Coil device and method for manufacturing coil device

Abstract

[Problem] To provide a coil device for controlling leakage inductance within a predetermined range. [Solution] This coil device has a first conductor extending in a predetermined direction, a second conductor disposed inside the first conductor and at least partially extending along the first conductor, and an inter-conductor insulation part positioned between the first conductor and the second conductor. The inter-conductor insulation part has, in the vicinity of an installation opposing surface, a magnetic flux control part capable of controlling leakage inductance within a predetermined range.

Description

Coil device and method for manufacturing the same

[0001] The present disclosure relates to a coil device and a method for manufacturing a coil device.

[0002] The leakage inductance of a coil device may affect other coils or wiring patterns, or may cause noise. For example, the coil device described in Patent Document 1 is known as a coil device that can reduce leakage inductance. The coil device described in Patent Document 1 reduces leakage inductance by forming a first winding and a second winding on a substrate and folding and overlapping the substrate to sandwich the first winding and the second winding.

[0003] Meanwhile, advances in semiconductor and computer technologies have led to lower voltage and higher current in semiconductor elements, and coil devices used in power supply circuits, for example, are now required to have load responsiveness that allows them to stably output a constant voltage even under driving conditions where the large current load changes suddenly.Coil devices through which such large currents flow also tend to have increased leakage flux.

[0004] Japanese Patent Application Publication No. 5-243057

[0005] An object of the present disclosure is to provide a coil device capable of controlling leakage inductance in a minute region and a method for manufacturing the same.

[0006] A coil device according to one embodiment of the present disclosure includes: a first conductor extending in a predetermined direction; a second conductor arranged inside the first conductor, at least a portion of which extends along the first conductor; and an inter-conductor insulation portion located between the first conductor and the second conductor, wherein the inter-conductor insulation portion has a magnetic flux control portion near a mounting opposing surface that is capable of controlling leakage inductance within a predetermined range.

[0007] Furthermore, a method for manufacturing a coil device according to one embodiment of the present disclosure includes: preparing a first conductor and a second conductor, at least a portion of which can extend along the first conductor; arranging the second conductor inside the first conductor so that at least a portion of the second conductor extends along the first conductor; forming an inter-conductor insulation portion between the first conductor and the second conductor; and the inter-conductor insulation portion having a magnetic flux control portion near the opposing mounting surface, which is capable of controlling leakage inductance within a predetermined range.

[0008] In a coil device having such characteristics and a coil device manufactured by a method for manufacturing a coil device, an inter-conductor insulation portion is formed between the first conductor and the second conductor, and the inter-conductor insulation portion has a magnetic flux control portion near the mounting opposing surface that can control the leakage inductance within a predetermined range.Therefore, the leakage inductance near the mounting opposing surface between the first conductor and the second conductor can be controlled in a small area, and good coil characteristics can be obtained.

[0009] FIG. 1A is a see-through perspective view of a coil device according to a first embodiment of the present disclosure, as seen from diagonally above. FIG. 1B is a perspective view of the coil device shown in FIG. 1A, as seen from the mounting opposing surface (bottom surface). FIG. 1C is a top view of the coil device shown in FIG. 1A. FIG. 1D is a bottom view of the coil device shown in FIG. 1A. FIG. 1E is a cross-sectional view of the coil device shown in FIG. 1A, taken along line E-E in FIG. 1A. FIG. 1F is an enlarged cross-sectional view of regions F1 and F2 in FIG. 1E. FIG. 1G is a cross-sectional view of the coil device shown in FIG. 1A, taken along line G-G in FIG. 1A. FIG. 2A is a flowchart illustrating an example of a method for manufacturing a coil device according to the present disclosure. FIG. 2B is a first diagram illustrating a method for manufacturing the coil device shown in FIG. 2A. FIG. 2C is a second diagram illustrating a method for manufacturing the coil device shown in FIG. 2A. FIG. 2D is a third diagram illustrating a method for manufacturing the coil device shown in FIG. 2A. FIG. 2E is a fourth diagram illustrating a method for manufacturing the coil device shown in FIG. 2A. 3A, 3B, and 3C are diagrams illustrating a first, a second, and a third modified example of a coil device according to the present disclosure;

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The embodiments described below are examples for explaining the present disclosure, and the present disclosure is not limited to the following embodiments. Various components according to the following embodiments, such as numerical values, shapes, materials, manufacturing processes, etc., can be modified or changed within the scope of technical problems. Furthermore, the contents shown in the drawings are merely shown schematically and exemplarily to facilitate understanding of the present disclosure, and the appearance, dimensional ratios, etc. may differ from the actual product.

[0011] First Embodiment As a first embodiment of the present disclosure, a coil device 1 suitable for use as a coupling coil in the power supply circuits of various electrical devices will be described with reference to FIGS. 1A to 1G.

[0012] As shown in FIG. 1A, the coil device 1 is an electronic component having a substantially rectangular parallelepiped (hexahedral) shape, having a top surface 1a, a bottom surface 1b as a mounting-facing surface that is joined to a mounting surface of a circuit board or the like and electrically connected to an external circuit, and first to fourth side surfaces 1c1...1c4 that connect the top surface 1a and the bottom surface (mounting-facing surface) 1b.

[0013] In this disclosure, the direction in which the fourth side surface 1c4 and the second side surface 1c2 face each other is defined as the X-axis direction, the direction in which the first side surface 1c1 and the third side surface 1c3 face each other is defined as the Y-axis direction, and the direction in which the bottom surface 1b and the top surface 1a face each other is defined as the Z-axis direction. The X-axis, Y-axis, and Z-axis are perpendicular to each other. The directions from the fourth side surface 1c4 toward the second side surface 1c2, the first side surface 1c1 toward the third side surface 1c3, and the bottom surface 1b toward the top surface 1a are defined as the positive directions of the X, Y, and Z axes, respectively, and the directions opposite to the positive directions of each axis are defined as the negative directions of the X, Y, and Z axes. The positive Z-axis direction may also be referred to as the upward direction or upward facing, and the negative Z-axis direction may also be referred to as the downward direction or downward facing.

[0014] The size of the coil device 1 is not particularly limited, but for example, the length (width) of the coil device 1 in the X-axis direction is 1 mm to 40 mm, the length (length / depth) of the coil device 1 in the Y-axis direction is 1 mm to 100 mm, and the length (height) of the coil device 1 in the Z-axis direction is 0.5 mm to 20 mm.

[0015] As shown in Figure 1A, the coil device 1 has a plurality of (four in this embodiment) conductor assemblies 10...10 arranged in parallel along the Y-axis direction, and an outer casing portion 50 that covers the plurality of conductor assemblies 10...10.

[0016] 1E, each conductor assembly 10 has a first conductor 11 that has a U-shaped planar shape (shape on the X-Z plane) when viewed from the Y-axis direction, a second conductor 23 that has the same U-shape as the first conductor 11, is arranged inside the first conductor 11, and extends mostly along the first conductor 11, and a conductor assembly covering portion 30 that covers the first conductor 11 and the second conductor 23. Either the first conductor 11 or the second conductor 23 functions as a primary coil, and the other functions as a secondary coil.

[0017] 1E and 1G , the first conductor 11 as a vertically elongated flat conductor plate has an outer main surface 112 that faces the upper surface of the coil device 1, an inner main surface 113 that faces the opposite direction from the outer main surface 112, side surfaces 114, 114 connecting the outer main surface 112 and the inner main surface 113 on both sides in the width direction (short direction) of the vertically elongated flat plate, and end surfaces 141, 141 connecting the outer main surface 112 and the inner main surface 113 on both sides in the extension direction (longitudinal direction) of the vertically elongated flat plate.

