Coil component, wire joining method, and coil component manufacturing method

Abstract

To prevent a wire from breaking at a joint portion and at a boundary between the joint portion and a linear portion.SOLUTION: A coil component includes a core, a wire, and external electrodes 40. The core has a winding core portion and a pair of flange portions. A specific axis perpendicular to a central axis is defined to be a first axis X, one of the directions along the first axis X is defined as a first positive direction X1, and an opposite direction to the first positive direction X1 is defined as a first negative direction X2. The external electrodes 40 each cover an outer surface of the flange portion facing the first positive direction X1. The wire includes: a linear portion wound around the winding core portion; and a joint portion 51 located at each end of the wire and connected to each of the external electrodes. In a cross section perpendicular to the central axis and including the joint portion 51, an end of the joint portion 51 on the first negative direction X2 side is located on the first negative direction X2 side with respect to an end of the external electrode 40 on the first positive direction X1 side. Moreover, a dimension P1 in a direction along the first axis X from the end of the joint portion 51 on the first negative direction X2 side to the end thereof on the first positive direction X1 side is larger than a wire diameter of the linear portion.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a coil component, a wire joining method, and a method for manufacturing a coil component. [Background technology]

[0002] The coil component described in Patent Document 1 includes a core. The core has a winding core portion and two flange portions. The winding core portion is in the shape of a rectangular prism. The two flange portions are connected to both ends of the winding core portion. Each flange portion protrudes outward from an outer surface of the winding core portion in a direction perpendicular to the central axis of the winding core portion. The coil component also includes a first external electrode and a second external electrode. The first external electrode is located on an upper surface of one of the flange portions. The second external electrode is located on an upper surface of the other flange portion. The coil component also includes a wire. The wire is a coated conductor. The wire is wound around the winding core portion. A first end of the wire is thermocompression bonded to the first external electrode. A second end of the wire is thermocompression bonded to the second external electrode. The thermocompression is performed by crimping a heater chip onto the wire. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-294307 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a coil component such as that described in Patent Document 1, when the end of the wire is joined to an external electrode, heat and pressure are applied to the end of the wire, causing the end of the wire to be crushed and thinned. External forces tend to concentrate on the thinned portion of the wire, which makes the wire prone to breakage. [Means for solving the problem]

[0005] In order to solve the above problems, the present invention provides a core having a columnar winding core and a pair of flanges connected to ends of the winding core in a direction along the central axis, a wire wound around the winding core, and an external electrode covering an outer surface of the flange, wherein when a specific axis perpendicular to the central axis is defined as a first axis, one of the directions along the first axis is defined as a positive direction, and a direction opposite to the positive direction is defined as a negative direction, the flange protrudes toward the positive direction with respect to the outer surface of the winding core, and the external electrode is disposed on the outer surface of the flange that is adjacent to the positive direction. a coil component having a surface facing the first axis, the wire having a linear portion wound around the winding core portion and a joint portion located at an end of the wire and connected to the external electrode, in a cross section perpendicular to the central axis and including the joint portion, the negative end of the joint portion is located on the negative side of the positive end of the external electrode, and the dimension along the first axis from the negative end to the positive end of the joint portion is larger than the wire diameter of the linear portion.

[0006] In addition, in order to solve the above-mentioned problems, the present invention provides a wire joining method comprising: a ball portion forming process in which a ball portion having a diameter larger than the wire diameter of the linear portion before melting is formed at the end of the wire by melting the wire; and a joining process in which a joint portion connected to the external electrode is formed at the end of the wire by irradiating the ball portion with a laser while the ball portion is in contact with an external electrode covering the outer surface of a core.

[0007] In addition, in order to solve the above-mentioned problems, there is provided a method for manufacturing a coil component, the method including: a preparation step of preparing a core having a columnar winding core portion and a pair of flange portions connected to ends in a direction along the central axis of the winding core portion, the core having an external electrode covering the outer surface of the flange portions; a winding step of winding a wire around the winding core portion; a ball portion forming step of melting the wire to form a ball portion at the end of the wire having a diameter larger than the wire diameter of the linear portion before melting; and a joining step of irradiating the ball portion with a laser while the ball portion is in contact with the external electrode to form a joint at the end of the wire that is connected to the external electrode.

[0008] In the above-mentioned configuration, the thickness of the joint portion of the wire is greater than the thickness of the linear portion, so that even if a certain amount of external force acts on the joint portion, the wire is less likely to break at the joint portion and at the boundary between the joint portion and the linear portion. Effect of the Invention

[0009] This prevents the wire from breaking at the joint and at the boundary between the joint and the linear portion. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of a coil component. [Diagram 2] FIG. 2 is an enlarged view of the vicinity of the second joint when viewed in the first negative direction. [Diagram 3] FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. [Figure 4] FIG. 4 is a diagram illustrating a manufacturing method of the coil component. [Diagram 5] FIG. 5 is a diagram illustrating a method for manufacturing the coil component. [Figure 6] FIG. 6 is a diagram illustrating a method for manufacturing a coil component. [Figure 7] FIG. 7 is a diagram illustrating a method for manufacturing a coil component. [Figure 8] FIG. 8 is a diagram illustrating a manufacturing method of the coil component. [Figure 9] FIG. 9 is a diagram illustrating a manufacturing method of the coil component. [Figure 10] FIG. 10 is a diagram illustrating a method for manufacturing a coil component. [Figure 11] FIG. 11 is a diagram illustrating a manufacturing method of the coil component. [Figure 12] FIG. 12 is a diagram illustrating a method for manufacturing a coil component. [Figure 13] FIG. 13 is a diagram illustrating a manufacturing method of the coil component. [Figure 14] FIG. 14 is a cross-sectional view of a coil device according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of a coil component will be described with reference to the drawings. Note that the drawings may show components enlarged for ease of understanding. The dimensional ratios of the components may differ from those in the actual drawings or from those in other drawings.

