. Figure 3A As shown, the sub-terminal body 82 faces the outer surface of the sub-mounting surface 4c2, but they do not necessarily need to be in contact with each other.

[0073] like Figure 2 As shown, the lead support portion 85 is bent outward from the auxiliary terminal body 82 and integrally formed at the upper portion of the auxiliary terminal body 82 in the Z-axis direction.

[0074] like Figure 3A and Figure 3B As shown, the coil portion 6 is a portion in which the electric wire 6a is wound into a coil shape, and at least a pair of lead portions 6b serving as both ends of the electric wire 6a are led out of the coil portion 6 to the outside of the core portion 4. In the illustrated embodiment, the pair of lead portions 6b are led out of the coil portion 6 from the secondary mounting side surface 4c2 of the core portion 4 in a direction substantially perpendicular to the side surface.

[0075] The electric wire 6a is composed of, for example, a conductive wire 60 and an insulating coating 61 covering the outer periphery of the conductive wire 60. The conductive wire 60 is made of, for example, Cu, Al, Fe, Ag, Au, phosphor bronze, or the like. The insulating coating 61 is made of, for example, polyurethane, polyamide-imide, polyimide, polyester, polyester-imide, polyester-nylon, or the like. In this embodiment, the cross-section of the electric wire 6a is circular. Furthermore, as described later, the insulating coating 61 is composed of two layers: a first insulating coating 610 and a second insulating coating 620.

[0076] The thickness of the insulating coating layer 61 is preferably 100 to 300 μm, more preferably 200 to 300 μm.

[0077] The core 4 is composed of a composite material comprising magnetic powder (magnetic powder) and resin, and is formed by compression molding or injection molding particles comprising the magnetic powder and resin (binder resin). While the magnetic powder is not particularly limited, metal magnetic powders (soft magnetic metal magnetic powders) such as sendust powder (Fe-Si-Al; iron-silicon-aluminum), Fe-Si-Cr (iron-silicon-chromium), permalloy (Fe-Ni), carbonyl iron powders, carbonyl nickel powders, amorphous powders, and nanocrystalline powders are preferably used.

[0078] The particle size of the magnetic powder is preferably 0.5 to 50 μm. In this embodiment, the magnetic powder is a metal magnetic powder, and the outer periphery of the particles is preferably an insulating film. Examples of the insulating film include metal oxide films, resin films, and chemical films such as phosphorus or zinc films.

[0079] However, the magnetic powder may also be ferrite magnetic powder such as Mn-Zn or Ni-Cu-Zn. The binder resin is not particularly limited, and examples thereof include epoxy resin, phenol resin, acrylic resin, polyester resin, polyimide, polyamide-imide, silicone resin, and combinations thereof.

[0080] In this embodiment, the core 4 located around the coil 6 is insulated, and a resin-rich layer 40 is formed around the coil 6. The resin-rich layer 40 constitutes a portion of the core 4 and contains both magnetic powder and resin.

[0081] The following, such as Figure 4 As shown, the magnetic powder contained in the core 4 is described as "magnetic powder 41," and the resin contained in the core 4 is described as "resin 42." In this embodiment, the resin-rich layer 40 contains magnetic powder 41 and resin 42. The types of magnetic powder 41 and resin 42 contained in the resin-rich layer 40 are the same as those contained in the portion other than the resin-rich layer 40, but they may be different. For example, the magnetic powder 40 contained in the resin-rich layer 40 may be ferrite, for example, and the magnetic powder 40 contained in the portion other than the resin-rich layer 40 may be metallic magnetic powder, for example.

[0082] In this embodiment, a difference (gradient) is provided in the content of magnetic powder 41 and resin 42 in core 4, so that the resin component is increased in resin-rich layer 40, making it resin-rich. Furthermore, the content of magnetic powder 41 and resin 42 in resin-rich layer 40 can be determined through simple quantitative analysis using cross-sectional EDS. In this case, the weight ratio (or atomic ratio) of the metal element (e.g., Fe) constituting magnetic powder 41 in resin-rich layer 40 is reduced, while the weight ratio (or atomic ratio) of the element (e.g., C) constituting resin 42 is increased in resin-rich layer 40, compared to other portions (e.g., the center portion of core 4).