[0018] The material of the conductive plate constituting the first conductor 11 is not particularly limited as long as it is a conductive material, but examples include good conductors such as copper, copper alloys, silver, and nickel. For example, the thickness of the first conductor 11 is 0.1 mm to 2.5 mm, the width of the first conductor 11 is 0.1 mm to 5 mm, and the length of the entire plate of the first conductor 11 in the longitudinal direction is 1 mm to 100 mm.

[0019] The first conductor 11 has a central region 120 and end-side regions 130, 130 that are portions on both sides of the central region 120 in the extension direction of the first conductor 11. The central region 120 is arranged in a form extending in the X-direction along the top surface 1a of the coil device 1, and at bent portions 123, 123 at both ends of the central region 120, the extension direction is changed by approximately 90 degrees downward in the Z-axis direction and is continuous with the end-side regions 130, 130. The end-side regions 130, 130 are arranged in a form extending in the Z-axis direction along the side surface 1c of the coil device 1.

[0020] The end side regions 130, 130 of the first conductor 11 are formed in a form that extends directly to the bottom surface (facing mounting surface) 1b of the coil device 1, and the end faces 141, 141 at the extreme ends are exposed to the outside at the bottom surface 1b, forming joinable portions 150, 150 that can be electrically connected to an external circuit.

[0021] As shown in FIG. 1E, the first conductor 11 is covered by the conductor assembly covering portion 30 over the entire longitudinal direction, but only the end faces 141, 141 of both end portions 140, 140 are not covered by the conductor assembly covering portion 30, and these portions are designated as joinable portions 150, 150.

[0022] Electrodes (not shown) may be electrically and mechanically connected to the end faces 141, 141 of the joinable portions 150, 150. In this case, the electrodes may be formed by attaching an electrode member to the mounting-facing surface (bottom surface) 1b of the coil device 1, or by plating or the like on the mounting-facing surface (bottom surface) 1b including the exposed end faces 141, 141 of the first conductor 11. Alternatively, electrodes as separate components may not be formed on the end faces 141, 141 (joinable portions 150, 150) of the first conductor 11, and the end faces 141, 141 (joinable portions 150, 150) of the first conductor 11 may be directly electrically and mechanically connected to the mounting surface by a joining member such as solder or a conductive adhesive.

[0023] One joinable portion 150, which is one end face 141, functions as an input terminal, and the other joinable portion 150, which is the other end face 141, functions as an output terminal, and the two end side regions 130, 130 and the central region 120 between both end faces 141, 141 connect the input terminal and the output terminal. It is possible to arbitrarily set which end face 141 (joinable portion 150) is to be the input terminal or the output terminal.

[0024] The first conductor 11 is formed by, for example, machining (bending) such a conductor plate, but the method for forming the first conductor 11 is not limited to this. In the first conductor 11 of this embodiment, as shown in Fig. 1E, its length (width) in the X-axis direction is longer than its length (height) in the Z-axis direction, and it is formed in an overall flat shape. However, the first conductor 11 may also be formed in a tall shape in which its length (height) in the Z-axis direction is longer than its length (width) in the X-axis direction.

[0025] The first conductors 11 may have a plating layer formed around the periphery of the conductor plate. The plating layer may be a single layer or multiple layers, and may be formed from a metal plating layer such as Cu plating, Ni plating, Sn plating, Ag plating, Ni-Sn plating, Cu-Ni-Sn plating, Ni-Au plating, or Au plating. The plating layer is formed by, for example, electroplating or electroless plating on the surface of the conductor plate serving as the base material of the first conductors 11. The thickness of the plating layer is not particularly limited, but may be preferably 0.05 μm to 30 μm.

[0026] The second conductor 23 is made of an elongated flat (vertical flat) conductive plate, similar to the first conductor 11. As shown in Figures 1E and 1G , the second conductor 23 as a vertical flat conductive plate has an outer main surface 212 that faces the upper surface direction in the coil device 1, an inner main surface 213 that faces the opposite direction to the outer main surface 212, side surfaces 214, 214 that connect the outer main surface 212 and the inner main surface 213 on both sides in the width direction (short direction) of the vertical flat plate, and end surfaces 241, 241 that connect the outer main surface 212 and the inner main surface 213 on both sides in the extension direction (longitudinal direction) of the vertical flat plate.

[0027] The material of the conductive plate constituting the second conductor 23 can be, for example, a good conductor such as copper, copper alloy, silver, or nickel, but is not particularly limited as long as it is a conductive material. For example, the thickness of the second conductor 23 is 0.1 mm to 2.5 mm, the width of the second conductor 23 is 0.1 mm to 5 mm, and the length of the entire plate of the second conductor 23 in the longitudinal direction is 1 mm to 100 mm. The thickness, width, and length of the second conductor 23 may be approximately the same as those of the first conductor 11, or may be larger (thicker, wider, longer) or smaller (thinner, narrower, shorter) than the first conductor 11.

[0028] 1E, the second conductor 23 has a central region 220 and end regions 230, 230 which are portions on both sides of the central region 220 in the extension direction of the second conductor 23. The central region 220 is disposed inside the first conductor 11 at a predetermined interval from the central region 120 of the first conductor 11 and extends along the central region 120 of the first conductor 11.

[0029] Bent portions 223, 223 that change the extension direction of the central region 220 downward in the Z-axis direction by approximately 90 degrees are arranged on both sides of the extension direction, and end side regions 230, 230 are continuous below the bent portions 223, 223. The bent portions 223, 223 of the second conductor 23 are arranged inside the bent portions 123, 123 of the first conductor 11 and along the bent portions 123, 123 of the first conductor 11 at a predetermined interval from the bent portions 123, 123 of the first conductor 11. Furthermore, the end side regions 230, 230 of the second conductor 23 are arranged inside the end side regions 130, 130 of the first conductor 11 and along the end side regions 130, 130 of the first conductor 11 at a predetermined interval from the end side regions 130, 130 of the first conductor 11.

[0030] In the end-side regions 230, 230 of the second conductor 23, bent portions 234, 234 whose extension direction changes approximately 90 degrees inward in the X-axis direction are arranged in positions near the mounting opposing surface (bottom surface) 1b of the coil device 1, and end portions 240, 240 of the second conductor 23 are continuous with the inner side of the bent portions 234, 234 in the X-axis direction. The end portions 240, 240 may be portions of the second conductor 23 further distal than the bent portions 234, 234, and are formed in inner bent portions 243, 243 extending inward along the mounting opposing surface (bottom surface) 1b of the coil device 1. The inner bent portions 243, 243 are exposed to the outside at the mounting opposing surface (bottom surface) 1b and form joinable portions 250, 250 that can be electrically connected to an external circuit.

[0031] As shown in FIG. 1E, the entire length of the second conductor 23 is covered by the conductor assembly covering portion 30, but only the outer main surfaces 212 of the ends 240 at both ends are not covered by the conductor assembly covering portion 30, and these portions are designated as joinable portions 250, 250.

[0032] An electrode (not shown) may be electrically and mechanically connected to the end portions 240, 240 of the joinable portions 250, 250. In this case, the electrode may be an electrode member attached to the mounting surface (bottom surface) 1b of the coil device 1, or may be formed by plating or the like on the mounting surface (bottom surface) 1b including the exposed end portions 240, 240 of the second conductor 23. Alternatively, no electrode as a separate component is formed on the end portions 240, 240 (joinable portions 250, 250) of the second conductor 23, and the end portions 240, 240 (joinable portions 250, 250) of the second conductor 23 may be directly electrically and mechanically connected to the mounting surface by a joining member such as solder or a conductive adhesive.

