Coil device

Abstract

To provide a coil device in which short-circuiting failure between an electrode and a coil, and also between a conductive member adhered to the electrode and the coil can be prevented.SOLUTION: A coil device 10 has: a core which has a winding core part 23 arranged substantially perpendicular to a mounting surface and a flange part 22 formed on one axial end of the winding core part 23; a coil 30 disposed around the winding core part 23; and an electrode 40 to which a lead-out part 30a of the coil 30 is connected, and at least part of which is formed on an outer circumferential surface of the flange part 22. The electrode 40 has a recess 420 which is recessed toward an outer end surface 221 side of the flange part 22.SELECTED DRAWING: Figure 2

Description

Technical Field

[0005] ,

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

Background Art

[0002] Conventionally, a coil device including a so-called vertical drum core in which a bobbin portion is arranged substantially perpendicular to a mounting surface has been known. In this type of coil device, for example, as described in Patent Document 1, electrodes may be formed so as to straddle the outer end surface and the outer peripheral surface of a flange portion. Here, a part of the electrode formed on the outer end surface of the flange portion functions as a mounting surface with a mounting substrate, and a part of the electrode formed on the outer peripheral surface of the flange portion functions as a formation surface for a solder fillet. When mounting the coil device on a mounting substrate, by forming a solder fillet on a part of the electrode formed on the outer peripheral surface of the flange portion, it has been possible to mount the coil device on the mounting substrate with sufficient mounting strength. <000***0>

[0003] However, in the invention described in Patent Document 1, when a part of the outer peripheral surface of the flange portion is arranged close to the outer peripheral surface of the coil, the outer peripheral surface of the coil may contact the electrode, and there is a risk of a short circuit occurring between them. Further, when a solder fillet is formed on a part of the electrode formed on the outer peripheral surface of the flange portion, a part of the solder fillet may ride up (wrap around) on the inner end surface of the flange portion, and the solder fillet may contact the outer peripheral surface of the coil, and there is a risk of a short circuit occurring between them. Therefore, a technique for solving the above problems is required.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] To achieve the above objective, the coil device according to the present invention is A core having a winding core portion arranged substantially perpendicular to the mounting surface and a flange portion formed at one end of the winding core portion in the axial direction, The coil arranged in the aforementioned winding core, The lead portion of the coil is connected to an electrode, which at least a part of which is formed on the outer surface of the flange portion, The electrode has a recess that is recessed toward the outer end surface of the flange.

[0007] In the coil device according to the present invention, the electrode has a recess that is indented toward the outer end surface of the flange. Therefore, at the location of the recess, the electrode is formed at a distance corresponding to the degree of the recess from the outer surface of the coil. This reduces the risk of contact between the outer surface of the coil and the electrode, and prevents short-circuit failures from occurring between the coil and the electrode.

[0008] Furthermore, in the recessed area, the electrode is formed at a distance corresponding to the degree of the recess from the inner end surface of the flange. Therefore, when a conductive material (such as solder fillet) adheres to the electrode, it becomes less likely for a portion of the solder fillet to ride up (wrap around) to the inner end surface of the flange. This reduces the risk of contact between the outer surface of the coil and the solder fillet, preventing short-circuit failures between the coil and the solder fillet.

[0009] Furthermore, when forming electrodes on the outer surface of the flange, by forming the electrode material on the outer surface of the flange in such a way that a recess is formed, it is possible to prevent the electrode material from unintentionally riding up onto the inner end surface of the flange.

[0010] Preferably, at the location of the recess, an electrode-free region is provided between the electrode and the intersection of the inner end surface of the flange and the outer surface, and the electrode is not formed in the electrode-free region. With this configuration, at the location of the recess, an electrode-free region is interposed between the outer surface of the coil and the electrode, so it is possible to increase the distance between the electrode and the outer surface of the coil by an amount corresponding to the size of the electrode-free region. Therefore, the risk of the outer surface of the coil coming into contact with the electrode can be effectively reduced.

[0011] Furthermore, at the location of the recess, a non-electrode-formed region is interposed between the inner end surface of the flange and the electrode. This allows the distance between the electrode and the inner end surface of the flange to be increased by an amount corresponding to the size of the non-electrode-formed region. Therefore, it becomes less likely for a portion of the solder fillet formed on the electrode to ride up onto the inner end surface of the flange, effectively reducing the risk of the outer surface of the coil coming into contact with the solder fillet.

[0012] Preferably, the electrode extends along the outer circumference of the flange, and the recess is formed in the central part of the electrode in the direction of extension. With this configuration, it is possible to form a recess over a wide area along the direction of extension of the electrode, centered on the central part of the electrode in the direction of extension. Therefore, the risk of the outer surface of the coil coming into contact with the electrode or solder fillet can be effectively reduced.

[0013] Furthermore, typically, the electrode and the outer surface of the coil are positioned closest together, especially in the central part of the electrode's extending direction. Therefore, by forming a recess in the central part of the electrode's extending direction, the risk of the outer surface of the coil coming into contact with the electrode or solder fillet can be effectively reduced.

[0014] Preferably, the electrode extends along the outer circumference of the flange, and the thickness of the electrode decreases towards the center in the direction of electrode extension. By reducing the thickness of the electrode, the protrusion of the electrode from the outer surface of the flange is suppressed, and the risk of the outer surface of the coil coming into contact with the electrode or solder fillet can be reduced. In particular, by reducing the thickness of the electrode towards the center in the direction of electrode extension, it is possible to form a wide area of ​​low electrode thickness along the direction of electrode extension, centered on the center in the direction of electrode extension. This effectively reduces the risk of the outer surface of the coil coming into contact with the electrode or solder fillet.

