Coil component and core component for coil component
Patent Information
- Application Number
- PCT/JP2025/007617
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2024-03-07
- Filing Date
- 2025-03-04
- Publication Date
- 2025-10-02
AI Technical Summary
In existing coil components, the thermocompression bonding process leads to the thermal decomposition of the wire coating, causing the plating layer to be pushed aside and resulting in locally thin portions of the external electrode, which affects the bonding strength and wettability during mounting.
The design incorporates a cylindrical winding core with flanges featuring recesses and protrusions on the external electrodes, allowing steam generated during thermocompression bonding to escape through these recesses, preventing excessive thinning and maintaining bonding strength by reflecting the shape of the core recesses and protrusions in the external electrode.
Prevents excessive thinning of the external electrodes, enhances bonding strength, and reduces the likelihood of decreased wettability by providing an escape route for steam, thus improving the reliability and performance of the coil component.
Smart Images
Figure JP2025007617_02102025_PF_FP_ABST
Abstract
Description
Coil components and core components for coil components
[0001] The present disclosure relates to coil components and core components for coil components.
[0002] The coil component described in Patent Document 1 includes a winding core and two flanges. The winding core is rectangular prism-shaped. The two flanges are connected to both ends of the winding core. The winding core and flanges form the core of the coil component. The coil component described in Patent Document 1 also includes an electrode and a wire. The electrode is attached to the flange. The electrode has a base electrode and a plating layer. The wire is wound around the winding core. The wire has a conductor and a coating that covers the conductor. The end of the wire is attached to the electrode by thermocompression bonding.
[0003] Japanese Patent Application Laid-Open No. 2017-162897
[0004] In a coil component such as that described in Patent Document 1, when the wire end is thermocompression bonded, a jig such as a heater tip is pressed against the wire end. When the jig is pressed against the wire end, the wire coating is thermally decomposed into vapor. The vapor flows outward from between the jig and the electrode, pushing aside the molten plating layer. When the plating layer is pushed aside by the vapor, the pushed-aside portion remains as a thin portion of the plating layer.
[0005] In order to solve the above problems, the present disclosure provides a coil component comprising: a cylindrical winding core having a columnar winding core and a pair of flanges connected to the winding core in a direction along the central axis of the winding core; an external electrode covering the outer surface of the flange; and a wire wound around the winding core and joined to the external electrode, 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 the direction opposite to the positive direction is defined as a negative direction, the external electrode covers the surface of the outer surface of the flange facing the positive direction, and the external electrode has a recess that is recessed in the negative direction, and when the portion of the wire joined to the external electrode is defined as a joint, the joint is a coil component that straddles the recess.
[0006] Furthermore, in order to solve the above-described problems, the present disclosure provides a core for a coil component, comprising: a drum-shaped core having a columnar winding core and a pair of flanges connected to the winding core in a direction along the central axis of the winding core; and an external electrode covering the 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 the direction opposite to the positive direction is defined as a negative direction, the external electrode covers the surface of the outer surface of the flange facing the positive direction, and the external electrode has a recess that is recessed in the negative direction, and when viewed facing the negative direction, the recess is a core component for a coil component that extends linearly.
[0007] According to the above configuration, it is possible to prevent the external electrodes from becoming locally thin.
[0008] FIG. 1 is a perspective view of a coil component according to a first embodiment. FIG. 2 is a plan view showing the periphery of an external electrode of the coil component according to the first embodiment. FIG. 3 is a schematic end view showing a part of a cross section taken along line 3-3 in FIG. 2. FIG. 4 is a plan view showing the periphery of an external electrode of a coil component according to a second embodiment. FIG. 5 is a schematic end view showing a part of a cross section taken along line 5-5 in FIG. 4. FIG. 6 is a plan view showing the periphery of an external electrode of a coil component according to a modified example. FIG. 7 is a schematic end view showing a part of a cross section taken along line 7-7 in FIG. 6. FIG. 8 is a plan view showing the periphery of an external electrode of a coil component according to a modified example.
[0009] Hereinafter, first and second embodiments of a coil component including a core component will be described with reference to the drawings. Note that the drawings may show components enlarged to facilitate understanding. The dimensional ratios of the components may differ from those in the actual drawings or from those in other drawings.