[0033] One joinable portion 250, which is one end portion 240, functions as an input terminal, and the other joinable portion 250, which is the other end portion 240, functions as an output terminal, and the two end side regions 230, 230 and the central region 220 between the end portions 240, 240 connect the input terminal and the output terminal. It is possible to arbitrarily set which end portion 240 (joinable portion 250) is to be the input terminal or the output terminal.

[0034] The second conductor 23 is formed by, for example, machining (bending) such a conductor plate, but the method for forming the second conductor 23 is not limited to this. In the second conductor 23 of this embodiment, as shown in Fig. 1E, its length (width) in the X-axis direction is longer than its length (height) in the Z-axis direction, and it is formed in an overall flat shape. However, the second conductor 23 may also be formed in a tall shape in which its length (height) in the Z-axis direction is longer than its length (width) in the X-axis direction.

[0035] The second conductors 23 may have a plating layer formed around the periphery of the conductor plate. The plating layer may be a single layer or multiple layers, and may be formed from a metal plating layer such as Cu plating, Ni plating, Sn plating, Ag plating, Ni-Sn plating, Cu-Ni-Sn plating, Ni-Au plating, or Au plating. The plating layer is formed by, for example, electroplating or electroless plating on the surface of the conductor plate serving as the base material of the second conductors 23. The thickness of the plating layer is not particularly limited, but may be preferably 0.05 μm to 30 μm.

[0036] In relation to the shape of the first conductor 11, in this embodiment, the second conductor 23 is slightly smaller in size in the X-Y plane, has substantially the same shape as the first conductor 11, and is disposed inside the first conductor 11, as shown in FIG. 1E . The second conductor 23 is disposed substantially parallel to the first conductor 11, except for the region near the mounting surface (bottom surface) 1b. That is, the distance between the central region 120 of the first conductor 11 and the opposing central region 220 of the second conductor 23, and the distance between the bent portions 123, 123 of the first conductor 11 and the opposing bent portions 223, 223 of the second conductor 23, are substantially the same. Furthermore, the distances between the end-side regions 130, 130 of the first conductor 11 and the respective end-side regions 230, 230 of the second conductor 23 are substantially the same, except for the region near the mounting surface (bottom surface) 1b. In the region where the first conductor 11 and the second conductor 23 are arranged approximately parallel (parallel extension region), the distance between the first conductor 11 and the second conductor 23 is, for example, 5 μm or more in order to ensure insulation, and may be 10 μm to 2 mm.

[0037] In the region near the mounting surface (bottom surface) 1b, the second conductor 23 has ends 240, 240 bent inward in the X-axis direction via bent portions 234, 234, and the gap between the second conductor 23 and the first conductor 11 is widened.

[0038] In the present disclosure, the shapes of the first conductor 11 and the second conductor 23 do not need to be the same, as long as at least a portion of the second conductor 23 extends along the inside of the first conductor 11. Furthermore, as shown in Fig. 1G, the width (length in the Y-axis direction) of the second conductor 23 is approximately the same as the width of the first conductor 11 in this embodiment, but may be wider (longer) or narrower (shorter) than the width of the first conductor 11.

[0039] The conductor assembly covering portion 30 has an external shape that is approximately rectangular parallelepiped, and is formed around the first conductor 11 and the second conductor 23 so as to cover the first conductor 11 and the second conductor 23 in areas other than the mounting-facing surface (bottom surface) 1b of the coil device 1. The conductor assembly covering portion 30 is formed from an insulating material, and ensures insulation between the first conductor 11 and the first conductor 12 (prevents short circuits), as well as insulation between the first conductor 11 and the outside of the coil device 1 or between the second conductor 23 and the outside of the coil device 1 in areas other than the joinable portions 150, 150 and the joinable portions 250, 250 (prevents short circuits).

[0040] The conductor assembly covering portion 30 includes an inter-conductor insulating portion 31 filled between the first conductor 11 and the second conductor 23, an outer insulating portion 32 covering at least the outer main surface 112 of the first conductor 11, and an inner insulating portion 33 covering at least the inner main surface 213 of the second conductor 23.

[0041] The material forming the conductor assembly covering portion 30, i.e., the material forming the inter-conductor insulating portion 31, the outer insulating portion 32, and the inner insulating portion 33, is not particularly limited, but examples thereof include resin materials such as polyester, polyesterimide, polyamide, polyamideimide, polyurethane, epoxy, epoxy-modified acrylic resin, etc. The materials forming the inter-conductor insulating portion 31, the outer insulating portion 32, and the inner insulating portion 33 may be the same material or different materials.

[0042] The inter-conductor insulation 31 is formed from an insulating material filled at least between the first conductor 11 and the second conductor 23, and serves to provide good insulation between the first conductor 11 and the second conductor 23. As shown in Fig. 1E, the inter-conductor insulation 31 is formed at least between the inner main surface 113 of the first conductor 11 and the outer main surface 212 of the second conductor 23 over the entire area where the first conductor 11 and the second conductor 23 face each other. The inter-conductor insulation 31 is in close contact with the inner main surface 113 of the first conductor 11 and the outer main surface 212 of the second conductor 23, with no gap formed between them.

[0043] By connecting the first conductor 11 and the second conductor 23 via the inter-conductor insulation portion 31, the leakage magnetic flux (leakage inductance) can be reduced and the magnetic coupling between the first conductor 11 and the second conductor 23 can be enhanced.

[0044] 1F , in the inter-conductor insulation 31, inter-joinable portion regions 1d, 1d between the first conductor 11 and the second conductor 23 near the opposing mounting surface (bottom surface) 1b of the coil device 1, which are between one and the other joinable portions 150, 150 of the first conductor 11 and one and the other joinable portions 250, 250 of the second conductor 23 adjacent to the joinable portions 150, 150, are formed so as to be approximately flush with the joinable portions 150 of the first conductor 11 and the joinable portions 250 of the second conductor 23, respectively. Note that being approximately flush means that the distance along the Z-axis direction between the inter-joinable portion regions 1d, the joinable portions 150 of the first conductor 11, and the joinable portions 250 of the second conductor 23 is at most 50% of the thickness WA of the inter-conductor insulation 31. The distance along the Z-axis direction between the inter-joinable portion region 1d, the joinable portion 150 of the first conductor 11, and the joinable portion 250 of the second conductor 23 may be within 1 mm, within 5 μm, or within 1 μm.

[0045] As described above, the first conductor 11 and the second conductor 23 are substantially parallel except for the region near the opposing mounting surface (bottom surface) 1b. Meanwhile, near the opposing mounting surface (bottom surface) 1b, the end-side region 230 of the second conductor 23 is bent inward in the X-axis direction via bent portions 234, 234, thereby widening the gap between the first conductor 11 and the second conductor 23. As shown in FIG. 1F , the inter-conductor insulating portion 31 includes a conductor gap widening portion 35, which is a portion filled with an insulating material in the region near the opposing mounting surface (bottom surface) 1b where the gap between the first conductor 11 and the second conductor 23 is widened.

[0046] 1F , the conductor spacing expansion portion 35 is a portion where the ratio WB / WA of the thickness WB of the inter-conductor insulation portion 31 at the mounting surface (bottom surface) 1b to the thickness WA (the distance between the first conductor 11 and the second conductor 23) of the inter-conductor insulation portion 31 in the parallel extending region where the first conductor 11 and the second conductor 23 are arranged substantially parallel to each other is within a predetermined reference range, an insulating material is filled between the first conductor 11 and the second conductor 23, and the inter-joinable portion region 1d at the mounting surface (bottom surface) 1b is formed substantially flush with the joinable portion 150 of the first conductor 11 and the joinable portion 250 of the second conductor 23. The reference range for the ratio WB / WA may be, for example, 1.5 or more, 2 or more, 3 or more, or a range of 3 to 5.