[0015] Preferably, the thickness of the electrode decreases towards the inner end face of the flange. With this configuration, the protrusion of the electrode from the outer surface of the flange is suppressed closer to the inner end face of the flange, i.e., closer to the coil, effectively reducing the risk of the outer surface of the coil coming into contact with the electrode. Also, the protrusion of the solder fillet formed on the electrode is suppressed closer to the coil, effectively reducing the risk of the outer surface of the coil coming into contact with the solder fillet. In addition, a portion of the solder fillet formed on the electrode is less likely to ride up onto the inner end face of the flange, and in this respect as well, the risk of the outer surface of the coil coming into contact with the solder fillet can be effectively reduced.

[0016] Preferably, the electrode has a connecting portion to which the lead portion of the coil is connected, and the connecting portion is provided at a position different from the position of the recess. At such a position, it is possible to secure a sufficient electrode width for the connecting portion along the axial direction of the winding core, compared to the position of the recess. Therefore, by providing the connecting portion at a position different from the position of the recess, the lead portion of the coil can be reliably connected to the connecting portion.

[0017] Preferably, when viewed from the axial direction of the winding core, the flange has a polygonal shape, the outer circumferential surface of the flange has multiple adjacent surfaces, the electrode spans multiple of these surfaces, and the connecting portion is formed on a surface different from the surface where the recess is formed. With this configuration, on the surface where the connecting portion is formed, sufficient electrode width of the connecting portion can be secured along the axial direction of the winding core, and the lead portion of the coil can be reliably connected to the connecting portion. On the surface where the recess is formed, sufficient distance can be secured between the outer circumferential surface of the coil and the electrode, effectively reducing the risk of the outer circumferential surface of the coil contacting the electrode. Furthermore, sufficient distance can be secured between the inner end surface of the flange and the electrode along the axial direction of the winding core, effectively preventing a portion of the solder fillet formed on the electrode from riding up onto the inner end surface of the flange.

[0018] Preferably, the thickness of the electrode is smaller at the recessed portion compared to the joint portion. With this configuration, the thickness of the electrode is relatively smaller at the recessed portion and relatively larger at the joint portion. As a result, it is possible to achieve all of the above-mentioned effects, namely, a reduction in the risk of contact between the outer surface of the coil and the electrode, a reduction in the risk of contact between the outer surface of the coil and the solder fillet (prevention of solder fillet riding up onto the inner end surface of the flange), and an improvement in the reliability of the connection of the coil lead portion to the joint portion.

[0019] Preferably, the electrode contains metal and glass. With this configuration, the electrode can be formed on the outer surface of the flange with sufficient connection strength. [Brief explanation of the drawing]

[0020] [Figure 1] Figure 1 is a perspective view of a coil device according to one embodiment of the present invention. [Figure 2] Figure 2 is a perspective view of the coil device shown in Figure 1 with the outer resin casing omitted. [Figure 3A] Figure 3A is a side view of the coil device shown in Figure 1, viewed from direction IIIA. [Figure 3B] Figure 3B is a side view of the coil device shown in FIG. 1 as viewed from the IIIB direction. [Figure 4] Figure 4 is a bottom view of the coil device shown in FIG. 1. [Figure 5A] Figure 5A is a cross-sectional view of the coil device shown in FIG. 1 taken along the VA-VA line. [Figure 5B] Figure 5B is a cross-sectional view of the coil device shown in FIG. 1 taken along the VB-VB line. [Figure 6A] Figure 6A is a partially enlarged cross-sectional view of the coil device shown in FIG. 3A taken along the VIA-VIA line. [Figure 6B] Figure 6B is a partially enlarged cross-sectional view of the coil device shown in FIG. 3A taken along the VIB-VIB line.

MODE FOR CARRYING OUT THE INVENTION

[0021] Hereinafter, the present invention will be described based on the embodiments shown in the drawings.

[0022] As shown in FIG. 1, a coil device 10 according to an embodiment of the present invention is mounted on in-vehicle equipment or the like and functions as, for example, an inductor. The coil device 10 includes a core 20, a coil 30 (FIG. 2), a first electrode 40, and a second electrode 50. In addition to these, the coil device 10 may further include an exterior resin 60.

[0023] In FIG. 1, the X-axis corresponds to the extending direction of each long side of the first electrode 40 and the second electrode 50. The Y-axis corresponds to the direction in which the first electrode 40 and the second electrode 50 face each other. The Z-axis is an axis extending perpendicular to the mounting surface of the coil device 10 and corresponds to the axial direction of the bobbin portion 23 (FIG. 3A) of the core 20.

[0024] As shown in Figure 2, the core 20 has a first flange portion 21, a second flange portion 22, and a winding core portion 23 (Figure 3A). The core 20 is a so-called vertical drum core in which the winding core portion 23 is arranged substantially perpendicular to the mounting surface. The size of the core 20 is not particularly limited, but its width in the X-axis direction is 1.0 to 6.0 mm, its width in the Y-axis direction is 1.0 to 6.0 mm, and its width in the Z-axis direction is 0.5 to 3.0 mm.