[0083] The magnetic powder 41 contained in the resin-rich layer 40 is preferably made of a soft magnetic metal. In this case, a coil device 2 having excellent high-frequency characteristics can be obtained.

[0084] In this embodiment, the resin-rich layer 40 is composed of both magnetic powder 41 and resin 42. However, the composition of the resin-rich layer 40 is not limited to this and may be composed solely of resin 42. Alternatively, the content of resin 42 may be significantly greater than the content of magnetic powder 41 (in fact, the resin-rich layer 40 may be composed solely of resin). Furthermore, the insulating coating 61 composed solely of resin is formed on the wire 6a that constitutes the coil portion 6. However, the resin-rich layer 40 and the insulating coating 61 are formed separately.

[0085] In the resin-rich layer 40, for example, the central portion ( Figure 3A The content of the resin 42 is higher than that of the peripheral portion of the winding axis C of the coil portion 6 shown in FIG. Alternatively, in the resin-rich layer 40, for example, the content of the resin 42 is higher than that of the central portion of the core 4 ( Figure 3A The content of magnetic powder 41 is reduced compared to the peripheral portion of the winding axis C of the coil portion 6 shown in FIG. 2 . In addition, the content of resin 42 (or magnetic powder 41) in the resin-rich layer 40 may be increased (or decreased) compared to the portion other than the central portion of the core 4.

[0086] like Figure 3A and Figure 3B As shown, the resin-rich layer 40 is formed to have a predetermined thickness and surround the periphery (outer peripheral surface) of the coil portion 6. More specifically, the resin-rich layer 40 is formed on the insulating coating layer 61 of the electric wire 6a (see FIG. 1 ) with a predetermined thickness in a manner that follows the outer peripheral surface shape of the coil portion 6. Figure 4 ) on the outer surface of the insulating coating layer 61. The resin-rich layer 40 has a function of preventing the magnetic powder 41 (especially the first magnetic powder 41a described later) from entering (penetrating) the insulating coating layer 61.

[0087] The shape of the resin-rich layer 40 is not limited to the example shown in the figure. For example, the resin-rich layer 40 may be formed in a location away from the coil portion 6 in addition to the periphery of the coil portion 6. For example, a portion of the resin-rich layer 40 may be formed around the lead portion 6b of the wire 6a. Alternatively, the resin-rich layer 40 may be formed partially around the periphery of the coil portion 6. For example, the resin-rich layer 40 may be selectively formed at a location where the pressure is high when the resin and magnetic powder are compressed together in the mold during molding.

[0088] The thickness of resin-rich layer 40 is preferably 5 to 200 μm, more preferably 50 to 150 μm, and particularly preferably 80 to 120 μm. Furthermore, resin-rich layer 40 is thicker than insulating coating 61 formed on the surface of conductive wire 60. The thickness of resin-rich layer 40 can be determined based on, for example, a cross-sectional SEM image.

[0089] like Figure 4 As shown, magnetic powder 41 includes first magnetic powder (large particles or coarse powder) 41a and second magnetic powder (small particles or fine powder) 41b having a smaller particle size than first magnetic powder 41a. First magnetic powder 41a is included in core 4 primarily to increase the inductance of core 4, while second magnetic powder 41b is included in core 4 primarily to increase the packing density of magnetic powder 41 within core 4. First magnetic powder 41a and second magnetic powder 41b may have the same or different compositions.

[0090] The resin-rich layer 40 contains first magnetic powder 41a and second magnetic powder 41b. The resin-rich layer 40 contains first magnetic powder 41a having a particle size of, for example, 20 to 50 μm, and may contain second magnetic powder 41b having a particle size of 5 to 10 μm.

[0091] Furthermore, first magnetic powder 41a and second magnetic powder 41b are also contained in a region outside of resin-rich layer 40 in core 4 (e.g., the center of core 4). The particle sizes of first magnetic powder 41a and second magnetic powder 41b contained in this region may be the same as or different from the particle sizes of first magnetic powder 41a and second magnetic powder 41b contained in resin-rich layer 40.