[0047] The thickness WA of the inter-conductor insulating portion 31 (the distance between the first conductor 11 and the second conductor 23) in the parallel extending region where the first conductor 11 and the second conductor 23 are arranged approximately parallel to each other is, for example, 5 μm or more, and may be 10 μm to 2 mm.

[0048] Near the mounting opposing surface (bottom surface) 1b, a portion is formed where the distance between the joinable portion 150 of the first conductor 11 and the joinable portion 250 of the second conductor 23 is increased, and an insulating material is placed in this portion, i.e., by forming an expanded conductor spacing portion 35, the leakage magnetic flux (leakage inductance) in the region 1d between the joinable portions can be further reduced, and the magnetic coupling between the first conductor 11 and the second conductor 23 can be further enhanced.

[0049] The thickness WB of the inter-conductor insulation 31 on the opposing mounting surface (bottom surface) 1b can be determined by the radius of curvature R of the bent portion 234 of the second conductor 23. That is, by adjusting the radius of curvature R of the bent portion 234 of the second conductor 23, it is possible to adjust the size of the expanded conductor spacing portion 35 of the inter-conductor insulation 31, in other words, the arrangement of the insulating material filled in the inter-joinable portion region 1d between the joinable portion 150 of the first conductor 11 and the joinable portion 250 of the second conductor 23. Therefore, by adjusting the radius of curvature R of the bent portion 234 of the second conductor 23, it is possible to control the leakage magnetic flux (leakage inductance) from the inter-joinable portion region 1d within a predetermined range. Therefore, the expanded conductor spacing portion 35 functions as a magnetic flux control portion.

[0050] The radius of curvature R of the bent portion 234 of the second conductor 23 may be set appropriately depending on the size of the coil device 1, and is, for example, 0.02 mm to 1.5 mm.

[0051] On the opposing mounting surface (bottom surface) 1b, an inter-conductor insulation portion 31 is formed in the region (inter-joinable portion region 1d) between the joinable portion 150 of the first conductor 11 and the joinable portion 250 of the second conductor 23.This makes it possible to prevent joining materials such as solder from creeping up from the inter-joinable portion region 1d to the end side regions 130, 230 of the first conductor 11 and the second conductor 23 when the coil device 1 is mounted on a mounting surface such as a substrate, and ensures good insulation between the first conductor 11 and the second conductor 23 even when in operation after mounting.

[0052] 1E and 1G, the outer insulating portion 32 is made of an insulating material and covers at least the outer main surface 112 of the first conductor 11 over the entire area in which the first conductor 11 extends. The outer insulating portion 32 may also cover the side surfaces 114, 114 (see FIG. 1G) of the first conductor 11. The outer insulating portion 32 serves to effectively insulate the first conductor 11 from the outside of the conductor assembly 10. The outer insulating portion 32 is in close contact with the outer main surface 112 of the first conductor 11, with no gap formed between the outer insulating portion 32 and the outer main surface 112.

[0053] The outer insulating portion 32 is formed of an insulating material such as resin, but may contain a soft magnetic material as long as the insulating properties are ensured. By including a soft magnetic material in the outer insulating portion 32, it is possible to improve the magnetic properties.

[0054] The inner insulating portion 33 is formed of an insulating material and covers the inner main surface 213 of the second conductor 23 over the entire area in which the second conductor 23 extends, as shown in Figures 1E and 1G. The inner insulating portion 33 may also cover the side surfaces 214, 214 (see Figure 1G) of the second conductor 23. The inner insulating portion 33 serves to effectively insulate the second conductor 23 from the central core portion 53 of the exterior body portion 50, which is formed further inside the second conductor 23. The inner insulating portion 33 is in close contact with the inner main surface 213 of the second conductor 23, and no gap is formed between the inner insulating portion 33 and the inner main surface 213.

[0055] The inner insulating portion 33 is formed of an insulating material such as resin, but may contain a soft magnetic material within the range that ensures insulation, similar to the outer insulating portion 32. When the inner insulating portion 33 contains a soft magnetic material, it is possible to improve the magnetic properties.

[0056] The conductor assembly covering 30, which includes the inter-conductor insulating portion 31, the outer insulating portion 32, and the inner insulating portion 33, may include other insulating portions disposed in areas other than those considered (defined) as the inter-conductor insulating portion 31, the outer insulating portion 32, and the inner insulating portion 33. The other insulating portions may include portions covering the side surfaces 114, 114 of the first conductor 11 and the side surfaces 214, 214 of the second conductor 23, as shown in FIG. 1G. For example, if the inter-conductor insulating portion 31, the outer insulating portion 32, the inner insulating portion 33, and the "other insulating portions" are formed of different materials, the conductor assembly covering 30 may be divided into regions in this manner, and insulating portions may be formed in each region using an appropriate material.

[0057] The inter-conductor insulating portion 31, the outer insulating portion 32, the inner insulating portion 33, and the "other insulating portions" according to the present disclosure have a structure formed by packing insulating material into a space without gaps. Generally, so-called "voids" filled with air or some other gas may have insulating properties, but such "voids" may be excluded from the components that make up the above-mentioned "insulating portions" according to the present disclosure. The above-mentioned "insulating portions" according to the present disclosure have higher insulating properties and superior moisture resistance compared to voids as insulating portions.

[0058] The exterior body 50 is a member that integrally covers the plurality of first conductors 11 and forms the outer shape of the coil device 1. As shown in Fig. 1A, the exterior body 50 has an upper surface 51a, a bottom surface (lower surface) 51b that faces the upper surface 51a, and first to fourth side surfaces 51c1 to 51c4 that connect the bottom surface 51b and the upper surface 51a. The outer shape of the exterior body 50 is a hexahedron that is a substantially rectangular parallelepiped, but is not limited to a hexahedron and may be another polyhedron such as an octahedron, a columnar body such as a cylinder, or a three-dimensional shape in which the lower surface and the upper surface are not congruent, such as a truncated cone.

[0059] The first to fourth side surfaces 1c1 to 1c4 of the coil device 1 are configured by the first to fourth side surfaces 51c1 to 51c4 of the exterior body part 50. In other words, the first to fourth side surfaces 1c1 to 1c4 of the coil device 1 are the same as the first to fourth side surfaces 51c1 to 51c4 of the exterior body part 50.

[0060] 1C , the upper surface 1a of the coil device 1 includes not only the upper surface 51a of the exterior body part 50 but also the upper surface 32a of the outer insulating part 32 of the conductor assembly 10. In this way, by exposing the upper surface 32a of the outer insulating part 32 of the conductor assembly covering part 30 to the outside from the upper surface 51a of the exterior body part 50, i.e., from the upper surface 1a of the coil device 1, it is possible to efficiently dissipate heat generated around the conductor assembly 10 to the outside of the coil device 1.

[0061] In addition, the mounting opposing surface (bottom surface) 1b of the coil device 1 is configured to include, in addition to the bottom surface 51b of the outer casing portion 50, joinable portions 150, 250 of the first conductor 11 and the second conductor 23, or electrodes (not shown) formed on the joinable portions 150, 250.

[0062] The exterior body portion 50 has a peripheral portion 52, a core portion 53, and a conductor assembly inter-portion 54. As shown in Fig. 1C , the peripheral portion 52 is a portion that forms the outer shape of the coil device 1. As shown in Fig. 1A , the core portion 53 is a portion of the exterior body portion 50 that penetrates into and fills the inside of the second conductor 23 of the conductor assembly 10.