[0025] The core 20 is formed from a material containing a magnetic material and a resin. Examples of the magnetic material forming the core 20 include ferrite particles or metallic magnetic particles. Examples of ferrite particles include Ni-Zn ferrite and Mn-Zn ferrite. Examples of metallic magnetic particles are not particularly limited, but include Fe-Ni alloy powder, Fe-Si alloy powder, Fe-Si-Cr alloy powder, Fe-Co alloy powder, Fe-Si-Al alloy powder, amorphous iron, etc. Examples of the resin forming the core 20 are not particularly limited, but include epoxy resin, phenolic resin, polyester resin, polyurethane resin, polyimide resin, other synthetic resins, or other non-magnetic materials. The core 20 may also be a sintered body of a metallic magnetic material.

[0026] The core portion 23 (see Figures 3A and 5A) has a columnar shape and a substantially circular cross-sectional shape. The cross-sectional shape of the core portion 23 is not particularly limited and may be rectangular, substantially octagonal, or other polygonal. The core portion 23 is positioned substantially perpendicular to the mounting surface. The coil 30 is attached to the outer circumferential surface of the core portion 23. The outer circumferential surface of the coil 30 is positioned near the outer edge of the second flange portion 22. As the wire forming the coil 30, for example, a core material made of a good conductor such as copper can be used, covered with an insulating material such as imide-modified polyurethane, and the outermost surface can be covered with a thin resin film such as polyester.

[0027] The first flange portion 21 is formed at one axial end (upper end) of the winding core portion 23, and the second flange portion 22 is formed at the other axial end (lower end) of the winding core portion 23. The thickness of the first flange portion 21 and the second flange portion 22 is not particularly limited, but is preferably 300 to 600 μm. The first flange portion 21 and the second flange portion 22 have the same shape and, when viewed from the Z-axis direction, are approximately octagonal. However, the shape of the first flange portion 21 and the second flange portion 22 when viewed from the Z-axis direction is not limited to this, and may be circular, elliptical, quadrilateral (rectangle), hexagonal, or other polygons when viewed from the Z-axis direction.

[0028] When mounting the coil device 10 onto a mounting substrate (not shown), the bottom surface of the second flange portion 22 is positioned to face the mounting substrate. An identifier such as a barcode may be attached to the top surface of the first flange portion 21.

[0029] The first electrode 40 and the second electrode 50 have mutually symmetrical shapes. The first electrode 40 and the second electrode 50 are made of a conductive material, such as a metal paste baked film or a metal plating film. One lead portion 30a of the coil 30 is connected to the first electrode 40, for example by thermocompression bonding. The other lead portion 30b of the coil 30 is connected to the second electrode 50, for example by thermocompression bonding.

[0030] The first electrode 40 is formed on one side in the Y-axis direction, straddling the outer circumferential surface (circumferential side surface) 220 and the outer end surface (mounting surface) 221 of the second flange portion 22. On the outer circumferential surface 220, the first electrode 40 straddles three adjacent surfaces (first surface 220a, second surface 220b, and third surface 220c) that are connected to each other. On one side in the Y-axis direction, the first electrode 40 extends along the outer circumferential direction of the second flange portion 22 in a substantially C-shape (or arc shape).

[0031] The second electrode 50 is formed on the other side in the Y-axis direction, straddling the outer peripheral surface (circumferential surface) 220 and the outer end surface 221 of the second flange portion 22. On the outer peripheral surface 220, the second electrode 50 straddles three adjacent surfaces (the fourth surface 220d, the fifth surface 220e, and the sixth surface 220f shown in Figure 5A) that are connected to each other. On the other side in the Y-axis direction, the second electrode 50 extends along the outer peripheral direction of the second flange portion 22 in a substantially C-shape (or arc shape).

[0032] The first electrode 40 and the second electrode 50 are formed by applying, for example, Ag paste to the outer peripheral surface 220 and the outer end surface 221 of the second flange portion 22, baking it, and then applying, for example, electroplating or electroplating to the surface to form a plating film. The material of the metal paste is not particularly limited, and examples include Cu paste and Ag paste. The plating film may be single-layer or multi-layer, and examples include Cu plating, Ni plating, Sn plating, Ni-Sn plating, Cu-Ni-Sn plating, Ni-Au plating, and Au plating. The thickness of the first electrode 40 and the second electrode 50 is not particularly limited, but is preferably 0.1 to 30 μm.

[0033] Furthermore, the first electrode 40 and the second electrode 50 may contain glass in addition to the metals mentioned above. In this case, the first electrode 40 and the second electrode 50 can be formed on the outer circumferential surface 220 of the second flange portion 22 with sufficient connection strength. Alternatively, the first electrode 40 and the second electrode 50 may be formed from a conductive paste layer (a composite material of conductive particles and resin) obtained by curing a conductive paste such as Ag paste.

[0034] The first electrode 40 has a connecting portion 41, a side electrode portion 42, an auxiliary electrode portion 43, and a mounting portion 44 (Figure 4). The connecting portion 41 is formed on the first surface 220a of the outer peripheral surface 220. The lead portion 30a of the coil 30 is connected to the connecting portion 41. A small gap is formed between the upper end of the connecting portion 41 and the upper end of the first surface 220a, but the connecting portion 41 may be formed without any gaps over the entire first surface 220a. Preferably, the length of the connecting portion 41 in the Z-axis direction is greater than half the length of the outer peripheral surface 220 of the second flange portion 22 in the Z-axis direction (thickness of the second flange portion 22). The same applies to the side electrode portion 42 and the auxiliary electrode portion 43.

