Coil device and manufacturing method of the same

Abstract

To provide a coil device and a manufacturing method of the same, capable of preventing generation of a short circuit fault.SOLUTION: A coil device 1 includes: a core 10 containing a magnetic material, and including a mounting surface 15 and a third surface 13 that is extended in a direction vertical to the mounting surface 15; and a wire 20 that includes a winding part 21 arranged in an inner part of the core 10, and a leading part 22a led from the winding part 21. The leading part 22a includes: a base end part 23 that is extended toward the third surface 13 from the winding part 21; and a flat-shaped terminal part 24 that is continued to the base end pat 23, and is extended along at least the third side surface 13. In the terminal part 24, a plating layer 30 is formed. In a circumference of a boundary part 27 between the base end part 23 and the terminal part 24, a concave part 28 that is concaved toward the side opposite to the mounting surface 15 is formed.SELECTED DRAWING: Figure 4A

Description

Technical Field

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

Background Art

[0002] For example, Patent Document 1 discloses a coil device that can be used as an inductor. The coil device of Patent Document 1 has a winding portion disposed inside a core and a terminal portion drawn from the winding portion and flattened. A part of the terminal portion is disposed inside the core. The remaining part of the terminal portion is exposed from the core and extends along the side surface and the mounting surface of the core.

[0003] In the coil device of Patent Document 1, the terminal portion disposed on the mounting surface can be connected to a mounting substrate by a conductive bonding material (such as solder or a conductive adhesive). That is, since the terminal portion functions as a terminal of the coil device, there is no need to separately provide a terminal for the coil device, and miniaturization of the coil device and reduction of the number of components can be achieved.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in order to enhance the adhesion to the bonding material, a plating layer (such as solder plating) is formed on the terminal portion. However, when the plating layer is formed on the terminal portion, for example, due to the heat of reflow, the plating layer of the terminal portion may melt. In this case, the melted plating layer may spread up to the winding portion through the terminal portion, and there is a risk of short-circuit failure.

[0006] The present disclosure provides a coil device capable of preventing the occurrence of short-circuit defects and a method for manufacturing the same.

Means for Solving the Problems

[0007] The coil device of the present disclosure includes a core containing a magnetic material and having a mounting surface and a side surface extending in a direction perpendicular to the mounting surface, a wire having a winding portion disposed inside the core and a lead portion drawn out from the winding portion, the lead portion having a base end portion extending from the winding portion toward the side surface and a flat terminal portion continuous with the base end portion and extending at least along the side surface, a plating layer is formed on the terminal portion, a recess is formed around the boundary between the base end portion and the terminal portion, recessing toward the side opposite to the mounting surface.

[0008] At least a part of the recess may be exposed from the core.

[0009] The lead portion has an inner surface facing the mounting surface or the side surface and an outer surface facing the inner surface, and the recess may be formed on the inner surface.

[0010] The base end portion has an inclined portion, at least a part of the inclined portion is exposed from the core, and in a cross-section perpendicular to the mounting surface and the side surface, the thickness of the inclined portion may become thinner as it approaches the boundary portion.

[0011] The inclined portion may have an inclined surface that inclines toward the side opposite to the mounting surface as it approaches the boundary portion.

[0012] The lead portion has an inner surface facing the mounting surface or the side surface and an outer surface facing the inner surface, a part of the recess is formed along the inclined surface, and the remaining part of the recess may be formed along the inner surface of the terminal portion.

[0013] The lead-out portion has an inner surface facing the mounting surface or the side surface, and an outer surface facing the inner surface. In the recess, the plating layer may be formed at least on the inner surface.

[0014] In a cross-section perpendicular to the mounting surface and the side surface, the thickness of the lead-out portion may be the thinnest at the recess.

[0015] The terminal portion may have a side portion extending along the side surface and a mounting portion extending along the mounting surface.

[0016] The method for manufacturing the coil device of the present disclosure includes: preparing a wire having a winding portion and a lead-out portion drawn from the winding portion; crushing the lead-out portion to form a flat terminal portion and an inclined portion having a thickness that decreases from the winding portion toward the terminal portion; placing the wire in a cavity of a mold and filling the cavity with a core material including a magnetic material and a resin so that the winding portion is embedded; compressing the core material to form a core; forming a plating layer at least on the terminal portion; bending the terminal portion with respect to the inclined portion toward the core around the periphery of the boundary between the inclined portion and the terminal portion.

Brief Description of the Drawings

[0017]

FIG. 1A

FIG. 1B

FIG. 1C

FIG. 2

FIG. 3

FIG. 4A

FIG. 4B

FIG. 4C

FIG. 4D

FIG. 4E

FIG. 5A

FIG. 5B

FIG. 5C

FIG. 5D

MODE FOR CARRYING OUT THE INVENTION

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the illustrated content is merely schematic and exemplary for understanding the present disclosure, and the appearance and dimensional ratios may be different from the actual object. Further, the present disclosure is not limited to the following embodiments.

[0019] The coil device 1 shown in FIG. 1A is a surface mount type inductor and is mounted, for example, in a power supply circuit of an electronic device. The coil device 1 includes a core 10 and a wire 20 (FIG. 1B). The shape of the core 10 is not particularly limited, but in the example shown in FIG. 1A, it is substantially a hexahedron. The shape of the core 10 may be a cylinder, an elliptical cylinder, an n-sided polyhedron (n≥7), or other polygons. The core 10 has a first side surface 11, a second side surface 12, a third side surface 13, a fourth side surface 14, a mounting surface 15, and a mounting opposing surface 16.