[0063] As shown in FIG. 1A , the conductor assembly inter-sections 54 are spaces between the multiple conductor assembly coverings 30 arranged in parallel in the Y-axis direction. In the coil device 1 according to the present disclosure, a resin-rich layer may be formed near the interface between the primary molding for forming the conductor assembly covering 30 and the secondary molding for forming the exterior body 50. That is, the coil device 1 may have a resin-rich layer at the interface between the outer insulating section 32 and the exterior body 50. The coil device 1 may have a resin-rich layer at the interface between the inner insulating section 33 and the exterior body 50. In the outer insulating section 32, the region that interfaces with the exterior body 50 has a higher resin content than the region other than the interface with the exterior body 50. Furthermore, in the exterior body 50, the region that interfaces with the outer insulating section 32 has a higher resin content than the region other than the interface with the outer insulating section 32. The same applies to the inner insulating section. Because this resin-rich layer has a low magnetic particle content and high insulating properties, a coil device 1 having such a configuration ensures sufficiently high insulation between the multiple conductor assemblies 10. The content of the metal elements (e.g., Fe) constituting the magnetic particles and the elements (e.g., C) constituting the resin in the resin-rich layer can be determined based on the results of simple quantitative analysis using cross-sectional EDS. In the resin-rich layer, the weight proportion of the metal elements constituting the magnetic particles is lower and the weight proportion of the elements constituting the resin is higher than in other areas (e.g., near the surface of the exterior body 50). The thickness of the resin-rich layer is not particularly limited, but may be, for example, 1 μm to 200 μm, 1 μm to 50 μm, or 1 μm to 10 μm. The difference between the content of the elements (e.g., C) constituting the resin in the resin-rich layer and the content of the elements (e.g., C) constituting the resin in areas other than the resin-rich layer is not particularly limited, but may be, for example, 0.1 wt % to 8.0 wt %, or 0.5 wt % to 1.0 wt %.

[0064] The exterior body 50 is formed of a sheathing material containing magnetic particles and resin, and may be formed using a magnetic material with relatively high magnetic permeability. In this embodiment, the first conductor 11 and the second conductor 23 are covered with the outer insulating portion 32 and the inner insulating portion 33, ensuring insulation regardless of the exterior body 50. This allows the exterior body 50 to be made of an Fe-based soft magnetic material. As a result, the coil device 1 having such an exterior body 50 has high voltage resistance and can handle large current loads. The exterior body 50 may be made from a material such as Ni-Zn ferrite, Mn-Zn ferrite, or a magnetic powder made of a metal magnetic material, which is molded and sintered.

[0065] The particle size of the magnetic particles forming the exterior body 50 is not particularly limited, but is, for example, 1 μm to 50 μm. The resin forming the exterior body 50 is not particularly limited, but is, for example, a thermosetting resin such as an epoxy resin or a phenolic resin. The relative permeability of the exterior body 50 is not particularly limited, but is, for example, 1 to 20,000.

[0066] Although not shown, the coil device 1 according to the present disclosure may include terminal electrodes. The electrodes are conductive members connected to the joinable portions 150 of the first conductor 11 and the joinable portions 250 of the second conductor 23. The terminal electrodes are formed, for example, by machining a conductive metal plate, but the method for forming the terminal electrodes is not particularly limited. The material of the terminal electrodes is not particularly limited as long as it is a conductive metal material, and examples thereof include iron, nickel, copper, silver, etc., or alloys containing these. In addition, a metal coating of Ni, Sn, Cu, etc. may be formed on the surface of the terminal electrodes.

[0067] Instead of metal terminals, terminal electrodes may be formed on the exterior body 50 by plating. In this case, the terminal electrodes are formed, for example, by a laminated electrode film of a base electrode film and a plating film formed on the base electrode film. The base electrode film is not particularly limited, but may be a conductive paste film containing a metal such as Sn, Ag, Ni, or Cu, or an alloy thereof. The plating film is not particularly limited, but may be a metal such as Sn, Au, Ni, Pt, Ag, or Pd, or an alloy thereof.

[0068] An example of a method for manufacturing a coil device according to the present disclosure will be described with reference to Figures 2A to 2E. Figure 2A is a flowchart showing an example of a method for manufacturing a coil device 1 according to the present disclosure.

[0069] 2B , the manufacturing process of the coil device 1 first manufactures the first conductor 11 and the second conductor 23 (step S1). As a specific example, a long, narrow flat plate (vertically elongated flat plate) for the first conductor 11 having a predetermined length, width, and thickness is machined (bending) to form bent portions 123, 123, thereby manufacturing the first conductor 11 having the central region 120, bent portions 123, 123, and end-side regions 130, 130.

[0070] Furthermore, a long, narrow flat plate (vertically elongated flat plate) for the second conductor 23 having a predetermined length, width, and thickness is machined (bent) to form bent portions 223, 223 and bent portions 234, 234, thereby manufacturing the second conductor 23 having a central region 220, bent portions 223, 223, end side regions 230, 230, bent portions 234, 234, and end portions 240, 240. At this time, the bent portions 234, 234 of the second conductor 23 are adjusted to have a desired radius of curvature R. The radius of curvature R can be easily adjusted using a jig during the bending process.

[0071] 2C , the first conductors 11 and the second conductors 23 are assembled on an upper mold 71 (step S2). That is, with the second conductor 22 arranged inside the first conductor 11, the first conductors 11 and the second conductors 23 are placed on the upper mold 71 using a support (for example, a carrier, a film, etc.) 73 for temporary fixation.

[0072] A center core protection member 72 may be further disposed inside the second conductor 22. The center core protection member 72 is a member for forming an opening (a space to be filled with the exterior body 50 later) inside the second conductor 22 where the conductor assembly cover 30 is not formed; in other words, a member for defining the area where the conductor assembly cover 30 is formed. The center core protection member 72 may be configured as a convex portion formed on the upper mold 71, or may be configured to be disposed inside the second conductor 23 and installed on the upper mold 71 by a support 73, similar to the first conductor 11 and the second conductor 23. However, if an opening (a space to be filled with the exterior body 50 later) is not formed inside the second conductor 22 in the conductor assembly 10, the center core protection member 72 may not be used.

[0073] Instead of the support 73, the first conductors 11, the second conductors 23 and the core protection member 72 may be held to the upper mold 71 using an adhesive or the like, or by mechanical or magnetic means.

[0074] For the sake of explanation, FIG. 2C shows only one first conductor 11 and one second conductor 23, but multiple sets of first conductor 11, first conductor 12 and core protection member 72 may be placed on the upper mold 71.

[0075] After the first conductors 11, 12 and core protection member 72 are assembled in the upper mold 71, they are sealed with the conductor assembly covering portion 30 to form the conductor assembly 10 (step S3).

[0076] First, as shown in FIG. 2D , a lower mold 75 is formed with a conductor assembly covering pot portion (recess) 76 shaped to fit the outer shape of the conductor assembly 10, and a conductor assembly covering material 83 is injected into the conductor assembly covering pot portion (recess) 76. The conductor assembly covering material 83 may be any insulating material with low magnetic permeability, and specifically, a resin material such as a thermoplastic resin or a thermosetting resin may be used. The conductor assembly covering material 83 may also include a soft magnetic material. The conductor assembly covering material 83 may be, for example, a material that is granular or particulate at room temperature and becomes fluid (e.g., a highly viscous liquid) when heated (e.g., at 80° C. or higher).