[0035] As shown in Figure 5A, the thickness of the connecting wire portion 41 decreases as it approaches the intersection (corner) of the first surface 220a of the second flange portion 22 and the clockwise adjacent surface (second surface 220b). In other words, the connecting wire portion 41 has a tapered shape in which the thickness gradually decreases along the circumferential direction of the second flange portion 22 toward the side electrode portion 42.

[0036] Furthermore, the thickness of the connecting portion 41 decreases as it approaches the intersection of the first surface 220a of the second flange portion 22 and the surface adjacent to it in a counterclockwise direction. That is, the connecting portion 41 has a tapered shape in which the thickness gradually decreases along the circumferential direction of the second flange portion 22 toward one end in the extending direction of the first electrode 40.

[0037] As shown in Figure 2, the side electrode portion 42 is formed on the second surface 220b adjacent to the first surface 220a of the second flange portion 22. That is, the side electrode portion 42 is formed on a surface different from the surface on which the splice portion 41 is formed. The side electrode portion 42 acts as a fillet forming portion, and when the coil device 10 is solder-mounted to a mounting substrate, for example, a solder fillet is formed on the side electrode portion 42. The solder fillet formed on the side electrode portion 42 is to be inspected during the visual inspection of the coil device 10 after solder mounting.

[0038] The side electrode portion 42 is continuously (integrally) connected to the connecting wire portion 41 and extends along the X-axis direction at a predetermined angle (the angle between the first surface 220a and the second surface 220b) relative to the connecting wire portion 41. Because the side electrode portion 42 and the connecting wire portion 41 are continuously connected, the intersection of the first surface 220a and the second surface 220b of the second flange portion 22 is covered by the first electrode 40. A small gap is formed between the upper end of the side electrode portion 42 and the upper end of the second surface 220b, but the side electrode portion 42 may be formed without any gaps over the entire second surface 220b (except for the position of the recess 420 described later).

[0039] The auxiliary electrode portion 43 is formed on the third surface 220c adjacent to the second surface 220b of the second flange portion 22. That is, the auxiliary electrode portion 43 is formed on a surface different from the surface on which the side electrode portion 42 is formed. When the coil device 10 is solder-mounted to a mounting substrate, for example, a solder fillet may be formed on the auxiliary electrode portion 43.

[0040] The auxiliary electrode portion 43 is located on the opposite side of the X-axis from the connecting wire portion 41 and has the same shape as the connecting wire portion 41. The auxiliary electrode portion 43 is continuously (integrally) connected to the side electrode portion 42 and extends from the side electrode portion 42 at a predetermined angle (the angle between the second surface 220b and the third surface 220c). Because the auxiliary electrode portion 43 and the side electrode portion 42 are continuously connected, the intersection of the second surface 220b and the third surface 220c of the second flange portion 22 is covered by the first electrode 40. Detailed illustration is omitted, but a small gap is formed between the upper end of the auxiliary electrode portion 43 and the upper end of the third surface 220c. However, the auxiliary electrode portion 43 may be formed without any gaps across the entire third surface 220c.

[0041] As shown in Figure 5A, the thickness of the auxiliary electrode portion 43 decreases as it approaches the intersection of the third surface 220c of the second flange portion 22 and the counterclockwise adjacent surface (second surface 220b). In other words, the auxiliary electrode portion 43 has a tapered shape in which its thickness gradually decreases along the circumferential direction of the second flange portion 22 toward the side electrode portion 42.

[0042] Furthermore, the thickness of the auxiliary electrode portion 43 decreases as it approaches the intersection of the third surface 220c of the second flange portion 22 and the adjacent surface in a clockwise direction. That is, the auxiliary electrode portion 43 has a tapered shape in which its thickness gradually decreases along the circumferential direction of the second flange portion 22 toward the other end in the extending direction of the first electrode 40.

[0043] As shown in Figure 4, a mounting portion 44 is formed on the outer end surface 221 of the second flange portion 22. The mounting portion 44 has a predetermined width in the Y-axis direction and extends along the X-axis direction from one end to the other in the X-axis direction of the outer end surface 221. The mounting portion 44 serves as a connection portion to the mounting substrate, and the coil device 10 can be mounted on the mounting substrate via the mounting portion 44.

[0044] As shown in Figures 4 and 5A, the second electrode 50 has a connecting portion 51, a side electrode portion 52, an auxiliary electrode portion 53, and a mounting portion 54. The connecting portion 51 is formed on the fourth surface 220d of the second flange portion 22, the side electrode portion 52 is formed on the fifth surface 220e, and the auxiliary electrode portion 53 is formed on the sixth surface 220f. The shape and function of the connecting portion 51, the side electrode portion 52, the auxiliary electrode portion 53, and the mounting portion 54 are the same as those of the connecting portion 41, the side electrode portion 42, the auxiliary electrode portion 43, and the mounting portion 44, respectively, so a detailed explanation thereof is omitted.

[0045] As shown in Figure 2, the lead-out portion 30b of the coil 30 is connected to the connecting portion 51. The lead-out portion 30b is drawn out on the same side (positive X-axis direction) as the lead-out portion 30a. Therefore, the connecting portion 51 is located on the same side (positive X-axis direction) as the connecting portion 41. However, the direction of the lead-out portion 30b may be on the opposite side in the X-axis direction from the direction of the lead-out portion 30a. In this case, the auxiliary electrode portion 53 of the second electrode 50 may function as the connecting portion.