[0010] First Embodiment <Overall Configuration> As shown in FIG. 1, a coil device 10 includes a drum-shaped core 10C.
[0011] The drum-shaped core 10C includes a columnar winding core 11, a first flange 21, and a second flange 22. That is, the drum-shaped core 10C has a pair of flanges 20. The winding core 11 is in the shape of a quadrangular pillar. The material of the winding core 11 is, for example, alumina, Ni-Zn ferrite, synthetic resin, or a mixture thereof.
[0012] The first flange 21 is connected to a first end of the winding core 11 in a direction along the central axis X. The second flange 22 is connected to a second end of the winding core 11 in a direction along the central axis X. The first flange 21 and the second flange 22 are made of the same material as the winding core 11. The first flange 21 and the second flange 22 are integrally molded with the winding core 11.
[0013] Here, a specific axis perpendicular to the central axis X of the winding core 11 is referred to as the first axis Y. In this embodiment, the first axis Y is parallel to two of the four sides of the winding core 11 when viewed in the direction along the central axis X. An axis perpendicular to both the central axis X and the first axis Y is referred to as the second axis Z. In this embodiment, the second axis Z is parallel to the remaining two of the four sides of the winding core 11 when viewed in the direction along the central axis X. One of the directions along the central axis X is referred to as the positive direction X1, and the direction opposite to the positive direction X1 is referred to as the negative direction X2. In this embodiment, the positive direction X1 coincides with the direction along the central axis X from the winding core 11 toward the first flange 21. The negative direction X2 coincides with the direction along the central axis X from the winding core 11 toward the second flange 22. One of the directions along the first axis Y is defined as a first positive direction Y1, and the direction opposite to the first positive direction Y1 is defined as a first negative direction Y2. Similarly, one of the directions along the second axis Z is defined as a second positive direction Z1, and the direction opposite to the second positive direction Z1 is defined as a second negative direction Z2.
[0014] When viewed from the direction along the central axis X, the first flange portion 21 protrudes outward relative to the winding core portion 11 in the directions along the first axis Y and the second axis Z. The first flange portion 21 has a shape that is plane-symmetrical with respect to an imaginary plane that passes through the central axis X and is parallel to the central axis X. The first flange portion 21 also has a flat shape in which the dimension along the central axis X is smaller than the dimension along the first axis Y and the dimension along the second axis Z.
[0015] The second flange 22 and the first flange 21 have shapes that are plane-symmetrical with respect to an imaginary plane that passes through the center of the winding core 11 and is parallel to the second axis Z and the first axis Y. That is, when viewed from the direction along the central axis X, the second flange 22 protrudes outward relative to the winding core 11 in the direction along the first axis Y and the direction along the second axis Z. In the following description, when there is no need to distinguish between the first flange 21 and the second flange 22, they will be referred to as flange 20.
[0016] The coil device 10 includes two external electrodes 40. One external electrode 40 covers the entire surface of the first flange 21 facing in the first positive direction Y1 and a portion of the surface adjacent to the surface facing in the first positive direction Y1. The other external electrode 40 covers the entire surface of the second flange 22 facing in the first positive direction Y1 and a portion of the surface adjacent to the surface facing in the first positive direction Y1. The drum-shaped core 10C and the external electrode 40 form a core component of the coil device 10.
[0017] As shown in FIG. 3 , the external electrode 40 includes a base electrode layer 41 and a plating layer 42. The base electrode layer 41 is in contact with the outer surface of the flange 20 facing the first positive direction Y1. That is, the base electrode layer 41 directly covers the outer surface of the flange 20 facing the first positive direction Y1. The base electrode layer 41 is made of a material mainly composed of silver. The plating layer 42 is laminated on the base electrode layer 41 on the first positive direction Y1 side. Although not shown, the plating layer 42 is laminated in this order from the base electrode layer 41 side to the first positive direction Y1 side. Note that the end surface of the coil component 10 facing the first positive direction Y1, on which each external electrode 40 is located, is the mounting surface that faces the substrate when the coil component 10 is mounted on the substrate.