[0020] The ridge line between the second side surface 12 and the third side surface 13 is chamfered, and a chamfered portion 19 is formed on the ridge line between the second side surface 12 and the third side surface 13. By forming the chamfered portion 19 on the core 10, it becomes easier to identify the orientation of the core 10. However, the chamfered portion 19 is not essential and may be omitted.

[0021] The first side surface 11 and the second side surface 12 face each other. The third side surface 13 and the fourth side surface 14 face each other. The mounting surface 15 and the mounting opposing surface 16 face each other.

[0022] In FIG. 1A etc., the X-axis is an axis along the direction in which the first side surface 11 and the second side surface 12 face each other. The Y-axis is an axis along the direction in which the third side surface 13 and the fourth side surface 14 face each other. The Z-axis is an axis along the direction in which the mounting surface 15 and the mounting opposing surface 16 face each other (the direction perpendicular to the mounting surface 15).

[0023] The X-axis, Y-axis, and Z-axis are perpendicular to each other. Hereinafter, for each of the X-axis, Y-axis, and Z-axis, the direction away from the center of the core 10 is referred to as "outer side", and the direction approaching the center of the core 10 is referred to as "inner side". Also, the positive direction side of the Z-axis is referred to as "upper side", and the negative direction side of the Z-axis is referred to as "lower side". However, the upper side in the Z-axis direction does not necessarily coincide with the upper side in the vertical direction. Also, the lower side in the Z-axis direction does not necessarily coincide with the lower side in the vertical direction.

[0024] The width of the core 10 in the X-axis direction is not particularly limited, but is, for example, 3.0 to 10.0 mm. The width of the core 10 in the Y-axis direction is not particularly limited, but is, for example, 3.0 to 10.0 mm. The width of the core 10 in the Z-axis direction (the thickness of the core 10) is not particularly limited, but is 2.0 to 10.0 mm.

[0025] The core 10 is made of a composite material containing a magnetic material and a resin. The method of forming the core 10 is not particularly limited, and examples thereof include powder compacting, injection molding, or machining. In the present embodiment, the core 10 is a compacted body containing a magnetic material and a resin. The magnetic material constituting the core 10 is not particularly limited, and examples thereof include ferrite (Ni-Zn based ferrite, Mn-Zn based ferrite, etc.) or a metal magnetic material. The resin constituting the core 10 is not particularly limited, and examples thereof include an epoxy resin or a phenolic resin.

[0026] The core 10 has first recesses 17a and 17b, and second recesses 18a and 18b. The first recess 17a and the second recess 18a are continuously formed from the third side surface 13 to the mounting surface 15. The first recess 17b and the second recess 18b are continuously formed from the fourth side surface 14 to the mounting surface 15.

[0027] The first recess 17a is formed on the third side surface 13, and the first recess 17b is formed on the fourth side surface 14. A side portion 240 of a lead-out portion 22a described later is disposed in the first recess 17a, and a side portion 240 of a lead-out portion 22b described later is disposed in the first recess 17b. The width of the first recess 17a or 17b in the X-axis direction is wider than the width of the side portion 240 in the X-axis direction.

[0028] The second recesses 18a and 18b are formed on the mounting surface 15. A mounting portion 241 of a lead-out portion 22a described later is disposed in the second recess 18a, and a mounting portion 241 of a lead-out portion 22b described later is disposed in the second recess 18b. The width of the second recess 18a or 18b in the X-axis direction is wider than the width of the mounting portion 241 in the X-axis direction. The depth of the second recess 18a or 18b is equal to or less than the thickness of the mounting portion 241. The first recesses 17a and 17b and the second recesses 18a and 18b are not essential and may be omitted from the core 10.

[0029] As shown in FIG. 1B, the wire 20 has a winding portion 21, a lead-out portion 22a, and a lead-out portion 22b. The wire 20 is, for example, an insulated coated wire in which a conductive core wire is coated with an insulating coating (insulation coating layer). As the wire 20, known windings such as AIW (polyamideimide copper wire), UEW (polyurethane copper wire), and PEW (polyester copper wire) can be adopted. The material constituting the wire is not particularly limited, but is, for example, copper, a copper alloy, silver, or nickel. The wire 20 is a round wire, but may also be a flat wire (for example, a flat wire wound edgewise). The diameter of the wire 20 is not particularly limited, but is, for example, 0.3 to 2.0 mm.

[0030] The winding portion 21 is an air-core coil and is disposed inside the core 10. As shown in FIG. 2, in the winding portion 21, the wire 20 is wound in a spiral shape for 1.5 turns. The winding axis direction of the winding portion 21 corresponds to the Z-axis direction. The number of layers in the winding axis direction (Z-axis direction) of the winding portion 21 is two layers (see FIG. 4A). However, the number of turns of the wire 20 is not particularly limited and may be 1.5 turns or more (for example, 2.5 turns or 3.5 turns). Also, the number of layers in the winding axis direction of the winding portion 21 may be two layers or four layers or more. In the winding portion 21, an insulating coating (insulation coating layer) is formed on the surface of the wire 20. When viewed from a direction (Z-axis direction) perpendicular to the mounting surface 15, the shape of the outer peripheral surface of the winding portion 21 is circular, but may also be elliptical or the like.