[0046] In this embodiment, the shape of the side electrode portion 42 of the first electrode 40 (and the same applies to the side electrode portion 52 of the second electrode 50) has distinctive features, as will be explained below. As shown in Figure 2, the side electrode portion 42 has a recess 420. The recess 420 is formed on the upper edge (upper end) of the side electrode portion 42 and is recessed along the Z-axis toward the outer end surface 221 of the second flange portion 22.

[0047] The recess 420 is formed in the central part of the first electrode 40 (side electrode portion 42) in the extending direction (X-axis direction). Here, the central part of the first electrode 40 (side electrode portion 42) in the X-axis direction corresponds to position P, which is the position where the outer circumferential surface of the coil 30 is closest to the outer circumferential surface 220 of the second flange portion 22. In other words, position P is the position where the distance between the outer circumferential surface of the coil 30 and the outer circumferential surface 220 of the second flange portion 22 is smallest.

[0048] In this embodiment, a recess 420 is provided in the side electrode portion 42 in order to increase the distance between the side electrode portion 42 and the outer circumferential surface of the coil 30 at position P. Therefore, the recess 420 is recessed in the direction away from the outer circumferential surface of the coil 30 at position P. This makes it possible to reduce the risk of contact between the side electrode portion 42 and the outer circumferential surface of the coil 30, or the risk of contact between the solder fillet formed on the side electrode portion 42 and the outer circumferential surface of the coil 30.

[0049] The recess 420 is provided in a different position (surface) from the connecting portion 41. By providing the connecting portion 41 in a different position from the recess 420, it becomes possible to secure a sufficient electrode width of the connecting portion 41 along the Z-axis direction, and the lead portion 30a of the coil 30 can be reliably connected to the connecting portion 41.

[0050] As shown in Figure 3A, the depth of the recess 420 gradually increases towards the center of the side electrode portion 42 in the X-axis direction. The ratio D1 / L1 of the depth D1 of the recess 420 to the length L1 of the side electrode portion 42 in the Z-axis direction is preferably 1 / 20 to 1 / 4, and more preferably 1 / 20 to 1 / 6. By setting the range of D1 / L1 to the above range, the risk of contact between the first electrode 40 and the outer surface of the coil 30, or the risk of contact between the solder fillet formed on the side electrode portion 42 and the outer surface of the coil 30, can be reduced. The ratio of the depth D1 of the recess 420 to the thickness of the second flange portion 22 may also be set within the above range.

[0051] The bottom surface 421 of the recess 420 consists of a curved surface that curves in a roughly C-shape (arc-shape). The bottom surface 421 is located above the center in the Z-axis direction of the second surface 220b of the second flange portion 22. At the bottom of the recess 420 (the position where the depth D1 of the recess 420 is at its maximum), the length of the first electrode 40 in the Z-axis direction (height of the first electrode 40) is greater than half the length of the second flange portion 22 in the Z-axis direction (thickness of the second flange portion 22).

[0052] As shown in Figure 2, the end of the recess 420 on the positive X-axis side is located at a predetermined distance in the negative X-axis direction from the intersection of the first surface 220a and the second surface 220b of the second flange 22. Also, the end of the recess 420 on the negative X-axis side is located at a predetermined distance in the positive X-axis direction from the intersection of the third surface 220c and the second surface 220b of the second flange 22.

[0053] As shown in Figure 3A, the width W1 of the recess 420 in the X-axis direction is smaller than the width W2 of the second flange portion 22 in the X-axis direction. Also, the width W1 of the recess 420 in the X-axis direction is smaller than the width of the second surface 220b of the second flange portion 22 in the X-axis direction. The ratio W1 / W2 of the width W1 of the recess 420 in the X-axis direction to the width W2 of the second flange portion 22 in the X-axis direction is preferably 1 / 6 to 1 / 3. By setting the range of W1 / W2 to the above range, the risk of contact between the first electrode 40 and the outer surface of the coil 30, or the risk of contact between the solder fillet formed on the side electrode portion 42 and the outer surface of the coil 30, can be effectively reduced. Note that the ratio of the width W1 of the recess 420 in the X-axis direction to the width of the second surface 220b of the second flange portion 22 in the X-axis direction may also be set within the above range.

[0054] As shown in Figure 2, at the location of the recess 420, an electrode-free region 425 is provided between the intersection of the inner end surface 222 and the outer circumferential surface 220 of the second flange portion 22 and the first electrode 40 (side electrode portion 42), where the side electrode portion 42 is substantially not formed. The electrode-free region 425 has a convex shape defined by the recess 420 (bottom surface 421) and protrudes toward the outer end surface 221.

[0055] The electrode-free region 425 is formed on the outer surface 220 as a result of providing the recess 420 in the first electrode 40. Therefore, the length of the electrode-free region 425 in the Z-axis direction corresponds to the depth of the recess 420, and the width of the electrode-free region 425 in the X-axis direction corresponds to the width of the recess 420 in the X-axis direction. Furthermore, the lower end of the electrode-free region 425 corresponds to the upper end of the side electrode portion 42.

[0056] Thus, when an electrode-free region 425 is formed on the outer circumferential surface 220, the electrode-free region 425 is interposed between the outer circumferential surface of the coil 30 and the side electrode portion 42 at the location of the recess 420. Therefore, it is possible to increase the distance (insulation distance) between the side electrode portion 42 and the outer circumferential surface of the coil 30 by an amount corresponding to the size of the electrode-free region 425. Thus, the risk of the outer circumferential surface of the coil 30 coming into contact with the side electrode portion 42 can be effectively reduced.