[0077] The conductor assembly covering material 83 is poured into the conductor assembly covering pot portion (recess) 76 of the lower mold 75, and then molded. The upper mold 71 and the lower mold 75 are heated to a predetermined mold temperature, and the upper mold 71 is turned upside down from the state shown in FIG. 2C as shown in FIG. 2D , i.e., the first conductor 11, the second conductor 23, and the center core protection member 72 are suspended. The upper mold 71 and the lower mold 75 are then brought close to each other, and the first conductor 11, the second conductor 23, and the center core protection member 72 are inserted into the conductor assembly covering pot portion (recess) 76, respectively.

[0078] Furthermore, the lower mold 75 is moved toward the upper mold 71, and the conductor assembly covering material 83 is filled into each conductor assembly covering pot portion (recess) 76, and the conductor assembly covering material 83 is molded at a predetermined temperature for a predetermined time.

[0079] After molding the conductor assembly covering material 83 at a predetermined temperature for a predetermined time, the upper mold 71 is separated from the lower mold 75. As a result, a molded body is formed on the upper mold 71 in which the first conductors 11 and the second conductors 23 are covered with the conductor assembly covering 30 and the core protection member 72 is disposed inside the second conductor 23. The individual molded bodies are separated and released from the upper mold 71, and the core protection member 72 is separated and removed. As a result, the conductor assembly 10 is formed.

[0080] After the conductor assemblies 10 are formed, an exterior body 50 is formed to integrally cover the plurality of conductor assemblies 10 (step S4). To form the exterior body 50, first, as shown in FIG. 2E , a plurality of conductor assemblies 10 to be housed in one coil device 1 are arranged on an upper mold 71 via supports 73, and the upper mold 71 is then inverted upside down so that the conductor assemblies 10 are suspended. A lower mold 75 is formed with a plurality of exterior body-forming pot portions (recesses) 77 shaped to fit the outer shape of the coil device 1, and an exterior body material 85 is poured into the exterior body-forming pot portions (recesses) 77. The exterior body material 85 is a material containing magnetic particles and a resin. Specifically, a composite magnetic material containing a binder such as a thermoplastic resin or a thermosetting resin and magnetic particles (e.g., Fe-based soft magnetic metal particles) may be used. The exterior body material 85 may be, for example, a material that is granular or particulate at room temperature and becomes fluid (e.g., becomes a highly viscous liquid) when heated (e.g., at 80°C or higher).

[0081] The exterior body material 85 is poured into the exterior body forming pot portion (recess) 77 of the lower mold 75, and then molded. The upper mold 71 and the lower mold 75 are heated to a predetermined mold temperature, the upper mold 71 and the lower mold 75, with the conductor assemblies 10 suspended therefrom, are brought close to each other, and the group of arranged conductor assemblies 10 are inserted into the exterior body forming pot portion (recess) 77, respectively.

[0082] Furthermore, the lower mold 75 is moved toward the upper mold 71, and the exterior body material 85 is filled in each exterior body forming pot portion (recess) 77, thereby forming the exterior body material 85. Thereafter, the upper mold 71 is separated from the lower mold 75, thereby forming the coil device 1 in which the plurality of conductor assemblies 10 are covered with the exterior body portion 50.

[0083] After the coil device 1 is formed, the mounting surface (bottom surface) 1b of the coil device 1 is polished (step S5). The mounting surface (bottom surface) 1b of the coil device 1 is polished to a substantially flush surface by irradiating the mounting surface (bottom surface) 1b with a laser or by scraping the surface with a file. This allows the joinable portions 150, 150 and the joinable portions 250, 250 to be clearly exposed on the mounting surface 1b, and also allows the inter-joinable portion region 1d (see FIG. 1F ) between the joinable portions 150, 150 of the first conductor 11 and the joinable portions 250, 250 of the second conductor 23 to be formed to be substantially flush with the joinable portions 150, 150 and the joinable portions 250, 250.

[0084] The above-mentioned "substantially flush" means that the distance along the Z-axis direction between the inter-joinable portion region 1d, the joinable portion 150 of the first conductor 11, and the joinable portion 250 of the second conductor 23 is at most 50% or less of the thickness WA of the inter-conductor insulating portion 31. The distance along the Z-axis direction between the inter-joinable portion region 1d, the joinable portion 150 of the first conductor 11, and the joinable portion 250 of the second conductor 23 may be within 1 mm, within 5 μm, or within 1 μm.

[0085] The above is an example of the method for manufacturing the coil device 1 according to the present disclosure, but further, electrodes may be appropriately formed on the joinable portions 150, 150 and 250, 250 as needed.

[0086] As described above, in the coil device 1 and the manufacturing method of the coil device 1 according to the present disclosure, the inter-conductor insulation portion 31 filled with an insulating material is formed between the first conductor 11 and the second conductor 23 extending along the inside of the first conductor 11, so that the leakage magnetic flux (leakage inductance) between the first conductor 11 and the second conductor 23 can be controlled in a minute area, thereby improving the coil characteristics. In addition, a coil device capable of handling a large current load can be provided.

[0087] Furthermore, since the inter-conductor insulation portion 31 has a conductor spacing expansion portion (magnetic flux control portion) 35 near the mounting opposing surface (bottom surface) 1b, the leakage magnetic flux (leakage inductance) in the inter-joinable portion region 1d can be further reduced, and the magnetic coupling between the first conductor 11 and the second conductor 23 can be further enhanced.

[0088] Furthermore, by forming an inter-conductor insulation portion 31 between the first conductor 11 and the second conductor 23, it is possible to improve the insulation between the first conductor 11 and the second conductor 23. In other words, it is possible to prevent a short circuit from occurring between the first conductor 11 and the second conductor 23, and it is possible to realize a highly reliable coil device 10. As a result, in this respect as well, it is possible to provide a coil device that is capable of handling a large current and maintaining high characteristics even under a large current load.

[0089] Furthermore, in the present disclosure, the conductor assembly covering portion 30 and the exterior body portion 50 can be formed by compression molding, and manufacturing in this manner allows the conductor assembly covering portion 30 and the exterior body portion 50 to be formed without voids, etc. As a result, magnetic flux can be transmitted efficiently, and the magnetic coupling between the first conductor 11 and the second conductor 23 can be sufficiently increased.

[0090] Furthermore, when the conductor assembly covering portion 30 and the exterior body portion 50 are formed by compression molding, the inter-joinable portion regions 1d on the mounting surface (bottom surface) 1b between the joinable portions 150, 150 of the first conductor 11 and the joinable portions 250, 250 of the second conductor 23 can also be appropriately filled with an insulating material, preventing the formation of voids or the like between the first conductor 11 and the second conductor 23. As a result, defects such as solder creeping up from between the first conductor 11 and the second conductor 23 near the mounting surface (bottom surface) 1b during mounting can be prevented, and from this perspective, high insulation between the first conductor 11 and the second conductor 23 can be ensured.

[0091] Second Embodiment A coil device according to a second embodiment of the present disclosure will be described. In the coil device according to the second embodiment, the magnetic flux control portion 35 at the end of the inter-conductor insulating portion 31 on the mounting surface (bottom surface) 1b side is formed as a different-composition portion having an insulating material composition different from that of the remaining portions. The different-composition portion is an insulating material obtained by adding some material to the insulating material constituting the remaining portions of the inter-conductor insulating portion 31. The added material may be, for example, a magnetic material. The different-composition portion may be formed within a predetermined height range from the mounting surface (bottom surface) 1b. The height may be, for example, 10 μm to 500 μm, or 50 μm to 100 μm.

[0092] By arranging a portion formed of an insulating material having a different composition from other portions between the joinable portion 150 of the first conductor 11 and the joinable portion 250 of the second conductor 21 near the opposing mounting surface (bottom surface) 1b, i.e., by forming a different composition portion, it is possible to further reduce the leakage magnetic flux (leakage inductance) in the region 1d between the joinable portions, similar to, or in addition to, the conductor spacing expansion portion 35 of the first embodiment, and further enhance the magnetic coupling between the first conductor 11 and the second conductor 21.