[0092] The second magnetic powder 41b is arranged so as to be located between each of the plurality of first magnetic powders 41a (or so as to fill each of the plurality of first magnetic powders 41a). In the resin-rich layer 40, the content of the second magnetic powder 41b becomes greater than that of the first magnetic powder 41a at a position close to the coil portion 6. That is, in the resin-rich layer 40, the content of the second magnetic powder 41b increases as it approaches the coil portion 6, and the content of the first magnetic powder 41a increases as it moves away from the coil portion 6. However, the distribution of the content of the magnetic powder 41 and the resin 42 in the resin-rich layer 40 is not limited to this, and may be constant throughout the entire area of ​​the resin-rich layer 40.

[0093] The second magnetic powder 41b enters (fills) the substantially V-shaped grooves formed between adjacent turns of the electric wire 6a. On the other hand, the first magnetic powder 41a does not enter the grooves and is preferably arranged relatively far from the coil portion 6.

[0094] Resin-rich layer 40 contains magnetic powder 41 (first magnetic powder 41a) having a particle size larger than the thickness of insulating coating 61 formed on the surface of conductive wire 60. Thus, when resin-rich layer 40 contains first magnetic powder 41a having a particle size larger than the thickness of insulating coating 61, the material constituting magnetic powder 41 is preferably a material with low conductivity (for example, Ni-Zn ferrite). In this case, the material constituting second magnetic powder 41b can also be a material with low conductivity, similar to first magnetic powder 41a. Alternatively, when the particle size of second magnetic powder 41b is smaller than the thickness of insulating coating 61, the material constituting second magnetic powder 41b can also be a material with high conductivity.

[0095] Then, Figure 1 The manufacturing method of the coil device 2 shown in FIG. Figure 3A and Figure 3B As shown, a coil portion 6 in which an electric wire 6a is wound in a coil shape is prepared. The coil portion 6 is formed of, for example, an air-core coil. As the electric wire 6a, an electric wire having an insulating coating 61 formed on the surface of a conductive wire 60 is used.

[0096] Next, the coil portion 6 is immersed in a resin liquid so that the resin adheres to the surface of the coil portion 6. As the resin liquid, the resin 42 constituting the resin-rich layer 40 is used (see Figure 4 At this time, by appropriately adjusting the time for immersing the coil portion 6 in the resin liquid, etc., a resin layer having a thickness of 5 to 200 μm can be formed on the surface of the coil portion 6 .

[0097] Next, in a state where the resin layer formed on the surface of the coil portion 6 is solidified, the core portion 4 (element body) is used to cover the entire interior of the coil portion 6, so that the lead portion 6b of the wire 6a constituting the coil portion 6 is exposed from the outer surface of the core portion 4. The core portion 4 is formed by, for example, filling a mixture containing magnetic powder and binder resin into the cavity of the mold while the coil portion 6 is embedded in the cavity of the mold, and compressing the entirety (heating and pressurizing). As the magnetic powder, the magnetic powder 41 constituting the resin-rich layer 40 is used (see Figure 4 ). In addition, a magnetic powder including a first magnetic powder 41a and a second magnetic powder 41b is used as the magnetic powder 41. As a method for compression molding, a mold can be used, and oil pressure or water pressure can also be used.

[0098] When the resin in the mold is compressed together with the magnetic powder, a portion of the magnetic powder in the mold enters the interior of the resin layer formed on the surface of coil portion 6, thereby forming a resin layer containing this magnetic powder on the surface of coil portion 6. As described above, the magnetic powder is composed of magnetic powder 41 constituting resin-rich layer 40, and the resin layer is composed of resin 42 constituting resin-rich layer 40. Therefore, the magnetic powder in the mold enters the interior of the resin layer formed on the surface of coil portion 6, thereby forming resin-rich layer 40 containing magnetic powder 41 and resin 42.

[0099] By adjusting the pressure during compression molding, the amount of magnetic powder that enters the resin layer formed on the surface of the coil portion 6 can be adjusted, allowing the content of magnetic powder 41 in the resin-rich layer 40 to be set to a desired value. After molding, the lead portion 6b is removed along with the molded body. The outer surface of the core portion 4 can also be coated with glass or insulating resin.