[0057] Furthermore, at the location of the recess 420, an electrode-free region 425 is interposed between the inner end surface 222 of the second flange portion 22 and the side electrode portion 42. Therefore, the distance between the side electrode portion 42 and the inner end surface 222 can be increased along the Z-axis direction by an amount corresponding to the width of the electrode-free region 420. Consequently, a portion of the solder fillet formed on the side electrode portion 42 is less likely to ride up onto the inner end surface 222, effectively reducing the risk of the outer surface of the coil 30 coming into contact with the solder fillet.

[0058] In addition, it is preferable that the side electrode portion 42 is not present in the electrode-free region 425, but a small amount (negligible amount) of the side electrode portion 42 may be present. For example, a part of the side electrode portion 42 may be present in the electrode-free region 425 with an extremely thin thickness that does not contribute to the formation of the solder fillet.

[0059] As shown in Figure 5A, the side electrode portion 42 has a thin portion 422 and a thick portion 423. The thin portion 422 and the thick portion 423 are continuously (integrally) connected. The thin portion 422 is formed in the central part of the extending direction (X-axis direction) of the side electrode portion 42, i.e., at the position of the recess 420, and is recessed toward the center of the second flange portion 22 (axis of the winding core portion 23). The surface of the thin portion 422 has a roughly C-shape (arc-shaped) when viewed from the Z-axis direction. The thinnest part of the thin portion 422 is located approximately in the center of the side electrode portion 42 in the X-axis direction.

[0060] The thickness of the thin portion 422 (side electrode portion 42) decreases as it approaches the center in the direction of extension of the side electrode portion 42 (X-axis direction). In other words, the thickness of the side electrode portion 42 decreases as it approaches the recess 420. Therefore, the thin portion 422 has a tapered shape in which the thickness gradually decreases towards the center in the X-axis direction of the side electrode portion 42. As shown in Figure 6A, the ratio T1 / T2 of the thickness T1 of the thin portion 422 to the thickness T2 of the thick portion 423 is preferably 1 / 2 to 9 / 10.

[0061] By setting the above ratio T1 / T2 to the above range, the protrusion of the side electrode portion 42 from the outer peripheral surface 220 of the second flange portion 22 at the position of the recess 420 is suppressed, and the risk of the outer peripheral surface of the coil 30 coming into contact with the side electrode portion 42 or the solder fillet attached thereto can be reduced. In particular, by reducing the thickness of the side electrode portion 42 toward the center in the X-axis direction of the side electrode portion 42, it becomes possible to form a thin-walled portion 422 with a small electrode thickness over a wide area along the X-axis direction, centered on the center of the side electrode portion 42 in the X-axis direction. This effectively reduces the risk of the outer peripheral surface of the coil 30 coming into contact with the side electrode portion 42 or the solder fillet attached thereto.

[0062] The thickened portion 423 is formed on the outer side of the thinned portion 422 (recess 420) in the X-axis direction. The side electrode portion 42 is provided with two thickened portions 423 such that the thinned portion 422 is located between them. The thickness of the thinned portion 422 is smaller than the thickness of the thickened portion 423. The thickened portion 423 protrudes outward in the Y-axis direction of the second flange portion 22 and has a convex shape. The surface of the thickened portion 423, when viewed from the Z-axis direction, has a roughly C-shape (arc-shaped).

[0063] The thickness of the thickened portion 423 decreases as it approaches the auxiliary electrode portion 43 (or the intersection of the second surface 220b and the third surface 220c of the second flange portion 22). Furthermore, the thickness of the thickened portion 423 decreases as it approaches the joint portion 41 (or the intersection of the second surface 220b and the first surface 220a of the second flange portion 22). Also, the thickness of the thickened portion 423 decreases as it approaches the thinned portion 422. In other words, each thickened portion 423 of the side electrode portion 42 has a tapered shape in which the thickness gradually decreases toward the positive X-axis direction and the negative X-axis direction. By providing the side electrode portion 42 with thickened portions 423, it is possible to effectively prevent defects at the corners between the first surface 220a and the second surface 220b of the second flange portion 22, or at the corners between the second surface 220b and the third surface 220c.

[0064] In the side electrode portion 42 (particularly at the location of the recess 420), it is preferable that the thickness (maximum thickness or average thickness) of the first electrode 40 is smaller than that of the connecting portion 41. The thickness of the connecting portion 41 is preferably 25 μm or more. In this case, the reliability of the connection between the coil 30's lead portion 30a and the connecting portion 41 can be improved.

[0065] As shown in Figure 5B, the thickness of the side electrode portion 42 decreases towards the inner end surface 222 side of the second flange portion 22. As shown in Figures 6A and 6B, on the outer end surface 221 side of the second surface 220b of the second flange portion 22 (see Figure 6A), both the thin portion 422 and the thick portion 423 are thinner compared to the inner end surface 222 side of the second surface 220b (see Figure 6B). However, as shown in Figure 6B, the thickness of the thin portion 422 is virtually zero.