[0093] By adjusting the insulating material that forms the different-composition portion, or by adjusting the type and amount of material, such as a magnetic material, that is added to form the different-composition portion, it is possible to control within a predetermined range the leakage magnetic flux (leakage inductance) from the inter-joinable portion region 1d, which is the end face exposed on the opposing mounting surface (bottom surface) 1b of the inter-conductor insulating portion 31. The coil device according to the present disclosure may be implemented in such a form.

[0094] Modifications The present disclosure is not limited to the above-described embodiments, and various modifications can be made within the scope of the present disclosure.

[0095] For example, in the above-described embodiment, the conductor assembly covering portion 30 covering the first conductor 11 and the second conductor 23 includes an inter-conductor insulating portion 31 filled between the first conductor 11 and the second conductor 23, an outer insulating portion 32 covering the outer main surface 112 of the first conductor 11, and an inner insulating portion 33 covering the inner main surface 213 of the second conductor 23. However, the coil device according to the present disclosure may be configured without the outer insulating portion 32 or the inner insulating portion 33, and in which the first conductor 11 and the second conductor 23 (i.e., the conductor assembly 10) filled with the inter-conductor insulating portion 31 are directly covered by the joint outer body portion 50. As long as at least the inter-conductor insulating portion 31 is formed, it is possible to control leakage flux (leakage inductance) from the region 1d between the joinable portions.

[0096] For example, in the above-described embodiment, the coil device 1 includes four conductor assemblies 10 , but the coil device 1 may be configured with one conductor assembly 10 .

[0097] In the above-described embodiment, the exterior body 50 is formed by compression molding, but the exterior body 50 may be formed, for example, by an assembled case. In this case, it is preferable that the gap between the outer periphery of the conductor assembly 10 and the inner circumferential surface of the case is as small as possible so as to prevent a gap or the like from being formed between the conductor assembly 10 and the case.

[0098] Furthermore, the coil device according to the present disclosure is configured such that the inside of the second conductor 23 is filled with the central core portion 53 of the outer casing portion 50, as shown in FIG. 3A, but may also have a central core portion (core) 40, as shown in FIG.

[0099] In the first embodiment described above, the ends 140, 140 of the first conductor 11 are not bent near the mounting surface (bottom surface) 1b, and the end faces 141, 141 form the joinable portions 150, 150. The ends 240, 240 of the second conductor 23 are bent inward near the mounting surface (bottom surface) 1b to form inner bent portions 243, 243, and the surfaces exposed to the mounting surface (bottom surface) 1b form the joinable portions 250, 250. In the second embodiment, the ends 140, 140, 240, 240 of both the first conductor 11 and the second conductor 21 are not bent, and the end faces 141, 141, 241, 241 form the joinable portions 150, 150, 250, 250. However, the configuration of the ends (configuration of the joinable portions) of the first conductor and the second conductor is not limited to this.

[0100] 3B , the second conductor 23 may be configured to have inner bent portions 243, 243 bent inward at its end, as in the present embodiment, while the first conductor 12 may have outer bent portions 142, 142 bent outward at its end. In such a configuration, by adjusting the radius of curvature of the bent portion (bent portion) for forming the inner bent portions 243, 243 of the second conductor 23 and the radius of curvature of the bent portion for forming the outer bent portions 142, 142 of the first conductor 12, it is possible to adjust the size of the conductor spacing enlarged portion 35 of the inter-conductor insulating portion 31 (see FIG. 1F ), in other words, the arrangement of the insulating material filled in the inter-joinable portion region 1 d, and to control the leakage flux (leakage inductance) from the inter-joinable portion region 1 d.

[0101] 3C , the second conductor 21 may have no bent portion, and only the first conductor 12 may have outer bent portions 142, 142 formed by bending the ends outward. In such a configuration, by adjusting the radius of curvature of the bent portions for forming the outer bent portions 142, 142 of the first conductor 12, it is possible to adjust the size of the expanded conductor spacing portion 35 of the inter-conductor insulating portion 31 (see FIG. 1F ), in other words, the arrangement of the insulating material filled in the inter-joinable portion region 1 d, and to control the leakage magnetic flux (leakage inductance) from the inter-joinable portion region 1 d.

[0102] Furthermore, although not shown, the second conductor may have an inner bent portion where an end portion is bent inward, and the first conductor may have an inner bent portion where an end portion is bent inward. Alternatively, the first conductor may have no bent portion and the second conductor may have an inner bent portion where an end portion is bent inward, the first conductor may have an inner bent portion and the second conductor may have an inner bent portion where an end portion is bent inward, or both the first conductor and the second conductor may have an outer bent portion.

[0103] This specification discloses the following:

[0104] [1] A coil device comprising: a first conductor extending in a predetermined direction; a second conductor disposed inside the first conductor, at least a portion of which extends along the first conductor; and an inter-conductor insulator located between the first conductor and the second conductor, wherein the inter-conductor insulator has a magnetic flux control unit near a mounting surface that can control leakage inductance within a predetermined range.

[0105] [2] The coil device described in [1], wherein the magnetic flux control unit is a conductor spacing expansion unit in which the spacing between the first conductor and the second conductor at a position close to the mounting opposing surface is wider than the spacing between the first conductor and the second conductor at a position a predetermined distance away from the mounting opposing surface.

[0106] [3] The coil device according to [2], wherein the magnetic flux control section includes an insulating material, and the insulating material has a composition different from that of an insulating material in a region of the inter-conductor insulating section that forms a portion other than the magnetic flux control section.

[0107] [4] The coil device according to any one of [1] to [3], wherein the insulating material included in the magnetic flux control unit includes a magnetic material.

[0108] [5] The coil device according to any one of [1] to [4], wherein the first conductor has a first end and a second end in the extending direction, the first end having a first joinable portion exposed on the mounting opposing surface, and the second end having a second joinable portion exposed on the mounting opposing surface; the second conductor has a third end and a fourth end in the extending direction, the third end having a third joinable portion exposed on the mounting opposing surface, and the fourth end having a fourth joinable portion exposed on the mounting opposing surface; between the first joinable portion of the first conductor and the third joinable portion of the second conductor adjacent to the first joinable portion, the inter-conductor insulation portion is formed so as to be approximately flush with the mounting opposing surface; and between the second joinable portion of the first conductor and the fourth joinable portion of the second conductor adjacent to the second joinable portion, the inter-conductor insulation portion is formed so as to be approximately flush with the mounting opposing surface.

[0109] [6] At least one of the first end and the second end of the first conductor has an outer bent portion bent outward, and the outer surface of the outer bent portion is the first joinable portion or the second joinable portion. [5] A coil device as described in.

[0110] [7] At least one of the third end and the fourth end of the second conductor has an inner bent portion bent inward or an outer bent portion bent outward, and the outer peripheral surface of the inner bent portion or the outer bent portion is the third joinable portion or the fourth joinable portion. [5] A coil device as described in [6] or [7].

[0111] [8] The coil device according to any one of [1] to [7], further comprising an inner insulating portion covering at least the inner surface of the second conductor.

[0112] [9] The coil device according to [8], wherein the inner insulating portion includes a soft magnetic material.

[0113]

[10] The coil device according to any one of [1] to [9], further comprising an outer insulating portion covering at least the outer surface of the first conductor.

[0114]

[11] The coil device according to

[10] , wherein the outer insulating portion includes a soft magnetic material.