[0100] While forming the core 4 or before or after, prepare Figure 2 The terminal electrode 8 is shown. The terminal electrode 8 is preferably made of a metal (including alloys) such as Cu and phosphor bronze. The terminal electrode 8 can be obtained by cutting and bending a single metal plate or a composite metal plate such as a cladding material of uniform thickness by stamping or the like. A plating film or the like that improves adhesion with soldering may also be formed on the surface of the terminal electrode 8. A lower elastic sheet 83 and an upper elastic sheet 84 may be formed on the terminal electrode 8 as needed.

[0101] Then, a joint portion 6c is formed at the tip of the lead support portion 85 to connect with the lead portion 6b. In the joint portion 6c, the lead portion 6b and the tip of the lead support portion 85 are joined together by, for example, laser welding. The method for forming the joint portion 6c is not limited to laser welding, and arc welding, ultrasonic welding, thermocompression welding, and soldering can be used as examples.

[0102] It is preferable to remove the resin film of the lead portion 6b before forming the bonding portion 6c. It is further preferable that the resin film of the lead portion 6b be removed before the terminal electrode 8 is mounted on the outer surface of the core portion 4. As described above, it is possible to obtain Figure 1 The coil arrangement 2 is shown.

[0103] In the coil device 2 of this embodiment, a resin-rich layer 40 is formed around the periphery of the coil portion 6. The resin-rich layer 40 contains a relatively low content of magnetic powder 41 (or a relatively high content of resin 42). Therefore, when the resin and magnetic powder 41 are compressed together within the mold, the probability of magnetic powder 41 penetrating into the insulating coating 61 of the wire 6a is reduced. Consequently, in the coil device 2 of this embodiment, compared to conventional coil devices, the magnetic powder 41 is less likely to penetrate (or pierce) the insulating coating 61 of the wire 6a, preventing short circuit failures between turns of the coil portion 6 and improving the withstand voltage (ESD) of the coil device 2.

[0104] In this embodiment, magnetic powder 41 includes first magnetic powder 41a and second magnetic powder 41b having a smaller particle size than first magnetic powder 41a. The resin-rich layer 40 contains both first magnetic powder 41a and second magnetic powder 41b. Since the particle size of first magnetic powder 41a is larger than that of second magnetic powder 41b, the inclusion of first magnetic powder 41a in resin-rich layer 40 improves the inductance characteristics of the coil device 2 as a whole. Furthermore, since the particle size of second magnetic powder 41b is smaller than that of first magnetic powder 41a, when the resin and magnetic powder 41 are compressed together in the mold, second magnetic powder 41b is less likely to enter the insulating coating 61 of the wire 6a than first magnetic powder 41a. Therefore, the inclusion of second magnetic powder 41b in resin-rich layer 40 effectively prevents the aforementioned intrusion of magnetic powder 41 into the insulating coating 61 of the wire 6a.

[0105] Furthermore, in this embodiment, in the resin-rich layer 40, the content of the second magnetic powder 41b is greater than that of the first magnetic powder 41a near the coil portion 6. In this case, the second magnetic powder 41b enters the inner side of the grooves formed between the turns of the wire 6a. Furthermore, the second magnetic powder 41b is arranged between the multiple first magnetic powders 41a. Therefore, the content ratio (density) of the magnetic powder 41 within the core portion 4 (element body) can be increased. Consequently, a coil device 2 with excellent inductance characteristics can be obtained.

[0106] Furthermore, in this embodiment, the resin-rich layer 40 contains magnetic powder 41 (first magnetic powder 41a) having a particle size larger than the thickness of the insulating coating 61. For example, if a material with low conductivity, such as ferrite, is used as the first magnetic powder 41a, even if the first magnetic powder 41a enters the insulating coating 61 of the wire 6a, a short circuit failure between the turns of the coil portion 6 is unlikely to occur. Furthermore, by setting the particle size of the first magnetic powder 41a to the above-described size, a coil device 2 having excellent inductance characteristics can be obtained.

[0107] Second embodiment

[0108] The coil device according to the second embodiment of the present invention differs only in its manufacturing method, and its structure is the same as that of the first embodiment described above. Detailed description of the parts common to the first embodiment will be omitted below.