[0018] As shown in Fig. 1, the coil device 10 includes a wire 70 wound around a winding core 11. Although not shown, the wire 70 includes a conductor and an insulating coating. The insulating coating covers the outer surface of the conductor. When viewed in cross section perpendicular to the direction in which the wire 70 extends, the shape of the wire 70 is substantially circular.
[0019] A first end of the wire 70 is joined by thermocompression to the external electrode 40 on the first flange 21 side. A second end of the wire 70 is joined by thermocompression to the external electrode 40 on the second flange 22 side. When viewed in the negative direction X2, the wire 70 is wound around the winding core 11 so as to progress counterclockwise from the first end to the second end.
[0020] 2, each flange 20 has a plurality of core recesses 31 and a plurality of core protrusions 32. Each flange 20 has three core recesses 31 and four core protrusions 32. Each core recess 31 and each core protrusion 32 is present on the surface of the flange 20 on the first positive direction Y1 side.
[0021] As shown in Fig. 3, each core recess 31 is a portion recessed toward the first negative direction Y2 on the surface of the flange portion 20 on the first positive direction Y1 side. As shown in Fig. 2, when viewed in the first negative direction Y2, each core recess 31 extends linearly in a direction along the second axis Z. The multiple core recesses 31 extend parallel to one another at equal intervals. Note that "extending linearly" here means that the center line of each core recess 31 is linear.
[0022] The center line is determined as follows: Among the line segments that can be drawn from any point on the edge of the core recess 31 on the first positive direction Y1 side to the edge on the opposite side, the shortest line segment is identified. The line connecting the points that pass through the centers of the identified line segments is defined as the center line of the core recess 31.
[0023] Each core recess 31 extends from the surface of each flange 20 facing the first positive direction Y1 to the edge on the second positive direction Z1 side and the edge on the second negative direction Z2 side. That is, each core recess 31 is open in the flange 20 in the direction along the second axis Z.
[0024] The core protrusions 32 are portions of the flange 20 that protrude in the first positive direction Y1. Each core protrusion 32 is located adjacent to a core recess 31 in the direction along the central axis X. Therefore, two of the four core protrusions 32 are located between the core recesses 31 in the direction along the central axis X. The remaining two core protrusions 32 are located at the end of the flange 20 on the positive direction X1 side and the end on the negative direction X2 side, respectively. As a result, the surface of each flange 20 facing the first positive direction Y1 has an uneven shape.
[0025] The boundary between the core recess 31 and the core protrusion 32 is defined as follows. As shown in FIG. 3 , the flange 20 is viewed end-on in a cross section perpendicular to the extension direction of the core recess 31. Then, for adjacent core protrusions 32 and core recesses 31, the midpoints of lines parallel to the first axis Y that pass through the tip of the core protrusion 32 on the first positive direction Y1 side and the bottom of the core recess 31 on the first negative direction Y2 side are identified. Such midpoints are identified for each of the adjacent core protrusions 32 and core recesses 31. A first approximate straight line AS1 is then drawn to each of the identified midpoints. The portion of the flange 20 located on the first positive direction Y1 side with respect to the first approximate straight line AS1 is the core protrusion 32. Furthermore, the portion of the first flange 21 located on the first negative direction Y2 side with respect to the first approximate straight line AS1 is the core recess 31.
[0026] 2 , each external electrode 40 has a plurality of recesses 51 and a plurality of protrusions 52. The base electrode layer 41 and the plating layer 42 of the external electrode 40 have an uneven shape that reflects the shapes of the core recesses 31 and the core protrusions 32.
[0027] Specifically, each external electrode 40 has three recesses 51 and four protrusions 52. As shown in Fig. 3 , each recess 51 is a portion of the external electrode 40 that is recessed in the first negative direction Y2. The recess 51 is a portion of the external electrode 40 that covers the core recess 31. As described above, in each external electrode 40, the base electrode layer 41 and the plating layer 42 have an uneven shape. Therefore, the recess 51 is also a portion of the plating layer 42 that covers the recess shape of the base electrode layer 41.
[0028] Each protrusion 52 is a portion of the external electrode 40 that protrudes in the first positive direction Y1. As shown in Fig. 2 , two of the protrusions 52 are located between adjacent recesses 51 that extend parallel to each other. Furthermore, as shown in Fig. 3 , the protrusions 52 are portions that cover the core protrusions 32.