[0012] <Overall structure> As shown in FIG. 1, the coil device 10 includes a core 10C and a top plate 12. The core 10C includes a columnar winding core portion 11, a first flange portion 21, and a second flange portion 22. In the following description, when there is no need to distinguish between the first flange portion 21 and the second flange portion 22, they may be collectively referred to as the flange portion 20.

[0013] The winding core 11 is in the shape of a quadrangular prism. A cross section perpendicular to the central axis C of the winding core 11 is in the shape of a rectangle. Note that the "rectangular shape" referred to here may be any shape having four sides and being rectangular overall, and may also include a rectangular shape with chamfered corners. The material of the winding core 11 is a non-conductive material. Specifically, the material of the winding core 11 is, for example, Ni-Zn ferrite, alumina, synthetic resin, a mixture thereof, or the like.

[0014] Here, a specific axis perpendicular to the central axis C of the winding core 11 is defined as the first axis X. In this embodiment, the first axis X is parallel to two of the four sides of the winding core 11 when viewed in a direction along the central axis C. An axis perpendicular to both the first axis X and the central axis C is defined as the second axis Y. In this embodiment, the second axis Y is parallel to the remaining two of the four sides of the winding core 11 when viewed in a direction along the central axis C. An axis parallel to the central axis C is defined as the third axis Z. One of the directions along the first axis X is defined as the first positive direction X1, and the opposite direction to the first positive direction X1 is defined as the first negative direction X2. Similarly, one of the directions along the second axis Y is defined as the second positive direction Y1, and the opposite direction to the second positive direction Y1 is defined as the second negative direction Y2. Moreover, one of the directions along the third axis Z is defined as a third positive direction Z1, and the direction opposite to the third positive direction Z1 is defined as a third negative direction Z2.

[0015] As shown in FIG. 1, the first flange portion 21 is connected to a first end, which is an end in the third positive direction Z1, of the winding core portion 11. The first flange portion 21 has a flat, substantially rectangular plate shape. The thickness direction of the first flange portion 21 is along the third axis Z. When viewed in the direction along the third axis Z, each side of the first flange portion 21 is parallel to each side of the winding core portion 11. In addition, the first flange portion 21 protrudes outward from the outer surface of the winding core portion 11 in the direction along the first axis X and the direction along the second axis Y. That is, the first flange portion 21 also protrudes in the first positive direction X1 side from the outer surface of the winding core portion 11.

[0016] The second flange portion 22 is connected to a second end of the winding core portion 11, which is the end on the third negative direction Z2 side. The second flange portion 22 has a shape that is plane-symmetrical to the first flange portion 21. That is, the second flange portion 22 is a substantially rectangular plate shape. The second flange portion 22 protrudes outward from the outer surface of the winding core portion 11 in the direction along the first axis X and the direction along the second axis Y. That is, the second flange portion 22 also protrudes in the first positive direction X1 side from the outer surface of the winding core portion 11.

[0017] The material of the first flange portion 21 and the second flange portion 22 is the same as that of the winding core portion 11. In addition, the first flange portion 21 and the second flange portion 22 are integrally molded with the winding core portion 11. The top plate 12 is a flat rectangular plate. The thickness direction of the top plate 12 is along the first axis X. The long side of the top plate 12 is parallel to the third axis Z. The short side of the top plate 12 is parallel to the second axis Y. The top plate 12 is located on the first negative direction X2 side with respect to the core 10C. The top plate 12 is connected to both the surface of the first flange 21 facing the first negative direction X2 side and the surface of the second flange 22 facing the first negative direction X2 side. In other words, the top plate 12 is bridged between the first flange 21 and the second flange 22. The material of the top plate 12 is the same as that of the winding core 11.

[0018] The coil component 10 includes a first external electrode 41 and a second external electrode 42. The first external electrode 41 covers the entire surface of the outer surface of the first flange 21 facing the first positive direction X1. The second external electrode 42 covers the entire surface of the outer surface of the second flange 22 facing the first positive direction X1. In the following description, the first external electrode 41 and the second external electrode 42 may be collectively referred to as external electrodes 40 when there is no need to distinguish between them.

[0019] As shown in FIG. 3, each external electrode 40 has an underlayer L0, a first layer L1, a second layer L2, and a third layer L3. The underlayer L0 is located closest to the first negative direction X2 among the layers of the external electrode 40. That is, the underlayer L0 directly covers the surface of the outer surface of the flange portion 20 facing the first positive direction X1. The underlayer L0 contains Ag. The first layer L1 covers the surface of the underlayer L0 facing the first positive direction X1. The first layer L1 contains Ni. The second layer L2 covers the surface of the first layer L1 facing the first positive direction X1. The second layer L2 contains Cu.

[0020] The third layer L3 covers the surface of the second layer L2 on the first positive direction X1 side. That is, the third layer L3 is the outermost layer of the external electrode 40. Therefore, when the base layer L0, the first layer L1, and the second layer L2 are considered as inner layers, the third layer L3 is an outer layer located on the opposite side of the inner layers from the outer surface of the flange portion 20. The third layer L3 contains Sn. The first layer L1, the second layer L2, and the third layer L3 are plating layers for the base layer L0. Note that FIG. 1 illustrates the external electrodes 40 as if there were no boundaries between these layers.