[0031] The lead-out portion 22a is led out from the second layer in the winding axis direction of the winding portion 21. The lead-out portion 22b is led out from the first layer in the winding axis direction of the winding portion 21 toward the side opposite to the lead-out portion 22a. The lead-out portions 22a and 22b each have a base end portion 23 and a terminal portion 24. As shown in FIG. 4A, the lead-out portion 22a has an inner surface 25 facing the mounting surface 15 or the third side surface 13 and an outer surface 26 facing the inner surface 25. Also, the lead-out portion 22b has an inner surface 25 facing the mounting surface 15 or the fourth side surface 14 and an outer surface 26 facing the inner surface 25.

[0032] The base end portion 23 and the terminal portion 24 are formed by crushing (pressing or squeezing) the lead-out portion 22a or 22b. The terminal portion 24 is a portion where the lead-out portion 22a or 22b is crushed into a flat shape. On the other hand, the base end portion 23 is a portion where the thickness of the lead-out portion 22a or 22b (the thickness between the inner surface 25 and the outer surface 26) gradually becomes thinner from the winding portion 21 toward the terminal portion 24. In other words, unlike the terminal portion 24, the base end portion 23 is a portion where the lead-out portion 22a or 22b is not completely crushed. Hereinafter, the details of the base end portion 23 and the terminal portion 24 will be described.

[0033] The base end portion 23 extends from the winding portion 21 toward the side surface (the third side surface 13 or the fourth side surface 14) of the core 10. One end in the extending direction of the base end portion 23 is continuous with the winding portion 21, and the other end in the extending direction of the base end portion 23 is continuous with the terminal portion 24.

[0034] The base end portion 23 has an inclined portion 230 and a non-inclined portion 232. At least a part of the inclined portion 230 (in the example shown in FIG. 4A, the whole of the inclined portion 230) is exposed from the side surface (the third side surface 13 or the fourth side surface 14) of the core 10. In a cross section perpendicular to the mounting surface 15 and the third side surface 13 (that is, the YZ cross section), the thickness of the inclined portion 230 (the thickness between the inner surface 25 and the outer surface 26) becomes thinner as it approaches the boundary portion 27 between the base end portion 23 and the terminal portion 24. In the present embodiment, the boundary portion 27 between the base end portion 23 and the terminal portion 24 is exposed from the core 10 and is not disposed inside the core 10.

[0035] As shown in FIG. 3, when viewed from the direction perpendicular to the mounting surface 15 (that is, the Z-axis direction), the width of the inclined portion 230 in the X-axis direction becomes wider as it approaches the boundary portion 27 (FIG. 4A) between the base end portion 23 (the inclined portion 230) and the terminal portion 24.

[0036] As shown in FIG. 4A, an inclined surface 231a is formed on the inner surface 25 of the inclined portion 230. The inclined surface 231a inclines toward the side opposite to the mounting surface 15 (the mounting facing surface 16 side or upward) as it approaches the boundary portion 27 between the base end portion 23 and the terminal portion 24. The inclination angle of the inclined surface 231a with respect to the mounting surface 15 is not particularly limited, but is, for example, 10° or more and less than 90°, or 30° or more and less than 90°.

[0037] An inclined surface 231b is formed on the outer surface 26 of the inclined portion 230. The inclined surface 231b inclines toward the mounting surface 15 side (downward) as it approaches the boundary portion 27 between the base end portion 23 and the terminal portion 24. The inclination angle of the inclined surface 231b with respect to the mounting facing surface 16 is not particularly limited, but is, for example, 10° or more and less than 90°, or 30° or more and less than 90°.

[0038] The non-inclined portion 232 is located between the winding portion 21 and the inclined portion 230. Different from the inclined portion 230, the non-inclined portion 232 is a portion where the lead-out portion 22a or 22b is not crushed. Therefore, the diameter of the wire 20 in the non-inclined portion 232 is equal to the diameter of the wire 20 in the winding portion 21.

[0039] However, the non-inclined portion 232 is not essential. The non-inclined portion 232 may be omitted from the base end portion 23, and the base end portion 23 may be formed of only the inclined portion 230. For example, the base end portion 23 may be inclined so that the thickness of the base end portion 23 (the thickness between the inner surface 25 and the outer surface 26) becomes thinner as it approaches the boundary portion 27 between the base end portion 23 and the terminal portion 24. In this case, one end in the extending direction of the inclined portion 230 is continuous with the winding portion 21, and the other end in the extending direction of the inclined portion 230 is continuous with the terminal portion 24.

[0040] In the inclined portion 230, the coating of the wire 20 is peeled off, and the inclined surfaces 231a and 231b are not covered with the coating. However, the coating may remain on at least one of the inclined surfaces 231a and 231b. On the other hand, in the non-inclined portion 232, the coating of the wire 20 is not peeled off, and the surface of the non-inclined portion 232 is covered with the coating.