[0029] 2, when viewed in the first negative direction Y2, each recess 51 extends linearly in a direction along the second axis Z. The recesses 51 extend parallel to one another at equal intervals. Note that "extending linearly" has the same definition as described above.
[0030] Each recess 51 extends to an edge on the second positive direction Z1 side and an edge on the second negative direction Z2 side on the surface of the external electrode 40 facing the first positive direction Y1. That is, each recess 51 opens in the direction along the second axis Z in the external electrode 40.
[0031] The protrusions 52 are portions of the external electrode 40 that protrude in the first positive direction Y1. Each protrusion 52 is located adjacent to a recess 51 in the direction along the central axis X. Therefore, two of the four protrusions 52 are located between adjacent recesses 51 in the direction along the central axis X. The remaining two protrusions 52 are located at the end of the external electrode 40 on the positive direction X1 side and the end on the negative direction X2 side, respectively. As a result, the surface of each external electrode 40 facing the first positive direction Y1 has an uneven shape. Note that the boundary between the protrusions 52 and recesses 51 in the external electrode 40 can be determined in the same manner as the boundary between the core recess 31 and core protrusion 32 described above. That is, as shown in FIG. 3 , the midpoint positions of adjacent protrusions 52 and recesses 51 are identified. Then, a second approximate straight line AS2 is drawn for each identified midpoint. The portion of the external electrode 40 located on the first positive direction Y1 side with respect to the second approximate straight line AS2 is the convex portion 52. The portion of the external electrode 40 located on the first negative direction Y2 side with respect to the second approximate straight line AS2 is the concave portion 51.
[0032] Here, the specific direction is defined as a direction perpendicular to the first axis Y and the extension direction of the recesses 51. In this embodiment, the specific direction coincides with the direction along the central axis X. As shown in FIG. 2 , the dimension H1 in the specific direction of the three recesses 51 is the same. In addition, the dimension H2 in the specific direction of the two protrusions 52 located between adjacent recesses 51 is the same.
[0033] 3, the dimension H2 in the specific direction of the protrusion 52 located between adjacent recesses 51 is larger than the dimension H1 in the specific direction of the recess 51. In other words, the ratio of the dimension H2 in the specific direction of the protrusion 52 to the sum of the dimension H1 in the specific direction of the recess 51 and the dimension H2 in the specific direction of the protrusion 52 is 50% or more.
[0034] Furthermore, between adjacent convex portions 52 and concave portions 51, the maximum dimension T1 in the direction along the first axis Y from the tip of the convex portion 52 to the bottom of the concave portion 51 is 10 μm or more. If the maximum dimension T1 can be measured at multiple locations of the concave portions 51 and the convex portions 52, the maximum dimension T1 is measured at three or more locations, and if the average value of the maximum dimensions T1 is 10 μm or more, it is determined that the "maximum dimension T1 is 10 μm."
[0035] <Joining Between Recess and Wire in First Embodiment> As shown in FIG. 2, a portion of the wire 70 that is joined to the external electrode 40 is referred to as a joining portion EP.
[0036] The joint EP is compressed by thermocompression bonding, reducing its thickness in the direction along the first axis Y. In this embodiment, the joint EP overlaps with the external electrode 40 when viewed in the first negative direction Y2. The dimension of the joint EP in the direction along the first axis Y is approximately 10 μm. When viewed in the first negative direction Y2, the joint EP has a generally elliptical shape as a whole. The tip of the joint EP faces obliquely toward the second positive direction Z1 and the positive direction X1.
[0037] The joint EP straddles two recesses 51 and three protrusions 52. The tip of the joint EP on the positive direction X1 side overlaps the recess 51. Assume that the external electrode 40 is viewed in cross section along a cross section including two opposing edges of the recess 51. In this case, if the joint EP extends continuously from one edge of the recess 51 to the other edge, it is considered that "the joint EP straddles the recess 51." Furthermore, the portion of the joint EP facing the recess 51 may not be in direct contact with the external electrode 40. Even in this case, the portion of the wire 70 facing the external electrode 40 in the direction along the first axis Y is still considered to be the joint EP.