[0109] In the manufacturing method of the coil device of the present embodiment, only the method of forming the resin-rich layer 40 is different. That is, in the present embodiment, first, a coil portion 6 in which the electric wire 6a is wound into a coil shape is prepared, and the core portion 4 (element body) is used to cover the entire interior including the coil portion 6, so that the lead portion 6b of the electric wire 6a is exposed from the outer surface of the core portion 4. Then, in this state, the core portion 4 is preliminarily formed. The preliminarily forming of the core portion 4 is performed as follows, for example, in a state where the coil portion 6 is embedded in the cavity of the mold, a mixture containing magnetic powder and binder resin is filled in the cavity inside the mold, and the entirety is compressed (heated and pressurized). In the preliminarily forming, the core portion 4 is compressed at a pressure smaller than that in the formal forming described later. As the magnetic powder, Figure 4 The magnetic powder 41 shown includes a first magnetic powder 41a and a second magnetic powder 41b.

[0110] Next, the core 4 (preliminary formed body) obtained by preliminary forming is immersed in a resin liquid. As the resin liquid, the resin 42 constituting the resin-rich layer 40 is used. At this time, the resin liquid flows into the interior of the core 4 through the extremely small gap formed around the lead portion 6b of the electric wire 6a by the capillary phenomenon, and reaches the peripheral portion of the coil portion 6. As a result, the resin liquid adheres to the surface of the coil portion 6 in a manner covering the periphery of the coil portion (in a surrounding manner), and forms a resin layer on the surface of the coil portion 6. By appropriately adjusting the time for immersing the core 4 in the resin liquid, etc., a resin layer with a thickness of 5 to 200 μm can be formed on the surface of the coil portion 6.

[0111] Next, the core 4 is formally formed. In the formal forming, the core 4 is compressed (heated and pressurized) with a pressure greater than that in the preliminary forming. When the core 4 is compressed, a portion of the magnetic powder in the mold enters the interior of the resin layer formed on the surface of the coil portion 6, and a resin layer containing the magnetic powder is formed on the surface of the coil portion 6. As described above, the magnetic powder is composed of the magnetic powder 41 constituting the resin-rich layer 40, and the resin layer is composed of the resin 42 constituting the resin-rich layer 40. Therefore, by the magnetic powder in the mold entering the interior of the resin layer formed on the surface of the coil portion 6, a resin-rich layer 40 containing the magnetic powder 41 and the resin 42 can be obtained (refer to Figure 3A and Figure 3B ).

[0112] In this embodiment, the resin liquid is filled not only around the coil portion 6 but also around the lead portion 6b of the wire 6a, forming a resin layer around this perimeter. Therefore, during compression of the core 4 (during the final molding process), the magnetic powder within the mold also enters the resin layer formed around the lead portion 6b, forming a resin-rich layer 40. Alternatively, the resin-rich layer 40 may be formed in areas other than the perimeter of the lead portion 6b.

[0113] In this embodiment as well, the same coil device 2 as in the first embodiment is obtained, and the same effects as in the first embodiment are obtained.

[0114] Third embodiment

[0115] The coil device according to the third embodiment of the present invention differs only in its manufacturing method, and its structure is the same as that of the first embodiment described above. Detailed description of the parts common to the first embodiment will be omitted below.

[0116] In this embodiment, only the method of forming the resin-rich layer 40 is different. That is, in this embodiment, first, as shown in FIG. Figure 3A and Figure 3B As shown in FIG. 1 , a coil portion 6a is prepared in which an electric wire 6a is wound into a coil shape. The coil portion 6a is composed of, for example, an air-core coil. Figure 5 As shown, the insulating coating 61 formed on the surface of the conductive wire 60 includes a first insulating coating 610 and a second insulating coating 620 . The first insulating coating 610 is formed on the surface of the conductive wire 60 , and the second insulating coating 620 is formed on the surface of the first insulating coating 610 .