[0115]

[12] A coil device according to

[10] or

[11] , further comprising an outer casing that covers the first conductor, the second conductor, the inter-conductor insulation, and the outer insulation and forms the outer surface of the coil device, wherein the outer casing is formed of an insulating material that has a higher magnetic material content than the outer insulation.

[0116]

[13] A method for manufacturing a coil device, comprising: preparing a first conductor and a second conductor, at least a portion of which can extend along the first conductor; arranging the second conductor inside the first conductor such that at least a portion of the second conductor extends along the first conductor; forming an inter-conductor insulation between the first conductor and the second conductor; and the inter-conductor insulation having, in the vicinity of an opposing mounting surface, a magnetic flux control unit capable of controlling leakage inductance within a predetermined range.

[0117]

[14] The method for manufacturing a coil device described in

[13] , wherein the magnetic flux control unit is a conductor spacing expansion unit in which the spacing between the first conductor and the second conductor at a position close to the mounting opposing surface of the coil device is wider than the spacing between the first conductor and the second conductor at a position a predetermined distance away from the mounting opposing surface.

[0118]

[15] The method for manufacturing a coil device according to

[13] or

[14] , wherein the magnetic flux control section includes a first insulating material, and the first insulating material has a composition different from that of an insulating material in a region of the inter-conductor insulating section that forms the portion other than the magnetic flux control section.

[0119]

[16] The method for manufacturing a coil device according to any one of

[13] to

[15] , further comprising a step of forming at least one of an inner insulating portion covering the inner surface of the second conductor or an outer insulating portion covering the outer surface of the first conductor.

[0120]

[17] A method for manufacturing a coil device according to any one of

[13] to

[16] , comprising the steps of placing the first conductor and the second conductor arranged inside the first conductor in a cavity containing a first insulating material, and hardening the first insulating material.

[0121]

[18] A method for manufacturing a coil device according to any one of

[13] to

[17] , further comprising a step of forming an exterior body portion that covers the first conductor and the second conductor on which the inter-conductor insulation portion is formed.

[0122] 1, 3... Coil device 1a... Top surface 1b... Mounting opposing surface (bottom surface) 1c1 to 1c4... Side surface 1d... Region between parts that can be joined 10... Conductor assembly 11 to 13... First conductor 112... Outer main surface 113... Inner main surface 114... Side surface 120... Central region 123... Bent part 130... End side area 140... End part 141... End surface 142... Outer bent part 143... Inner bent part 150... Joinable part 21-23... Second conductor 212... Outer main surface 213... Inner main surface 214... Side surface 220... Central region 223... Bent part 230... End side area 234... Bent part 240... End part 241... End face 242...Outer bending part 243...Inner bending part 250...Joinable part 30...Conductor assembly covering portion 31...Inter-conductor insulating portion 32...Outer insulating portion 33...Inner insulating portion 35...Conductor spacing expansion portion (magnetic flux control portion) 40...Central core portion (core) 50...Exterior body portion 51a...Top surface 51b...Bottom surface 51c1-51c4...Side surfaces 52...Peripheral portion 53...Central core portion 54...Inter-conductor assembly portion 71...Upper mold 72...Central core portion protective member 73...Support body 75...Lower mold 76...Conductor assembly covering pot portion (recess) 77...Exterior body forming pot portion (recess) 83...Conductor assembly covering portion material 85...Exterior body portion material

Claims

1. A coil device comprising: a first conductor extending in a predetermined direction; a second conductor arranged inside the first conductor with at least a portion extending along the first conductor; and an inter-conductor insulator located between the first conductor and the second conductor, wherein the inter-conductor insulator has a magnetic flux control section near the opposing mounting surface that can control leakage inductance within a predetermined range.

2. A coil device as described in claim 1, wherein the magnetic flux control section is a conductor spacing expansion section in which the spacing between the first conductor and the second conductor at a position close to the mounting opposing surface is wider than the spacing between the first conductor and the second conductor at a position a predetermined distance away from the mounting opposing surface.

3. A coil device as described in claim 2, wherein the magnetic flux control section includes an insulating material, and the insulating material has a composition different from that of the insulating material of the region forming the portion other than the magnetic flux control section of the inter-conductor insulation section.

4. The coil device according to claim 3, wherein the insulating material included in the magnetic flux control section includes a magnetic material.

5. The coil device described in claim 1, wherein the first conductor has a first end and a second end in the extending direction, the first end having a first joinable portion exposed on the mounting opposing surface, and the second end having a second joinable portion exposed on the mounting opposing surface; the second conductor has a third end and a fourth end in the extending direction, the third end having a third joinable portion exposed on the mounting opposing surface, and the fourth end having a fourth joinable portion exposed on the mounting opposing surface; between the first joinable portion of the first conductor and the third joinable portion of the second conductor adjacent to the first joinable portion, the inter-conductor insulation portion is formed approximately flush with the mounting opposing surface; and between the second joinable portion of the first conductor and the fourth joinable portion of the second conductor adjacent to the second joinable portion, the inter-conductor insulation portion is formed approximately flush with the mounting opposing surface.

6. A coil device as described in claim 5, wherein at least one of the first end and the second end of the first conductor has an outer bent portion that is bent outward, and the outer surface of the outer bent portion is the first joinable portion or the second joinable portion.

7. A coil device as described in claim 5, wherein at least one of the third end and the fourth end of the second conductor has an inner bent portion bent inward or an outer bent portion bent outward, and the outer peripheral surface of the inner bent portion or the outer bent portion is the third joinable portion or the fourth joinable portion.

8. The coil device of claim 1, further comprising an inner insulation covering at least the inner surface of said second conductor.

9. The coil device of claim 8, wherein the inner insulating portion comprises a soft magnetic material.

10. The coil device of claim 1, further comprising an outer insulation covering at least an outer surface of said first conductor.

11. The coil device of claim 10, wherein the outer insulation comprises a soft magnetic material.

12. A coil device as described in claim 10, further comprising an outer casing portion that covers the first conductor, the second conductor, the inter-conductor insulation portion and the outer insulation portion and forms the outer surface of the coil device, the outer casing portion being formed from an insulating material having a higher magnetic material content than the outer insulation portion.

13. A method for manufacturing a coil device comprising: preparing a first conductor and a second conductor, at least a portion of which can extend along the first conductor; arranging the second conductor inside the first conductor so that at least a portion of the second conductor extends along the first conductor; forming an inter-conductor insulation between the first conductor and the second conductor; and the inter-conductor insulation has, in the vicinity of the opposing mounting surface, a magnetic flux control section capable of controlling leakage inductance within a predetermined range.

14. A method for manufacturing a coil device as described in claim 13, wherein the magnetic flux control section is a conductor spacing expansion section in which the spacing between the first conductor and the second conductor at a position close to the mounting opposing surface of the coil device is wider than the spacing between the first conductor and the second conductor at a position a predetermined distance away from the mounting opposing surface.

15. A method for manufacturing a coil device as described in claim 14, wherein the magnetic flux control includes a first insulating material, and the first insulating material has a composition different from that of the insulating material in the region forming the portion of the inter-conductor insulation other than the magnetic flux control portion.

16. A method for manufacturing a coil device according to claim 13, further comprising the step of forming at least one of an inner insulating portion covering the inner surface of the second conductor and an outer insulating portion covering the outer surface of the first conductor.

17. A method for manufacturing a coil device according to any one of claims 13 to 16, comprising the steps of placing the first conductor and the second conductor arranged inside the first conductor in a cavity containing a first insulating material, and hardening the first insulating material.

18. A method for manufacturing a coil device according to any one of claims 13 to 16, further comprising the step of forming an exterior body portion that covers the first conductor and the second conductor on which the inter-conductor insulation portion is formed.

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