[0021] <About wire> As shown in FIG. 1, the coil device 10 includes a wire 50 wound around a winding core 11. As shown in FIG. 2, the wire 50 includes a conductor 50A and an insulating coating 50B. The conductor 50A is linear. The conductor 50A is made of, for example, Cu. In this embodiment, the diameter of the conductor 50A is about 10 μm. The insulating coating 50B covers the outer circumferential surface of the conductor 50A. The insulating coating 50B is made of a synthetic resin such as polyurethane or polyamideimide. In this embodiment, the thickness of the insulating coating 50B is about 2.5 μm. The wire 50 is substantially circular in a cross section perpendicular to the extension direction of the wire 50.

[0022] As shown in FIG. 1, the wire 50 has a first joint 51A, a second joint 51B, and a linear portion 52. In the following, when it is not necessary to distinguish between the first joint 51A and the second joint 51B, they may be collectively referred to as a joint 51. The first joint 51A is located at the end of the wire 50 on the third positive direction Z1 side. The first joint 51A is connected to the first external electrode 41. The second joint 51B is located at the end of the wire 50 on the third negative direction Z2 side. The second joint 51B is connected to the second external electrode 42. The joint 51 does not have an insulating coating 50B, and has only a conductor 50A. At least a part of the interface between the joint 51 and the third layer L3 is made of a Cu-Sn alloy. The above phrase "having only a conductor 50A" allows the presence of a trace of the insulating coating 50B. Specifically, when the joint 51 is observed in the first negative direction X2, if the proportion of the conductor 50A is 97% or more, it is determined that the joint "only has the conductor 50A."

[0023] The linear portion 52 is a portion of the wire 50 other than the joint portion 51. That is, the linear portion 52 is wound around the winding core portion 11. The linear portion 52 has an insulating coating 50B and a conductor 50A. That is, due to the dimensional relationship between the conductor 50A and the insulating coating 50B, the linear portion 52 has a wire diameter of about 15 μm.

[0024] <About the temporary fixing part of the wire> 2, linear portion 52 of wire 50 has temporary fixing portion 53. Temporary fixing portion 53 is located on the winding core portion 11 side with respect to second joint portion 51B. Moreover, temporary fixing portion 53 is adjacent to second joint portion 51B in the extension direction of wire 50.

[0025] The temporary fixing portion 53 is joined to the third layer L3 of the second external electrode 42. Specifically, the end of the temporary fixing portion 53 on the first negative direction X2 side is located on the first negative direction X2 side with respect to the end of the third layer L3 on the first positive direction X1 side. That is, the temporary fixing portion 53 is at least partially embedded in the second external electrode 42 with the insulating coating 50B being provided thereon.

[0026] <Dimensional relationship between external electrodes and wires> A description will be given of the dimensional relationship between each external electrode 40 and each joint portion 51. In the following, the dimensional relationship between the second external electrode 42 and the second joint portion 51B will be representatively described, but the dimensional relationship between the first external electrode 41 and the first joint portion 51A is also similar.

[0027] As shown in FIG. 3, assume that the cross section is taken along a specific cross section orthogonal to the central axis C and including the second joint portion 51B. The second joint portion 51B is embedded in the second external electrode 42. That is, the end of the second joint portion 51B on the first negative direction X2 side is located on the first negative direction X2 side with respect to the end of the second external electrode 42 on the first positive direction X1 side. In particular, the entire second joint portion 51B is embedded in the second external electrode 42. Specifically, in the direction along the first axis X, the end of the second joint portion 51B on the first positive direction X1 side coincides with the end of the second external electrode 42 on the first positive direction X1 side.

[0028] An end face of the second joint portion 51B on the first positive direction X1 side is a flat surface parallel to the second axis Y and the central axis C. In addition, the end face of the second joint portion 51B on the first positive direction X1 side is substantially flush with the end of the second external electrode 42 on the first positive direction X1 side.

[0029] The end of the second external electrode 42 on the first positive direction X1 side is determined by acquiring the contour of the second external electrode 42 in a specific cross section through image processing using an electron microscope. Then, the point of the contour that is located furthest in the first positive direction X1 is determined as the end of the second external electrode 42 on the first positive direction X1 side.

[0030] In the above-described specific cross section, the end of the second joint 51B on the first negative direction X2 side is located on the first positive direction X1 side with respect to the end of the second layer L2 on the first positive direction X1 side. That is, the second joint 51B is located in the third layer L3 and does not reach the second layer L2.

[0031] In the specific cross section, the dimension P1 along the first axis X from the end of the second joint 51B on the first negative direction X2 side to the end on the first positive direction X1 side is about 21 μm. That is, the dimension P1 along the first axis X from the end of the second joint 51B on the first negative direction X2 side to the end on the first positive direction X1 side is larger than the wire diameter of the linear portion 52.

[0032] In the specific cross section, a portion of the second joint 51B that is located on the first negative direction side with respect to the end of the second external electrode 42 on the first positive direction X1 side is defined as a buried portion 54. In this embodiment, a portion of the second joint 51B in the specific cross section excluding the end face on the first positive direction X1 side corresponds to the buried portion 54. In the specific cross section, the maximum dimension of the buried portion 54 in the direction along the second axis Y is defined as a first dimension A1. The first dimension A1 is approximately 63 μm. Therefore, the first dimension A1 is larger than the wire diameter of the linear portion 52.