[0041] As shown in FIG. 4B, a part of the inclined portion 230 may be disposed inside the core 10, and the remaining part of the inclined portion 230 may be exposed from the side surface (the third side surface 13 or the fourth side surface 14) of the core 10. In the example shown in FIG. 4B, more than 50% of the area of the inclined portion 230 is exposed from the side surface of the core 10, but less than 50% of the area of the inclined portion 230 may be exposed from the side surface of the core 10. Further, as shown in FIG. 4C, the inclined portion 230 may include an inclined surface 231a while not including the inclined surface 231b (FIG. 4A). In the example shown in FIG. 4C, the outer surface 26 of the inclined portion 230 is not inclined and is parallel to the mounting surface 15.

[0042] Also, as shown in FIG. 4D, in a cross section perpendicular to the mounting surface 15 and the third side surface 13 (that is, the YZ cross section), the thickness of the terminal portion 24 (side portion 240) may gradually decrease toward the boundary portion 27 between the base end portion 23 and the terminal portion 24. In the example shown in FIG. 4D, the thickness of the terminal portion 24 is the thinnest at the recess 28.

[0043] As shown in FIG. 4A, the terminal portion 24 is continuous with the base end portion 23 and extends along the side surface (the third side surface 13 or the fourth side surface 14) and the mounting surface 15 of the core 10. The thickness of the terminal portion 24 (the thickness between the inner surface 25 and the outer surface 26) is substantially constant along the extending direction of the terminal portion 24. However, "substantially constant" means that the error in the thickness of the terminal portion 24 is within several percent to several tens of percent (not particularly limited, for example, ±10%, or ±5%, or ±3%). In the terminal portion 24, the coating of the wire 20 is peeled off, and the surface of the terminal portion 24 is not covered with the coating of the wire 20. As shown in FIG. 2, the terminal portion 24 has a flat shape and is formed wider in the X-axis direction than the diameter Φ of the wire 20.

[0044] The width W in the X-axis direction of the terminal portion 24 shown in FIG. 2 is not particularly limited, but is, for example, 1 to 10 mm. The ratio W / Φ of the width W in the X-axis direction of the terminal portion 24 to the diameter Φ of the wire 20 (however, the diameter of the wire 20 in the winding portion 21) is not particularly limited, but is, for example, 1 < W / Φ ≦ 10, or 2 ≦ W / Φ ≦ 8.

[0045] The thickness of the terminal portion 24 is not particularly limited, but is, for example, 0.05 to 0.5 mm. The ratio T / Φ of the thickness T of the terminal portion 24 to the diameter Φ of the wire 20 (however, the diameter of the wire 20 in the winding portion 21) is not particularly limited, but is, for example, 1 / 15 ≦ T / Φ ≦ 1 / 2, or 1 / 10 ≦ T / Φ ≦ 1 / 3.

[0046] As shown in FIG. 4A, the terminal portion 24 has a side portion 240 and a mounting portion 241. The side portion 240 is continuous with the inclined portion 230 and extends along the side surface (the third side surface 13 or the fourth side surface 14) of the core 10. The side portion 240 has a curved portion 242. In the present embodiment, around the boundary portion 27 between the base end portion 23 and the terminal portion 24, the terminal portion 24 is bent with respect to the inclined portion 230 toward the side surface (the third side surface 13 or the fourth side surface 14) of the core 10. Therefore, the curved portion 242 is formed at the bending position of the terminal portion 24.

[0047] The curved portion 242 is located at the upper end portion of the side portion 240 and is curved (bent) so as to protrude in a direction away from the side surface (the third side surface 13 or the fourth side surface 14) of the core 10 or the mounting surface 15. In the curved portion 242, both the inner surface 25 and the outer surface 26 are curved, and the concave portion 28 is formed on the inner surface 25 of the curved portion 242. The curved portion 242 curves from the boundary portion 27 between the base end portion 23 and the terminal portion 24 toward the side surface (the third side surface 13 or the fourth side surface 14) of the core 10. However, as shown in FIG. 4E, the curved portion 242 may be curved only around the boundary portion 27. In the example shown in FIG. 4E, the side portion 240 (the portion excluding the curved portion 242) extends parallel to the side surface of the core 10.

[0048] In addition, in this embodiment, the term "parallel" is not limited to strict parallelism, and a state deviated by several degrees (not particularly limited, for example, 3 degrees) or less from strict parallelism is also included in the concept of "parallel". Also, the term "perpendicular" is not limited to strict perpendicularity, and a state deviated by several degrees (not particularly limited, for example, 3 degrees) or less from strict perpendicularity is also included in the concept of "perpendicular".

[0049] As shown in FIG. 4A, a part of the side portion 240 is in contact with the side surface (the third side surface 13 or the fourth side surface 14) of the core 10. However, as shown in FIG. 4E, the side portion 240 may not be in contact with the side surface of the core 10, and a gap may be formed between the side portion 240 and the side surface of the core 10.

[0050] The mounting portion 241 is continuous with the side portion 240 and extends in a direction perpendicular to the side portion 240. The mounting portion 241 extends along the mounting surface 15. The mounting portion 241 is a portion that is connected to a mounting substrate (not shown) by a conductive bonding material (such as solder or a conductive adhesive).