[0117] The resin constituting the second insulating coating layer 620 can be a resin that melts more easily than the resin constituting the first insulating coating layer 610. In this embodiment, the resin constituting the second insulating coating layer 620 is the resin 42 constituting the resin-rich layer 40. For example, the first insulating coating layer 610 is made of polyamide-imide, and the second insulating coating layer 620 is made of a material to which an additive has been added.

[0118] In this embodiment, during the formation stage of the coil portion 6, for example, the air-core coil is heated, thereby melting the second insulating coating 620 to form a heat-welding layer (self-welding layer). As a result, the surface of the first insulating coating 610 is entirely covered by the heat-welding layer, and the adjacent turns of the coil portion 6 are connected (bonded) to each other through the heat-welding layer. As a result, the adjacent turns of the coil portion 6a are integrated with each other via the heat-welding layer. In addition, as described later, when the resin in the mold is compressed together with the magnetic powder (heating and pressurizing) in a heated atmosphere, the second insulating coating 620 can also be melted to form a heat-welding layer on the surface of the first insulating coating 610.

[0119] Next, the core 4 (element) is used to cover the entire interior including the coil 6, so that the lead 6b of the wire 6a constituting the coil 6 is exposed from the outer surface of the core 4. The core 4 is formed by, for example, filling the cavity of the mold with a mixture containing magnetic powder and binder resin while the coil 6 is embedded in the cavity of the mold, and compressing the entire cavity. As the magnetic powder, Figure 4 The magnetic powder 41 shown includes a first magnetic powder 41a and a second magnetic powder 41b.

[0120] When the resin in the mold is compressed together with the magnetic powder in a heated atmosphere (heating and pressurizing), a portion of the heat-welding layer formed on the surface of the first insulating coating 610 melts and seeps out into the interior of the core portion 4 located at the peripheral portion of the coil portion 6. As a result, the peripheral portion of the coil portion 6 becomes resin-rich due to the amount of the melted heat-welding layer. As described above, the magnetic powder is composed of the magnetic powder 41 constituting the resin-rich layer 40, and the heat-welding layer is composed of the resin 42 constituting the resin-rich layer 40. Therefore, by causing the heat-welding layer formed on the surface of the first insulating coating 610 to seep out of the peripheral portion of the coil portion 6, a resin-rich layer 40 containing the magnetic powder 41 and the resin 42 is obtained (see Figure 3A and Figure 3B ).

[0121] Furthermore, by adjusting the heating temperature during compression molding, the amount of the heat-welding layer that seeps into the core 4 can be adjusted, allowing a heat-welding layer with a thickness of 5 to 200 μm to be formed on the surface of the coil 6. Furthermore, the content of the resin 42 in the resin-rich layer 40 can be set to a desired value.

[0122] This embodiment also provides the same coil device and effects as the first embodiment. In particular, this embodiment forms a heat-welding layer (a heat-welding layer formed based on the second insulating coating layer 620) on the surface of the insulating coating 61. This allows the heat-welding layer to function as a resin-rich layer 40. When the resin 42 and magnetic powder 41 are compressed together within the mold, the heat-welding layer prevents the magnetic powder 41 from entering the insulating coating 61 of the wire 6. Therefore, this embodiment also prevents short-circuit failures between turns of the coil portion 6.

[0123] Fourth embodiment

[0124] At once Figure 6 The coil device 102 of the fourth embodiment of the present invention shown here differs only in the following points, and the rest of the structure is the same as that of the first embodiment. In the drawings, the same reference numerals are used for the same components as those of the first embodiment, and detailed description thereof will be omitted.

[0125] like Figure 6 As shown, the coil device 110 includes a coil portion 106 and a resin-rich layer 140. The coil portion 106 includes an electric wire 106a, and the electric wire 106a is different from the electric wire 6a of the first embodiment in that it is composed of a flat wire.

[0126] The electric wire 106a is wound according to a common standard width. However, the winding method of the electric wire 106a is not limited to this, and the electric wire 106a may be wound by edge width winding or α winding, for example.

[0127] In the example shown, the coil portion 106 is formed in two layers in the Z-axis direction (winding axis direction), but may be formed in more than two layers. In addition, the coil portion 106 is formed in four layers in the X-axis direction or the Y-axis direction, but may be formed in more than four layers.