[0033] Further, the dimension of the buried portion 54 in the direction along the second axis Y on the first positive direction X1 side with respect to the location of the first dimension A1 is defined as a second dimension A2. The second dimension A2 is smaller than the first dimension A1.

[0034] <About the manufacturing method of coil parts> 4, the method for manufacturing coil component 10 includes a preparation step S11, a first end ball portion forming step S12, a first end pressing step S13, a first end joining step S14, a first end removing step S15, and a winding step S16. The method for manufacturing coil component 10 also includes a second end temporary pressing step S17, a second end temporary fixing step S18, a wire cutting step S19, a second end ball portion forming step S20, a second end pressing step S21, a second end joining step S22, and a second end removing step S23.

[0035] Among the above steps, the steps from the first end ball portion forming step S12 to the first end removing step S15, and the steps from the second end provisional pressing step S17 to the second end removing step S23 are steps related to the joining method of the wire 50.

[0036] First, a preparation step S11 is performed. In the preparation step S11, a core 10C on which an external electrode 40 is formed is prepared. The core 10C is formed by mixing Ni-Zn ferrite powder with a synthetic resin binder and firing a molded body formed by press molding. As a result, the core 10C having the winding core portion 11, the first flange portion 21, and the second flange portion 22 described above is formed. Then, a conductive paste containing Ag is applied to the surface of the first flange portion 21 of the core 10C facing the first positive direction X1. The paste is evaporated to form a base layer L0. Furthermore, electroplating is performed on the base layer L0 to form a first layer L1, a second layer L2, and a third layer L3. As a result, a first external electrode 41 is formed. Similarly, a second external electrode 42 is formed on the surface of the second flange portion 22 facing the first positive direction X1. Then, the core 10C on which the external electrodes 40 are formed is clamped by a pair of rotary chucks RC from the outside of each flange portion 20. This allows the core 10C to be supported rotatably around the central axis C as the center of rotation.

[0037] Next, a first-end ball portion forming step S12 is performed. Prior to the first-end ball portion forming step S12, the first end of the wire 50 has a conductor 50A and an insulating coating 50B. As shown in FIG. 5, in the first-end ball portion forming step S12, a laser is irradiated to the first end of the wire 50. In the irradiated portion, the insulating coating 50B melts, thereby exposing the conductor 50A. Then, as shown in FIG. 6, in the irradiated portion, the conductor 50A melts to form a substantially spherical ball portion BP having a diameter larger than the wire diameter of the linear portion 52. In this state, some of the insulating coating 50B may remain on the surface.

[0038] Next, a first end pressing step S13 is performed. As shown in Fig. 6, in the first end pressing step S13, the ball portion BP is pressed against the first external electrode 41 using a transparent member CP made of a material that transmits the laser. Specifically, the ball portion BP is sandwiched between the transparent member CP and the first external electrode 41. The transparent member CP may be made of any material that transmits the laser, such as borosilicate glass or sapphire glass. Note that by pressing the transparent member CP against the ball portion BP, the insulating coating 50B remaining on the ball portion BP is welded to the transparent member CP.

[0039] Next, a first end joining step S14 is performed. As shown in FIG. 7, in the first end joining step S14, the ball part BP is sandwiched between the transparent member CP and the first external electrode 41, and a laser is irradiated onto the ball part BP from the side of the transparent member CP. Therefore, in this state, the ball part BP is in contact with the first external electrode 41. As a result, a first joint part 51A connected to the first external electrode 41 is formed at the first end of the wire 50. In addition, the ball part BP is embedded in the melted and softened third layer L3 by the pressing force of the transparent member CP, and thus a buried part 54 is formed. In addition, the end surface of the first joint part 51A in the first positive direction X1 is formed as a flat surface by the pressing force of the transparent member CP.

[0040] Next, a first end removing step S15 is performed. In the first end removing step S15, the transparent member CP is removed from the wire 50. In this first end removing step S15, the insulating coating 50B remaining on the ball portion BP is removed from the wire 50 together with the transparent member CP.

[0041] Next, a winding step S16 is performed. In the winding step S16, the core 10C is rotated together with the rotary chuck RC about the central axis C, and the wire 50 is wound around the winding core portion 11. Next, a second end temporary pressing step S17 is performed. As shown in Fig. 8, in the second end temporary pressing step S17, the wire 50 is pulled out from the portion where it is wound around the winding core portion 11, and the wire 50 is positioned on the second external electrode 42. Then, the wire 50 is sandwiched between the transparent member CP and the second external electrode 42. This temporarily determines the position of the wire 50.

[0042] Next, the second end temporarily fixing step S18 is performed. As shown in FIG. 9, in the second end temporarily fixing step S18, a laser is irradiated from the side of the transparent member CP to the temporarily fixed portion of the second external electrode 42. As a result, the temporary fixing portion 53 on the winding core portion 11 side is joined to the temporary fixing portion of the wire 50 at the location where the second joint portion 51B is to be formed. At this time, the third layer L3 melts at the temporary fixing portion irradiated with the laser. Then, the temporary fixing portion 53 of the wire 50 is pressed against the melted temporary fixing portion, so that the temporary fixing portion 53 is embedded and joined to the temporary fixing portion. As a result, the temporary fixing portion 53 is formed on the linear portion 52. Note that in the second end temporarily fixing step S18, the laser is not directly irradiated to the wire 50, but is irradiated to the third layer L3 of the second external electrode 42. Specifically, the laser is irradiated along the extending direction of the wire 50. As a result, the insulating coating 50B remains unmelted at the temporary fixing portion 53.