[0051] As shown in FIG. 1A, the mounting portion 241 of the lead-out portion 22a is disposed in the second recess 18a formed in the mounting surface 15. Also, the mounting portion 241 of the lead-out portion 22b is disposed in the second recess 18b formed in the mounting surface 15. Also, the side portion 240 of the lead-out portion 22a is disposed in the first recess 17a formed in the third side surface 13. Also, the side portion 240 of the lead-out portion 22b is disposed in the first recess 17b formed in the fourth side surface 14.

[0052] As shown in Fig. 4A, plating layers 30 are formed on the inner surface 25 and the outer surface 26 of the lead-out portion 22a. Although detailed illustration is omitted, plating layers 30 are formed on the inner surface 25 and the outer surface 26 of the lead-out portion 22b. In particular, by forming the plating layer 30 on the outer surface 26, the adhesion of a bonding material (e.g., solder or a conductive adhesive) to the outer surface 26 is improved when the coil device 1 is mounted. The plating layer 30 may be a single layer or a multilayer. The plating layer 30 is not particularly limited, but for example, it is Cu plating, Ni plating, Sn plating, Ni-Sn plating, Cu-Ni-Sn plating, Ni-Au plating, Au plating, or Sn-Pb plating (solder plating).

[0053] The plating layer 30 is formed on the portion of the base end portion 23 that is exposed from the core 10, that is, the inclined portion 230. The plating layer 30 is formed on both the inner surface 25 (the inclined surface 231a) and the outer surface 26 (the inclined surface 231b) of the inclined portion 230, but it may be formed on either the inner surface 25 or the outer surface 26. For example, the plating layer 30 may not be formed on the inner surface 25 of the inclined portion 230, and the inner surface 25 of the inclined portion 230 may be covered with the coating of the wire 20.

[0054] Also, the plating layer 30 is formed on either the inner surface 25 or the outer surface 26 of the terminal portion 24. However, the plating layer 30 may not be formed on the inner surface 25 of the terminal portion 24 (the side portion 240 or the mounting portion 241), and it may be formed on the outer surface 26 of the terminal portion 24 (the side portion 240 or the mounting portion 241). In this case, the inner surface 25 of the terminal portion 24 (the side portion 240 or the mounting portion 241) may be covered with the coating of the wire 20.

[0055] The plating layer 30 is formed on both the side portion 240 and the mounting portion 241 of the terminal portion 24. However, the plating layer 30 may not be formed on the side portion 240 and may be formed on the mounting portion 241. In this case, the side portion 240 may be covered with the coating of the wire 20.

[0056] A recess 28 is formed around the boundary portion 27 between the base end portion 23 and the terminal portion 24 (see the enlarged view in FIG. 4A). The recess 28 is formed on the inner surface 25 of the lead-out portion 22a or 22b. Around the boundary portion 27 between the base end portion 23 and the terminal portion 24, the inner surface 25 of the lead-out portion 22a or 22b is curved or bent along the recess 28. The recess 28 is recessed toward the side opposite to the mounting surface 15 (the mounting-opposing surface 16 side or upward). Also, in the example shown in FIG. 4A, the recess 28 is recessed in a direction away from the side surface (the third side surface 13 or the fourth side surface 14) of the core 10 and on the side opposite to the mounting surface 15.

[0057] The recess 28 is formed by the inclined surface 231a of the base end portion 23 (the inclined portion 230) and the inner surface 25 of the terminal portion 24 (the side portion 240). That is, a part of the recess 28 is formed along the inclined surface 231a, and the remaining part of the recess 28 is formed along the inner surface 25 of the terminal portion 24 (the side portion 240). In particular, around the boundary portion 27 between the base end portion 23 and the terminal portion 24, the recess 28 is formed along the inclined surface 231a and the inner surface 25 (i.e., the curved surface of the curved portion 242) of the curved portion 242. The bottom of the recess 28 is formed around the boundary portion 27 between the base end portion 23 and the terminal portion 24.

[0058] At least a part (in this embodiment, all) of the recess 28 is exposed from the core 10. However, a part of the recess 28 may be exposed from the core 10 and the remaining part of the recess 28 may be disposed inside the core 10. For example, as shown in FIG. 4B, when a part of the inclined portion 230 is disposed inside the core 10, a part of the recess 28 is exposed from the core 10 and the remaining part of the recess 28 is disposed inside the core 10. As shown in FIG. 4A, the bottom of the recess 28 is located at a position spaced outward in the Y-axis direction from the side surface (the third side surface 13 or the fourth side surface 14) of the core 10.

[0059] A plating layer 30 is formed on the recess 28. That is, in the recess 28, the plating layer 30 is formed on the inner surface 25 (the inclined surface 231a) of the inclined portion 230. Also, in the recess 28, the plating layer 30 is formed on the inner surface 25 of the terminal portion 24 (the terminal portion 24). However, the plating layer 30 may not be formed on the recess 28. In this case, in the recess 28, the inclined surface 231a and the inner surface 25 of the terminal portion 24 may be covered by the coating of the wire 20.

[0060] A space 29 is formed inside the recess 28. The space 29 is surrounded by the inclined surface 231a, the inner surface 25 of the terminal portion 24 (the side portion 240), and the side surface (the third side surface 13 or the fourth side surface 14) of the core 10. In a cross-section perpendicular to the mounting surface 15 and the third side surface 13 (that is, the YZ cross-section), the space 29 extends from the bottom of the recess 28 toward the side surface (the third side surface 13 or the fourth side surface 14) of the core 10. However, as shown in FIG. 4E, the space 29 may extend along the side surface (the third side surface 13 or the fourth side surface 14) of the core 10 toward the mounting surface 15.