[0128] The resin-rich layer 140 is formed on the periphery of the coil portion 106 and covers (surrounds) the periphery of the coil portion 106 formed by winding a rectangular electric wire.

[0129] This embodiment also achieves the same effects as the first embodiment. In particular, in this embodiment, the electric wire 106a is formed of a flat wire. This increases the space factor of the coil portion 106 within the core 4 (element body), resulting in a coil device 102 with excellent inductance characteristics. Furthermore, the resistance of the coil portion 6 can be reduced.

[0130] In addition, the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention.

[0131] In each of the above embodiments, the resin-rich layer 40 may include magnetic powder 41 (first magnetic powder 41a) having a particle size smaller than the thickness of the insulating coating 61 formed on the surface of the conductive wire 60. In this manner, when the resin-rich layer 40 includes first magnetic powder 41a having a particle size smaller than the thickness of the insulating coating 61, a highly conductive material (metal magnetic powder) may be used as the material constituting the first magnetic powder 41a. Using metal magnetic powder as the first magnetic powder 41a allows for a coil device 2 having excellent inductance characteristics. Furthermore, by setting the particle size of the first magnetic powder 41a (metal magnetic powder) to the aforementioned size, the first magnetic powder 41a can be effectively prevented from entering the insulating coating 61 of the conductive wire 6a.

[0132] In each of the above embodiments, the resin-rich layer 40 may be (substantially) composed only of the resin 42. In this case, the magnetic powder 42 is not contained in the periphery of the coil portion 6, and thus the magnetic powder 41 can be effectively prevented from entering the insulating coating 61 of the electric wire 6a.

[0133] In each of the above embodiments, the resin-rich layer 40 may be composed only of the second magnetic powder (small particles) 41 b . In this case, the particle size of the second magnetic powder 41 b is preferably equal to or smaller than the thickness of the insulating coating layer 61 .

[0134] In each of the above embodiments, Figure 2 The side surfaces 4c1, 4c1 shown on opposite sides have the same shape and area, but they may be different. The same applies to the side surfaces 4c2, 4c2.

[0135] In each of the above embodiments, the coil portion 6 is a circular coil shape, but is not particularly limited thereto and may also be a square coil shape, a polygonal coil shape, an elliptical coil shape, or other coil shapes. In addition, the shape of the core portion 4 is not particularly limited thereto and may also be a cylindrical shape, an elliptical column, a polygonal column, etc.

[0136] In each of the above-described embodiments, the type of magnetic powder 41 contained in the resin-rich layer 40 may be appropriately changed as needed.

Claims

1. A coil device comprising: a body comprising magnetic powder and resin; and The coil portion is embedded in the element body and is formed by winding an electric wire having an insulating coating. A resin-rich layer is formed on the periphery of the coil portion and is separate from the insulating coating layer. The thickness of the resin-rich layer is 50 μm to 150 μm. The magnetic powder includes a first magnetic powder and a second magnetic powder having a smaller particle size than the first magnetic powder. The resin-rich layer contains the first magnetic powder and the second magnetic powder, The particle size of the first magnetic powder is 20 μm to 50 μm, The particle size of the second magnetic powder is 5 μm to 10 μm, In the resin-rich layer, the content of the second magnetic powder is greater than that of the first magnetic powder at a position close to the coil portion. In the resin-rich layer, the content of the second magnetic powder increases as it approaches the coil portion, and the content of the first magnetic powder increases as it moves away from the coil portion.

2. The coil device according to claim 1, wherein A heat-sealing layer is formed on the surface of the insulating coating layer.

3. The coil device according to claim 1 or 2, wherein: The magnetic powder contained in the resin-rich layer is composed of soft magnetic metal.

4. The coil device according to claim 1 or 2, wherein: The resin-rich layer contains the magnetic powder having a particle size larger than the thickness of the insulating coating layer.

5. The coil device according to claim 1 or 2, wherein: The magnetic powder contained in the resin-rich layer is metallic magnetic powder. The resin-rich layer contains the metal magnetic powder having a particle size smaller than the thickness of the insulating coating layer.

6. The coil device according to claim 1 or 2, wherein: The electric wire is composed of a flat wire.

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