[0043] Next, a wire cutting step S19 is performed. As shown in Fig. 10, in the wire cutting step S19, first, the transparent member CP is removed from the wire 50. Next, a laser is irradiated to a portion of the wire 50 on the opposite side of the temporary fixing portion 53 from the portion wound around the winding core portion 11 in the extension direction of the wire 50. As a result, the wire 50 is cut, and a second end of the wire 50 is formed.

[0044] Next, the second end ball portion forming step S20 is performed. As shown in Fig. 11, in the second end ball portion forming step S20, a laser is irradiated to the second end of the wire 50. In the irradiated portion, the insulating coating 50B melts, exposing the conductor 50A. Then, in the irradiated portion, the conductor 50A melts to form a substantially spherical ball portion BP having a diameter larger than the wire diameter of the linear portion 52. In this state, some of the insulating coating 50B may remain on the surface.

[0045] Next, a second end pressing step S21 is performed. As shown in Fig. 12, in the second end pressing step S21, the ball portion BP is pressed against the second external electrode 42 using the transparent member CP. Specifically, the ball portion BP is sandwiched between the transparent member CP and the second external electrode 42. By pressing the transparent member CP against the ball portion BP, the insulating coating 50B remaining on the ball portion BP is welded to the transparent member CP.

[0046] Next, a second end joining step S22 is performed. As shown in FIG. 13, in the second end joining step S22, a laser is irradiated onto the ball part BP from the side of the transparent member CP in a state where the ball part BP is sandwiched between the transparent member CP and the second external electrode 42. Therefore, in this state, the ball part BP is in contact with the second external electrode 42. As a result, a second joint part 51B connected to the second external electrode 42 is formed at the second end of the wire 50. In addition, the ball part BP is embedded in the melted and softened third layer L3 by the pressing force of the transparent member CP, so that a buried portion 54 is formed. In addition, the end surface of the second joint part 51B in the first positive direction X1 is formed as a flat surface by the pressing force of the transparent member CP.

[0047] Next, a second end removing step S23 is performed. In the second end removing step S23, the transparent member CP is removed from the wire 50. That is, in the second end removing step S23, the insulating coating 50B remaining on the ball portion BP is removed from the wire 50 together with the transparent member CP.

[0048] <Effects of this embodiment> (1) In the above embodiment, the thickness of each joint 51 of wire 50 is greater than the thickness of linear portion 52. As a result, even if a certain amount of external force acts on each joint 51, wire 50 is less likely to break at the boundary between each joint 51 and linear portion 52.

[0049] (2) In the above embodiment, the first dimension A1 is larger than the wire diameter of the linear portion 52. This increases the contact area between each joint 51 and the external electrode 40. This prevents the wire 50 from coming off the external electrode 40.

[0050] (3) In the above embodiment, the second dimension A2 is smaller than the first dimension A1. Therefore, the buried portion 54 includes a portion having a shape whose dimension in the direction along the second axis Y becomes smaller toward the first positive direction X1 in the specific cross section. In other words, a part of the joint 51 is covered by the external electrode 40 from the outside. Therefore, the joint 51 is unlikely to come off the external electrode 40.

[0051] (4) In the above embodiment, the wire 50 has the conductor 50A and the insulating coating 50B. Each joint 51 has only the conductor 50A. With this configuration, the insulating coating 50B is less likely to impede the electrical connection between the joint 51 and the external electrode 40.

[0052] (5) In the above embodiment, the temporary fixing portion 53 has the conductor 50A and the insulating coating 50B. With this configuration, the conductor 50A in the temporary fixing portion 53 is not in direct contact with the external electrode 40. This prevents components of the conductor 50A from dissolving into the external electrode 40 and causing the conductor 50A to become thinner.

[0053] (6) In the above embodiment, the end of the bonding portion 51 on the first negative direction X2 side is located on the first positive direction X1 side with respect to the end of the second layer L2 on the first positive direction X1 side. That is, the bonding portion 51 does not reach the interface between the third layer L3 and the second layer L2. For example, if the bonding portion 51 reaches the interface between the third layer L3 and the second layer L2 in the second end pressing step S21, the bonding portion 51 may receive a reaction force from the interface. As a result, an excessive external force may be applied to the bonding portion 51. According to the above configuration, such an external force acting on the bonding portion 51 can be suppressed.

[0054] (7) In the above embodiment, the third layer L3 contains Sn. Sn is a relatively soft metal. Therefore, when connecting the joint 51 to the external electrode 40, the external force acting on the joint 51 can be suppressed.

[0055] (8) In the above embodiment, the linear portion 52 has a temporary fixing portion 53 joined to the third layer L3. The third layer L3 contains Sn. Therefore, the melting point of the third layer L3 is relatively low and it is easy to melt it by a laser or the like. As a result, in the second end temporary fixing step S18, the temporary fixing portion 53 can be formed by pressing the linear portion 52 against the molten third layer L3. By forming the temporary fixing portion 53, the wire 50 is less likely to become misaligned when the second joint portion 51B is formed.

[0056] (9) In the above embodiment, the end face of the joint portion 51 on the first positive direction X1 side is an end face parallel to the second axis Y and the central axis C. With this configuration, the posture of the coil component 10 is stabilized when the coil component 10 is connected to a substrate with solder or the like.