[0061] Next, with reference to FIGS. 5A to 5D, etc., the manufacturing method of the coil device 1 shown in FIG. 1B will be described. First, as shown in FIG. 5A, a wire 20 having a winding portion 21 and lead portions 22a and 22b drawn from the winding portion 21 is prepared. The wire 20 is a round wire, but may also be a flat wire. The winding portion 21 is an air-core coil, and the lead portions 22a and 22b are drawn from the winding portion 21 toward opposite sides.

[0062] Next, as shown in FIG. 5B, the lead-out portion 22a is crushed to form a flat terminal portion 24 and an inclined inclined portion 230 (see FIG. 4A) on the lead-out portion 22a. The inclined portion 230 has a thickness (the thickness between the inner surface 25 and the outer surface 26) that gradually becomes thinner as it goes from the winding portion 21 toward the terminal portion 24. The range in which the lead-out portion 22a is crushed is, for example, the range from the boundary portion 22a1 between the winding portion 21 and the lead-out portion 22a to the tip portion 22a2 of the lead-out portion 22a. As a result, a base end portion 23 having the inclined portion 230 shown in FIG. 4A is formed around the boundary portion 22a1 between the winding portion 21 and the lead-out portion 22a. Also, a terminal portion 24 is formed on the tip side of the lead-out portion 22a with respect to the base end portion 23.

[0063] Also, as shown in FIG. 5B, the lead-out portion 22b is crushed to form a flat terminal portion 24 and an inclined inclined portion 230 (see FIG. 4A) on the lead-out portion 22b. The inclined portion 230 has a thickness that gradually becomes thinner as it goes from the winding portion 21 toward the terminal portion 24. The range in which the lead-out portion 22b is crushed is, for example, the range from the boundary portion 22b1 between the winding portion 21 and the lead-out portion 22b to the tip portion 22b2 of the lead-out portion 22b. As a result, a base end portion 23 having the inclined portion 230 shown in FIG. 4A is formed around the boundary portion 22b1 between the winding portion 21 and the lead-out portion 22b. Also, a terminal portion 24 is formed on the tip side of the lead-out portion 22b with respect to the base end portion 23.

[0064] Next, the wire 20 is placed in the cavity of a mold (not shown), and a core material containing a magnetic material and resin is filled into the cavity. At this time, the winding portion 21 is embedded in the core material, and at least a part of the base end portion 23 is exposed from the core material, and the terminal portion 24 is exposed from the core material, and the core material is filled into the cavity. Next, the core material filled in the cavity is compressed and cured at a predetermined mold temperature for a predetermined time to form the core 10 shown in FIG. 5C.

[0065] Next, for example, the terminal portion 24 exposed from the core 10 is irradiated with a laser to peel off the coating on the surface of the terminal portion 24. Also, for example, the base end portion 23 (inclined portion 230) exposed from the core 10 is irradiated with a laser to peel off the coating on the surface of the base end portion 23.

[0066] Next, as shown in FIG. 5D, a plating layer 30 is formed on the terminal portion 24 exposed from the core 10. In the present embodiment, the plating layer 30 is formed on the inner surface 25 (FIG. 4A) and the outer surface 26 (FIG. 4A) of the terminal portion 24, but the plating layer 30 may be formed only on the outer surface 26 of the terminal portion 24. Further, the plating layer 30 is formed on the inner surface 25 (inclined surface 231a) and the outer surface 26 (inclined surface 231b) of the base end portion 23 (inclined portion 230) exposed from the core 10. In the present embodiment, the plating layer 30 is formed on the inner surface 25 and the outer surface 26 of the base end portion 23, but the plating layer 30 may be formed only on the outer surface 26 of the base end portion 23. The plating layer 30 is not particularly limited, but is, for example, Sn-Pb plating (solder plating). The method of forming the plating layer 30 is not particularly limited, but is, for example, electroless plating, electrolytic plating, or dipping. Note that the step of forming the plating layer 30 on the terminal portion 24 and / or the base end portion 23 may be performed before the core 10 is molded (before the step shown in FIG. 5C).

[0067] Next, as shown in FIG. 4A, around the boundary portion 27 between the base end portion 23 (inclined portion 230) and the terminal portion 24, the terminal portion 24 of the lead-out portion 22a is bent with respect to the base end portion 23 (inclined portion 230) toward the third side surface 13 of the core 10 (see the figure shown by the two-dot chain line in FIG. 4A). Thereby, the side portion 240 of the terminal portion 24 is disposed along the third side surface 13. Further, around the boundary portion 27 between the base end portion 23 (inclined portion 230) and the terminal portion 24, the terminal portion 24 of the lead-out portion 22b is bent with respect to the base end portion 23 (inclined portion 230) toward the fourth side surface 14 of the core 10. Thereby, the side portion 240 of the terminal portion 24 is disposed along the fourth side surface 14.