[0066] As described above, the side electrode portion 42 is provided with a tapered portion 424 (Figure 5B) whose thickness gradually decreases toward the inner end surface 222. At the location of the thin-walled portion 422 shown in Figure 5A, the tapered portion 424 is formed in the region between the outer end surface 221 of the second flange portion 22 and the electrode-free region 425. At the location of the thick-walled portion 423 shown in Figure 5A, the tapered portion 424 is formed from the outer end surface 221 of the second flange portion 22 to the vicinity of the inner end surface 222. Note that the above tapered shape may be formed not only on the side electrode portion 42, but also on the connecting wire portion 41 and the auxiliary electrode portion 43.

[0067] The side electrode portion 52 of the second electrode 50 has a recess (not shown) similar to the recess 420 formed in the side electrode portion 42 of the first electrode 40. Also, as shown in Figures 5A and 5B, the side electrode portion 52 has a thin portion 522, a thick portion 523, a tapered portion 524, and an electrode-free region 525. The shape of the side electrode portion 52 of the second electrode 50 is the same as the shape of the side electrode portion 42 of the first electrode 40, so a detailed explanation is omitted.

[0068] Next, the manufacturing method of the coil device 10 will be described. First, a drum-shaped core 20 as shown in Figure 2 is prepared. Next, a first electrode 40 and a second electrode 50 are formed on the outer peripheral surface 220 and the outer end surface 221 of the second flange portion 22 of the core 20. The first electrode 40 is formed, for example, by applying electrode material to the outer peripheral surface 220 (first surface 220a, second surface 220b, third surface 220c) and the outer end surface 221 of the second flange portion 22 using a brush. At this time, the electrode material is applied to the second surface 220b so as to give the shape of the recess 420 as shown in Figure 2. Alternatively, the first electrode 40 may be formed by the dip method. A detailed explanation will be omitted, but when forming the first electrode 40 by the dip method, the desired operation is performed using a jig or the like so as to give the shape of the recess 420 as shown in Figure 2. The same applies to the formation of the second electrode 50.

[0069] Next, the coil 30 is wound around the core 23 (Figure 5A), and the lead-out portion 30a of the coil 30 is connected to the joint portion 41 of the first electrode 40, for example, by thermocompression bonding. The lead-out portion 30b of the coil 30 is also connected to the joint portion 51 of the second electrode 50, for example, by thermocompression bonding. Next, as shown in Figure 1, the outer resin 60 is applied between the first flange portion 21 and the second flange portion 22 so as to cover the outer surface of the coil 30, and then cured. The outer resin 60 may contain metal powder or the like. Through the above steps, the coil device 10 can be manufactured.

[0070] As described above, in the coil device 10 of this embodiment, the side electrode portion 42 shown in Figure 2 has a recess 420 that is recessed toward the outer end surface 221 side of the second flange portion 22. Therefore, at the location of the recess 420, the side electrode portion 42 is formed at a distance corresponding to the degree of recession of the recess 420 from the outer circumferential surface of the coil 30. This reduces the risk of contact between the outer circumferential surface of the coil 30 and the side electrode portion 42, and prevents short-circuit failures from occurring between the coil 30 and the side electrode portion 42.

[0071] Furthermore, at the location of the recess 420, the side electrode portion 42 is formed at a distance along the Z-axis direction corresponding to the degree of recess 420, away from the inner end surface 222 of the second flange portion 22. Therefore, when solder fillet adheres to the side electrode portion 42, it becomes less likely for a portion of the solder fillet to ride up (wrap around) onto the inner end surface 222. This reduces the risk of contact between the outer surface of the coil 30 and the solder fillet, and prevents short-circuit defects from occurring between the coil 30 and the solder fillet.

[0072] Furthermore, when forming the side electrode portion 42 on the outer peripheral surface 220 of the second flange portion 22, applying the electrode material to the outer peripheral surface 220 in such a way that a recess 420 is formed can prevent the electrode material from unintentionally riding up onto the inner end surface 222.

[0073] Furthermore, the side electrode portion 42 extends in the X-axis direction along the outer circumference of the second flange portion 22, and the recess 420 is formed in the central part of the side electrode portion 42 in the X-axis direction. Therefore, it is possible to form the recess 420 over a wide area along the X-axis direction, centered on the central part of the side electrode portion 42 in the X-axis direction. Thus, the risk of the outer surface 30 of the coil coming into contact with the side electrode portion 42 or the solder fillet attached thereto can be effectively reduced.

[0074] Furthermore, typically, the side electrode portion 42 and the outer surface of the coil 30 are positioned closest together, particularly in the central part of the side electrode portion 42 in the X-axis direction (see position P in Figure 2). Therefore, by forming a recess 420 in the central part of the side electrode portion 42 in the X-axis direction, the risk of the outer surface of the coil 30 coming into contact with the side electrode portion 42 or the solder fillet attached thereto can be effectively reduced.

[0075] Furthermore, as shown in Figure 5B, the thickness of the side electrode portion 42 decreases as it approaches the inner end surface 222 of the second flange portion 22. Therefore, the closer to the coil 30, the less the side electrode portion 42 protrudes outward in the Y-axis direction from the outer peripheral surface 220 of the second flange portion 22, effectively reducing the risk of the outer peripheral surface of the coil 30 contacting the side electrode portion 42. Also, the closer to the coil 30, the less the solder fillet formed on the side electrode portion 42 protrudes outward in the Y-axis direction, effectively reducing the risk of the outer peripheral surface of the coil 30 contacting the solder fillet. In addition, a portion of the solder fillet formed on the side electrode portion 42 is less likely to ride up onto the inner end surface 222 of the second flange portion 22, and in this respect as well, the risk of the outer peripheral surface of the coil 30 contacting the solder fillet can be effectively reduced.