[0057] (10) In the above embodiment, the joining method of wire 50 includes a second end ball portion forming step S20 and a second end joining step S22. The joining method of wire 50 also includes a second end pressing step S21 after the second end ball portion forming step S20 and before the second end joining step S22. By performing the second end pressing step S21, the ball portion BP can be deeply embedded in the second external electrode 42. The same applies to the first end pressing step S13.

[0058] (11) In the above embodiment, the wire 50 has the conductor 50A and the insulating coating 50B at a stage before the second end ball portion forming step S20. The joining method of the wire 50 includes a second end removing step S23 of removing the transparent member CP together with the insulating coating 50B remaining on the ball portion BP from the wire 50 after the second end joining step S22. By performing the second end removing step S23, the conductor 50A is exposed on the end face of the second joint portion 51B on the first positive direction X1 side. Therefore, compared with a configuration in which the end face of the second joint portion 51B on the first positive direction X1 side includes the insulating coating 50B, the above configuration improves the wettability of the solder when the second external electrode 42 is connected to the board with solder or the like. The same applies to the first end removing step S15.

[0059] (12) In the above embodiment, in the first end pressing step S13 and the second end pressing step S21, the insulating coating 50B is welded only to a partial region of the transparent member CP. If the portion to which the insulating coating 50B is not welded is used, the same transparent member CP can be used again in the joining step of the wire 50. Therefore, the transparent member CP can be reused without being discarded after one use, and an increase in costs associated with the above steps can be suppressed.

[0060] (13) In the above embodiment, the third layer L3 of the external electrode 40 contains Sn. The conductor 50A contains Cu. That is, each joint 51 contains Cu. Therefore, a Cu-Sn alloy may be generated at the boundary between the joint 51 and the external electrode 40. If a Cu-Sn alloy is generated at the boundary in this manner, the electrical characteristics of the joint 51 are stable.

[0061] <Example of change> The above embodiment and the following modified examples can be implemented in combination with each other to the extent that no technical contradiction occurs.

[0062] There are no limitations on the configuration of the coil device 10. For example, the coil device 10 may be configured without the top plate 12. The winding core 11 does not have to be in the shape of a rectangular prism. For example, the cross-sectional shape of the winding core 11 may be a circle, an ellipse, or a polygon other than a rectangle.

[0063] The diameter of the linear portion 52 of the wire 50 is not limited to the example in the above embodiment. It is sufficient that the dimension P1 in the direction along the first axis X from the end of the joint 51 on the first negative direction X2 side to the end on the first positive direction X1 side is larger than the diameter of the linear portion 52.

[0064] The layer structure of the external electrode 40 is not limited to the example of the above embodiment. The external electrode 40 may have at least one conductive layer. In this case, the one layer constitutes the outermost layer. In the above embodiment, the material of each layer of the external electrode 40 is not limited to the example of the above embodiment.

[0065] The end of the joint 51 on the first negative direction X2 side may be located on the first negative direction X2 side with respect to the end of the second layer L2 on the first positive direction X1 side. In other words, the end of the joint 51 on the first negative direction X2 side may be located on the first negative direction X2 side with respect to the end of the inner layer on the first positive direction X1 side.

[0066] The joint 51 may have an insulating coating 50B in addition to the conductor 50A. It is sufficient that the joint 51 and the external electrode 40 are electrically connected. In the specific cross section, the first dimension A1 does not have to be the dimension of a location that is the maximum dimension of the buried portion 54 in the direction along the second axis Y. In the specific cross section, the dimension of the buried portion 54 in the direction along the second axis Y at any location in the direction along the first axis X may be the first dimension A1. In addition, when the dimension of the buried portion 54 in the direction along the second axis Y on the first positive direction X1 side from the location of the first dimension A1 is the second dimension A2, the effect of (3) can be obtained as long as the second dimension A2 is smaller than the first dimension A1.

[0067] The joint 51 does not have to be entirely embedded in the external electrode 40 as long as at least a part of it is embedded in the external electrode 40. For example, in the example shown in FIG. 14, in a specific cross section, the end of the joint 51 on the first negative direction X2 side is located on the first negative direction X2 side with respect to the end of the external electrode 40 on the first positive direction X1 side. On the other hand, in a specific cross section, the end of the joint 51 on the first positive direction X1 side is located on the first positive direction X1 side with respect to the end of the external electrode 40 on the first positive direction X1 side. In the example shown in FIG. 14 as well, the dimension P1 in the direction along the first axis X from the end of the joint 51 on the first positive direction X1 side to the end of the joint 51 on the first negative direction X2 side in the specific cross section is larger than the wire diameter of the linear portion 52. In the example shown in FIG. 14, the second dimension A2 is larger than the first dimension A1. 14, the maximum dimension of the buried portion 54 in the direction along the second axis Y is smaller than the wire diameter of the linear portion 52 in the specific cross section.

[0068] If the joint portion 51 is connected to the external electrode 40, the linear portion 52 does not need to have the temporarily fixed portion 53. In this case, in the method for joining the wire 50, the second end temporarily pressing step S17 and the second end temporarily fixing step S18 can be omitted.

[0069] In the method for joining the wire 50, it is possible to omit the first end pressing step S13, the first end removing step S15, the second end pressing step S21, and the second end removing step S23. In other words, if the joint portion 51 is connected to the external electrode 40, it is not necessary to use the transparent member CP in the method for joining the wire 50.