[0068] Next, the tip portion of the terminal portion 24 disposed along the third side surface 13 is bent toward the mounting surface 15 of the core 10. Thereby, the mounting portion 241 of the terminal portion 24 is disposed along the mounting surface 15. Further, the tip portion of the terminal portion 24 disposed along the fourth side surface 14 is bent toward the mounting surface 15 of the core 10. Thereby, the mounting portion 241 of the terminal portion 24 is disposed along the mounting surface 15. As described above, the coil device 1 can be manufactured.

[0069] When manufacturing the coil device 1, for example, due to the heat of reflow, the plating layer 30 of the terminal portion 24 may melt. In the coil device 1 of the present embodiment, as shown in FIG. 4A, a recess 28 that is recessed toward the side opposite to the mounting surface 15 is formed around the boundary portion 27 between the base end portion 23 and the terminal portion 24. Therefore, the melted plating layer 30 (hereinafter referred to as "melted plating") is likely to accumulate in the recess 28, and it is difficult for the melted plating to spread to the winding portion 21 through the terminal portion 24 and the base end portion 23. Further, due to the formation of the recess 28 in the lead-out portion 22a, the creepage distance from the terminal portion 24 to the winding portion 21 becomes longer, and it is difficult for the melted plating to spread to the winding portion 21 through the terminal portion 24 and the base end portion 23. As a result, it is difficult for the melted plating to adhere to the winding portion 21, and the occurrence of a short-circuit defect can be prevented.

[0070] Also, when mounting the coil device 1, when connecting the terminal portion 24 to a mounting substrate (not shown) with a bonding material (such as solder or a conductive adhesive), the bonding material may spread through the terminal portion 24. Even in such a case, the bonding material is likely to accumulate in the recess 28, so it is difficult for the bonding material to spread to the winding portion 21 through the terminal portion 24 and the base end portion 23. Further, due to the formation of the recess 28 in the lead-out portion 22a, the creepage distance from the terminal portion 24 to the winding portion 21 becomes longer, so it is difficult for the bonding material to spread to the winding portion 21 through the terminal portion 24 and the base end portion 23. As a result, it is difficult for the bonding material to adhere to the winding portion 21, and in this regard as well, the occurrence of a short-circuit defect can be prevented.

[0071] Also, at least a part (in this embodiment, all) of the recess 28 is exposed from the core 10. Therefore, when mounting the coil device 1, the melted plating or the bonding material is likely to accumulate in the recess 28 outside the core 10 and is difficult to enter the inside of the core 10. As a result, it is possible to effectively prevent the melted plating or the bonding material from spreading to the winding portion 21.

[0072] Further, the lead-out portion 22a has an inner surface 25 facing the mounting surface 15 or the third side surface 13, and an outer surface 26 facing the inner surface 25. And the recess 28 is formed in the inner surface 25. Therefore, the recess 28 curves (bends) toward the side opposite to the mounting surface 15. Thereby, it becomes easier for the molten plating or the bonding material to accumulate in the recess 28, and it is possible to effectively prevent the molten plating or the bonding material from rising up to the winding portion 21.

[0073] Also, the base end portion 23 has an inclined portion 230, and at least a part (in this embodiment, all) of the inclined portion 230 is exposed from the core 10. And in a cross section perpendicular to the mounting surface 15 and the third side surface 13 (that is, the YZ cross section), the thickness of the inclined portion 230 becomes thinner as it approaches the boundary portion 27. Therefore, during the manufacture of the coil device 1, it becomes easier to bend the terminal portion 24 with respect to the inclined portion 230 around the boundary portion 27 between the inclined portion 230 and the terminal portion 24. Thereby, it is possible to easily form a recess 28 that is recessed toward the side opposite to the mounting surface 15 around the boundary portion 27 between the inclined portion 230 and the terminal portion 24.

[0074] Further, the inclined portion 230 has an inclined surface 231a that inclines toward the side opposite to the mounting surface 15 as it approaches the boundary portion 27. Therefore, during the manufacture of the coil device 1, when the terminal portion 24 is bent with respect to the inclined portion 230 around the boundary portion 27 between the inclined portion 230 and the terminal portion 24, a recess 28 is formed along the inclined surface 231a. Thereby, it is possible to easily form a recess 28 that is recessed toward the side opposite to the mounting surface 15 around the boundary portion 27 between the inclined portion 230 and the terminal portion 24. Also, a recess 28 having a depth corresponding to the inclination angle of the inclined surface 231a can be formed. Therefore, the storage amount of the molten plating or the bonding material in the recess 28 can be adjusted according to the depth of the recess 28.

[0075] Further, a part of the recess 28 is formed along the inclined surface 231a, and the remaining part of the recess 28 is formed along the inner surface 25 of the terminal portion 24. Therefore, the recess 28 that is recessed toward the side opposite to the mounting surface 15 can be formed so that the bottom of the recess 28 is located around the boundary portion 27 between the inclined portion 230 and the terminal portion 24. Thereby, the molten plating or the bonding material is likely to accumulate in the recess 28, and the wicking of the molten plating or the bonding material to the winding portion 21 can be effectively prevented.

[0076] Also, in the recess 28, a plating layer 30 is formed at least on the inner surface 25. Therefore, the molten plating or the bonding material flowing into the recess 28 is likely to stay in the recess 28 and is less likely to flow out of the recess 28 toward the winding portion 21. Thereby, the wicking of the molten plating or the bonding material to the winding portion 21 can be effectively prevented.