[0076] It should be noted that the present invention is not limited to the embodiments described above, and can be modified in various ways within the scope of the present invention.

[0077] In the above embodiment, an example of applying the present invention to an inductor was described, but the present invention may also be applied to coil devices other than inductors (for example, transformers).

[0078] In the above embodiment, as shown in Figure 2, the side electrode portion 42 was provided with one recess 420, but it may be provided with multiple recesses 420. The same applies to the second electrode 50.

[0079] In the above embodiment, as shown in Figure 2, the lead portion 30a was connected to the connecting wire portion 41 formed on the first surface 220a of the second flange portion 22, but it may also be connected to the side electrode portion 42 formed on the second surface 220b. In this case, the connecting wire portion 41 can be omitted. However, it is preferable that the lead portion 30a is formed at a position different from the position of the recess 420 (for example, the thickened portion 423 shown in Figure 5A). The same applies to the lead portion 30b.

[0080] In the above embodiment, the auxiliary electrode portion 43 may be omitted from the first electrode 40. Similarly, the auxiliary electrode portion 53 may be omitted from the second electrode 50. [Explanation of Symbols]

[0081] 10... Coil device 20...core 21...First guard section 22...Second guard section 220...Outer surface 221...outer end surface 222...Inner end surface 23...Core section 30... Coil 30a, 30b... Lead section 40…1st electrode 41...Connection section 42...Side electrode part 420···recess 421...Bottom 422...thin section 423...Thick part 424...Tapered section 425…electrode non-formation area 43...Auxiliary electrode part 44. Implementation Section 50…Second electrode 51...Connection section 52...Side electrode part 522...thin section 523...Thick part 524...Tapered section 525…electrode non-formation area 53...Auxiliary electrode section 54. Implementation Section 60... Exterior resin

Claims

1. A core having a winding core portion arranged substantially perpendicular to the mounting surface and a flange portion formed at one end of the winding core portion in the axial direction, The coil arranged in the aforementioned winding core, The lead portion of the coil is connected to an electrode, which at least a part of which is formed on the outer surface of the flange portion, The electrode has a recess that is recessed toward the outer end surface side of the flange portion, The electrode extends along the outer circumference of the flange portion, A coil device in which the thickness of the electrode decreases as it approaches the center in the direction of extension of the electrode.

2. At the location of the recess, an electrode-free region is provided between the electrode and the intersection of the inner end surface and the outer circumferential surface of the flange. The coil device according to claim 1, wherein the electrode is not formed in the electrode-free region.

3. The electrode extends along the outer circumference of the flange portion, The coil device according to claim 1 or 2, wherein the recess is formed in the central part of the electrode in the extending direction.

4. The coil device according to any one of claims 1 to 3, wherein the thickness of the electrode decreases toward the inner end face side of the flange portion.

5. The electrode has a connecting portion to which the lead portion of the coil is connected. The coil device according to any one of claims 1 to 4, wherein the connecting portion is provided at a position different from the position of the recess.

6. When viewed from the axial direction of the winding core, the flange portion has a polygonal shape. The outer circumferential surface of the flange portion has a plurality of surfaces adjacent to each other, The electrode spans across multiple surfaces, The coil device according to claim 5, wherein the connecting portion is formed on a surface different from the surface on which the recess is formed.

7. The coil device according to claim 5 or 6, wherein the thickness of the electrode is smaller at the location of the recess compared to the location of the connecting wire portion.

8. The coil device according to any one of claims 1 to 7, wherein the electrode contains metal and glass.

9. A core having a winding core portion arranged substantially perpendicular to the mounting surface and a flange portion formed at one end of the winding core portion in the axial direction, The coil arranged in the aforementioned winding core, The lead portion of the coil is connected to an electrode, which at least a part of which is formed on the outer surface of the flange portion, The electrode has a recess that is recessed toward the outer end surface side of the flange portion, The thickness of the electrode decreases towards the inner end face side of the flange portion in this coil device.

10. A core having a winding core portion arranged substantially perpendicular to the mounting surface and a flange portion formed at one end of the winding core portion in the axial direction, The coil arranged in the aforementioned winding core, The lead portion of the coil is connected to an electrode, which at least a part of which is formed on the outer surface of the flange portion, The electrode has a recess that is recessed toward the outer end surface side of the flange portion, The electrode has a connecting portion to which the lead portion of the coil is connected. The aforementioned connecting portion is provided at a position different from the position of the recess, A coil device in which the thickness of the electrode is smaller at the location of the recess compared to the location of the connecting wire portion.

11. A core having a winding core portion arranged substantially perpendicular to the mounting surface and a flange portion formed at one end of the winding core portion in the axial direction, The coil arranged in the aforementioned winding core, The lead portion of the coil is connected to an electrode, which at least a part of which is formed on the outer surface of the flange portion, The electrode has a recess that is recessed toward the outer end surface side of the flange portion, The electrode has a connecting portion to which the lead portion of the coil is connected. When viewed from the axial direction of the winding core, the flange portion has a polygonal shape. The outer circumferential surface of the flange portion has a plurality of surfaces adjacent to each other, The electrode spans across multiple surfaces, The aforementioned connecting portion is formed on a surface different from the surface on which the recess is formed. A coil device in which the thickness of the electrode is smaller at the location of the recess compared to the location of the connecting wire portion.

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