[0070] The method for manufacturing the coil component is not limited to the above embodiment. For example, the preparation step S11 may be followed by the winding step S16, followed by the first end ball portion forming step S12 and the first end joining step S14.

[0071] <Additional Notes> The technical ideas that can be derived from the above-described embodiments and modifications will be described below. [1] A core having a columnar winding core and a pair of flanges connected to ends of the winding core in a direction along the central axis, a wire wound around the winding core, and an external electrode covering an outer surface of the flange, wherein a specific axis perpendicular to the central axis is defined as a first axis, one of the directions along the first axis is defined as a positive direction, and a direction opposite to the positive direction is defined as a negative direction, the flange protrudes toward the positive direction relative to the outer surface of the winding core, and the external electrode is disposed on the outer surface of the flange facing the positive direction. a coil component having a surface covering the wire, the wire having a linear portion wound around the winding core portion and a joint portion located at an end of the wire and connected to the external electrode, wherein in a cross section perpendicular to the central axis and including the joint portion, the negative end of the joint portion is located on the negative side of the positive end of the external electrode, and the dimension along the first axis from the negative end to the positive end of the joint portion is larger than a wire diameter of the linear portion.

[0072] [2] A coil component as described in [1], wherein when an axis perpendicular to both the central axis and the first axis is defined as a second axis, and when, in the cross section, a portion of the joint that is located on the negative side of the end of the external electrode on the positive side is defined as a buried portion, in the cross section, the maximum dimension of the buried portion in a direction along the second axis is larger than the wire diameter of the linear portion.

[0073] [3] A coil component according to [1] or [2], wherein an axis perpendicular to both the central axis and the first axis is defined as a second axis, a portion of the joint that is located on the negative side of the end of the external electrode on the positive side in the cross section is defined as a buried portion, a dimension of the buried portion in a direction along the second axis at any point in the cross section in a direction along the first axis is defined as a first dimension, and a dimension of the buried portion in a direction along the second axis on the positive side with respect to a point at the first dimension is defined as a second dimension, wherein the second dimension is smaller than the first dimension.

[0074] [4] The coil component according to any one of [1] to [3], wherein the wire has a linear conductor and an insulating coating covering an outer surface of the conductor, the linear portion has the insulating coating and the conductor, and the joint portion has only the conductor.

[0075] [5] The coil component according to any one of [1] to [4], wherein the external electrode has an inner layer and an outer layer located on the opposite side of the inner layer from the outer surface of the flange portion, and in the cross section, the negative end of the joint is located on the positive side of the positive end of the inner layer.

[0076] [6] The coil component according to any one of [1] to [5], wherein the external electrodes have an outermost layer that is the outermost layer of the external electrodes, and the outermost layer contains Sn. [7] The coil component according to [6], wherein the linear portion has a temporary fixing portion joined to the outermost layer.

[0077] [8] A method for joining a wire, comprising: a ball portion forming step of melting the wire to form a ball portion at an end of the wire, the ball portion having a diameter larger than the wire diameter of the linear portion before melting; and a joining step of irradiating the ball portion with a laser while the ball portion is in contact with an external electrode covering the outer surface of a core, to form a joint at the end of the wire, the joint being connected to the external electrode.

[0078] [9] The wire joining method described in [8], further comprising a pressing step, which, after the ball portion forming step and before the joining step, sandwiches the ball portion between a transparent member made of a material through which the laser passes and the external electrode, thereby pressing the ball portion against the external electrode, and in the joining step, irradiates the laser from the side of the transparent member while the ball portion is sandwiched between the transparent member and the external electrode.

[0079]

[10] The wire joining method described in [9], wherein the wire has a linear conductor and an insulating coating covering an outer surface of the conductor prior to the ball portion forming process, and the joining process includes a removal process of removing the transparent member from the wire together with the insulating coating remaining in the ball portion.

[0080]

[11] A method for manufacturing a coil component, comprising: a preparation step of preparing a core having a columnar winding core portion and a pair of flange portions connected to ends of the winding core portion in a direction along the central axis, the core being provided with an external electrode covering the outer surface of the flange portions; a winding step of winding a wire around the winding core portion; a ball portion forming step of melting the wire to form a ball portion at an end of the wire having a diameter larger than the wire diameter of the linear portion before melting; and a joining step of irradiating the ball portion with a laser while the ball portion is in contact with the external electrode to form a joint at the end of the wire connected to the external electrode.

[0081]

[12] A method for manufacturing a coil component as described in

[11] , further comprising, after the ball portion forming process and before the joining process, a pressing process in which the ball portion is pressed against the external electrode by sandwiching the ball portion between a transparent member made of a material through which the laser passes and the external electrode, and in the joining process, the laser is irradiated from the side of the transparent member while the ball portion is sandwiched between the transparent member and the external electrode.

[0082]

[13] The method for manufacturing a coil component described in

[12] , wherein the wire has a linear conductor and an insulating coating covering an outer surface of the conductor at a stage prior to the ball portion forming process, and the method includes a removal process of removing the transparent member from the wire together with the insulating coating remaining in the ball portion after the joining process.