[0077] Also, as shown in FIG. 4D, in a cross section perpendicular to the mounting surface 15 and the third side surface 13 (i.e., the YZ cross section), the thickness of the lead-out portion 22a or 22b is the thinnest at the recess 28. Therefore, a deeper recess 28 can be formed toward the side opposite to the mounting surface 15, and the molten plating or the bonding material can be easily accumulated in the recess 28.

[0078] Also, as shown in FIG. 4A, the terminal portion 24 has a side portion 240 extending along the third side surface 13 and a mounting portion 241 extending along the mounting surface 15. Therefore, the mounting portion 241 can be connected to the mounting substrate by the bonding material. Also, a fillet of the bonding material can be formed on the side portion 240, and the mounting strength of the coil device 1 is improved.

[0079] Further, in the manufacturing method of the coil device 1 of the present embodiment, the terminal portion 24 is bent with respect to the inclined portion 230 toward the core 10 around the boundary portion 27 between the inclined portion 230 and the terminal portion 24. Therefore, a recessed portion 28 that is recessed toward the side opposite to the mounting surface 15 can be formed along the inclined portion 230 and the terminal portion 24 around the boundary portion 27 between the inclined portion 230 and the terminal portion 24. As a result, when the coil device 1 is mounted, the molten plating or the bonding material easily accumulates in the recessed portion 28, and it is possible to prevent the molten plating or the bonding material from rising onto the winding portion 21.

[0080] The present disclosure is not limited to the above-described embodiments, and various modifications can be made within the scope of the present disclosure.

[0081] In the above embodiment, the application example of the present disclosure to the inductor has been described, but the present disclosure may be applied to other coil devices.

[0082] The inclined portion 230 shown in FIGS. 4C to 4E has one inclined surface 231a, but may have two inclined surfaces 231a and 231b (see FIG. 4A). Further, although the inclined portion 230 shown in FIGS. 4C to 4E is entirely exposed from the core 10, it may be partially exposed from the core 10 (see FIG. 4B). That is, a part of the inclined portion 230 shown in FIGS. 4C to 4E may be disposed inside the core 10.

Explanation of reference numerals

[0083] 1... Coil device 10... Core 11... First side surface 12... Second side surface 13... Third side surface 14... Fourth side surface 15... Mounting surface 16... Mounting opposite surface 17a, 17b... First recess 18a, 18b... Second recess 19... Chamfered portion 20... Wire 21... Winding portion 22a, 22b... Lead-out portion 23…Base end portion 230…Inclined portion 231a, 231b…Inclined surface 232…Non-inclined portion 24…Terminal portion 240…Side portion 241…Mounting portion 242…Bending portion 25…Inner surface 26…Outer surface 27…Boundary portion 28…Concave portion 29…Space 30…Plating layer

Claims

1. A core including a magnetic material, having a mounting surface and a side surface extending in a direction perpendicular to the mounting surface; A wire having a winding portion disposed inside the core and a lead portion drawn out from the winding portion; The lead portion has a base end portion extending from the winding portion toward the side surface and a flat terminal portion continuous with the base end portion and extending at least along the side surface; A plating layer is formed on the terminal portion; A coil device in which a recess recessed toward the side opposite to the mounting surface is formed around a boundary portion between the base end portion and the terminal portion.

2. The coil device according to claim 1, wherein at least a part of the recess is exposed from the core.

3. The lead portion has an inner surface facing the mounting surface or the side surface and an outer surface facing the inner surface; The coil device according to claim 1 or 2, wherein the recess is formed on the inner surface.

4. The base end portion has an inclined portion; At least a part of the inclined portion is exposed from the core; The coil device according to claim 1 or 2, wherein in a cross section perpendicular to the mounting surface and the side surface, the thickness of the inclined portion becomes thinner as it approaches the boundary portion.

5. The coil device according to claim 4, wherein the inclined portion has an inclined surface inclined toward the side opposite to the mounting surface as it approaches the boundary portion.

6. The lead portion has an inner surface facing the mounting surface or the side surface and an outer surface facing the inner surface; A part of the recess is formed along the inclined surface; The coil device according to claim 5, wherein the remaining part of the recess is formed along the inner surface of the terminal portion.

7. The lead portion has an inner surface facing the mounting surface or the side surface and an outer surface facing the inner surface; The coil device according to claim 1 or 2, wherein in the recess, the plating layer is formed at least on the inner surface.

8. The coil device according to claim 1 or 2, wherein in a cross section perpendicular to the mounting surface and the side surface, the thickness of the lead portion is thinnest at the recess.

9. The coil device according to claim 1 or 2, wherein the terminal portion has a side portion extending along the side surface and a mounting portion extending along the mounting surface.

10. A step of preparing a wire having a winding portion and a lead portion drawn out from the winding portion; A step of crushing the lead-out portion to form a flat terminal portion and an inclined portion having a thickness that becomes thinner as it goes from the winding portion toward the terminal portion; A step of placing the wire in a cavity of a mold and filling the cavity with a core material containing a magnetic material and resin so that the winding portion is embedded; A step of compressing the core material to form a core; A step of forming a plating layer at least on the terminal portion; A method for manufacturing a coil device, comprising a step of bending the terminal portion with respect to the inclined portion toward the core around a periphery of a boundary between the inclined portion and the terminal portion.

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