[0083]

[14] The method for manufacturing a coil component described in any one of

[11] to

[13] , wherein the external electrode has an outermost layer which is the outermost layer of the external electrode and contains Sn, and the method includes a temporary fixing process, prior to the ball portion forming process, of irradiating a temporary fixing point of the external electrode with the laser to join the temporary fixing point on the winding core portion side to a point in the wire where the joint is to be formed. [Explanation of symbols]

[0084] A1…First dimension A2…Second dimension BP: Ball section C…Central axis CP: Transparent material P1…Dimensions X…1st axis X1…first positive direction X2…1st negative direction 10...Coil parts 10C…Core 11...Core 20…Flange 40…External electrode 50…Wire 50A…Conductor 50B…insulating coating 51…Joint part 52...Linear part 53…Temporary fixing part 54...Buried part

Claims

1. A core having a columnar winding core portion and a pair of flange portions connected to ends of the winding core portion in a direction along a central axis thereof; A wire wound around the winding core; an external electrode covering an outer surface of the flange; Equipped with When a specific axis perpendicular to the central axis is defined as a first axis, one direction along the first axis is defined as a positive direction, and the direction opposite to the positive direction is defined as a negative direction, The flange portion protrudes toward the positive direction from an outer surface of the winding core portion, the external electrode covers a surface of the flange portion that faces the positive direction, the wire has a linear portion wound around the winding core and a joint portion located at an end of the wire and connected to the external electrode, In a cross section perpendicular to the central axis and including the joint, the negative end of the joint is located on the negative side of the positive end of the external electrode, and a dimension along the first axis from the negative end to the positive end of the joint is larger than a wire diameter of the linear portion. Coil parts.

2. An axis perpendicular to both the central axis and the first axis is defined as a second axis, When a portion of the joint that is located on the negative side of the end of the external electrode on the positive side in the cross section is defined as a buried portion, In the cross section, the maximum dimension of the buried portion in the direction along the second axis is larger than the wire diameter of the linear portion. The coil component according to claim 1 .

3. An axis perpendicular to both the central axis and the first axis is defined as a second axis, a buried portion is a portion of the joint portion that is located on the negative side of the end of the external electrode on the positive side in the cross section, In the cross section, a dimension of the buried portion in a direction along the second axis at any point in a direction along the first axis is defined as a first dimension, and a dimension of the buried portion in a direction along the second axis on the positive side of the point at the first dimension is defined as a second dimension. The second dimension is smaller than the first dimension. The coil component according to claim 1 .

4. The wire has a linear conductor and an insulating coating covering an outer circumferential surface of the conductor, the linear portion has the insulating coating and the conductor, The joint portion includes only the conductor. The coil component according to claim 1 .

5. the external electrode has an inner layer and an outer layer located on the opposite side of the inner layer from the outer surface of the flange portion, In the cross section, the negative end of the joint is located on the positive side of the positive end of the inner layer. The coil component according to claim 1 .

6. the external electrode has an outermost layer that is an outermost layer of the external electrode, The outermost layer contains Sn. The coil component according to claim 1 .

7. The linear portion has a temporary fixing portion joined to the outermost layer. The coil component according to claim 6.

8. a ball portion forming step of melting the wire to form a ball portion at an end of the wire, the ball portion having a diameter larger than the diameter of the wire portion before melting; a joining step of irradiating a laser beam to the ball portion in a state in which the ball portion is in contact with an external electrode covering an outer surface of a core, thereby forming a joint portion at an end of the wire that is connected to the external electrode; have How wires are joined.

9. After the ball portion forming step and before the joining step, a pressing step of pressing the ball portion against the external electrode by sandwiching the ball portion between a transparent member made of a material through which the laser transmits and the external electrode, In the joining step, the ball portion is sandwiched between the transparent member and the external electrode, and the laser is irradiated from the transparent member side. The method for bonding wires according to claim 8.

10. the wire has a linear conductor and an insulating coating covering an outer circumferential surface of the conductor at a stage prior to the ball portion forming step, After the bonding step, a removing step is performed to remove the transparent member from the wire together with the insulating coating remaining on the ball portion. The method for bonding wires according to claim 9.

11. a preparation step of preparing a core having a columnar winding core portion and a pair of flange portions connected to ends of the winding core portion in a direction along a central axis thereof, the core being provided with an external electrode covering an outer surface of the flange portions; a winding step of winding a wire around the winding core; a ball portion forming step of melting the wire to form a ball portion at an end of the wire, the ball portion having a diameter larger than a diameter of the wire portion before melting; a bonding process for forming a bonding portion at an end of the wire, the bonding portion being connected to the external electrode, by irradiating the ball portion with a laser while the ball portion is in contact with the external electrode; have A manufacturing method for coil components.

12. After the ball portion forming step and before the joining step, a pressing step of pressing the ball portion against the external electrode by sandwiching the ball portion between a transparent member made of a material through which the laser transmits and the external electrode, In the joining step, the ball portion is sandwiched between the transparent member and the external electrode, and the laser is irradiated from the transparent member side. The method for manufacturing the coil component according to claim 11 .

13. the wire has a linear conductor and an insulating coating covering an outer circumferential surface of the conductor at a stage prior to the ball portion forming step, After the bonding step, a removing step is performed to remove the transparent member from the wire together with the insulating coating remaining on the ball portion. The method for manufacturing a coil component according to claim 12.

14. the external electrode has an outermost layer which is the outermost layer of the external electrode and contains Sn, The method includes a temporary fixing step of irradiating a temporary fixing portion of the external electrode with the laser before the ball portion forming step, and joining a temporary fixing portion on the winding core portion side to the temporary fixing portion at a location where the joint portion of the wire is to be formed. The method for manufacturing the coil component according to claim 11 .

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