[0038] As described above, since the joint EP spans multiple recesses 51, the dimension H1 in the specific direction of the recess 51 is smaller than the dimension H3 in the specific direction of the joint EP. In this embodiment, the dimension H3 in the specific direction of the joint EP is the dimension along the central axis X from the point of the joint EP closest to the positive direction X1 to the point of the joint EP closest to the negative direction X2.
[0039] Here, when viewed in the first negative direction Y2, an imaginary line V is drawn along the central axis X, passing through the point of the joint EP farthest from the winding core 11 and the point of the joint EP closest to the winding core 11. In this embodiment, the point of the joint EP closest to the winding core 11 is a linear point of the joint EP that overlaps with the edge of the external electrode 40 on the negative direction X2 side. In this case, the midpoint of this linear point is defined as the point of the joint EP closest to the winding core 11. The acute angle α formed by the imaginary line V and the second axis Z is approximately 45 degrees. In other words, the acute angle α formed by the imaginary line V and the extension direction of the recess 51 is greater than or equal to 40 degrees and less than 90 degrees.
[0040] <Operation of the First Embodiment> When joining the wire 70 to the external electrode 40, a heater tip is pressed against the wire 70 on the external electrode 40. Then, the heater tip is pressed at a preset temperature for a preset time. This crushes the end of the wire 70, forming a joint EP joined to the external electrode 40. In this process of forming the joint EP, the insulating coating in the part of the wire 70 that is in contact with the heater tip is thermally decomposed and turns into steam.
[0041] <Effects of the First Embodiment> (1-1) According to the first embodiment, steam generated when the wire 70 is thermocompression bonded to the external electrode 40 can flow from between the heater tip and the external electrode 40 to the outside via the recess 51. In other words, the recess 51 serves as an escape route for the steam. Therefore, the configuration of the first embodiment can prevent the external electrode 40 from being excessively pushed aside by the steam generated during thermocompression bonding. As a result, it can prevent a portion of the external electrode 40 from becoming excessively thinner than the designed thickness.
[0042] Furthermore, when heated, the residue of the insulating coating that does not evaporate but remains unmelted is likely to drip into the recess 51. Therefore, compared to when the residue of the insulating coating remains on the first positive direction Y1 side of the external electrode 40, the wettability of the solder is less likely to decrease when the coil component 10 is mounted.
[0043] (1-2) In the first embodiment, when viewed in the first negative direction Y2, each recess 51 extends linearly. With this configuration, steam generated during thermocompression bonding tends to flow along the extension direction of the recess 51. As a result, with the above configuration, steam is less likely to stagnate within the recess 51.
[0044] (1-3) In the first embodiment, each recess 51 extends in a direction along the second axis Z. This configuration makes it easier for steam generated during thermocompression bonding to escape in a direction along the second axis Z. By allowing the steam to escape in this way in a direction along the second axis Z, the steam is less likely to hit the winding core 11, the portion of the wire 70 wound around the winding core 11, and the like.
[0045] (1-4) In the first embodiment, when viewed in the first negative direction Y2, the acute angle α formed by the imaginary line V and the extension direction of the recess 51 is greater than or equal to 40 degrees and less than 90 degrees. The imaginary line V can be said to be the extension direction of the joint EP on the external electrode 40. The smaller the acute angle α formed by this imaginary line V and the extension direction of the recess 51, the longer the length of the imaginary line V that exists within the range of the recess 51. Accordingly, the surface area of the portion of the joint EP exposed inside the recess 51 also increases, making it easier for steam generated during thermocompression bonding to reach the recess 51. On the other hand, as the acute angle α formed by the imaginary line V and the extension direction of the recess 51 approaches zero, the area of the joint EP that contacts the protrusion 52 of the external electrode 40 decreases, thereby reducing the bonding strength of the wire 70 to the external electrode 40. By setting the angle to the acute angle α as described above, the bonding strength of the wire 70 can be maintained at a required strength, while the recess 51 can effectively function as an escape route for steam.
[0046] (1-5) In the first embodiment, the dimension H1 of the recess 51 in the specific direction is smaller than the dimension H3 of the joint EP in the specific direction. With this configuration, the joint EP spans the entire recess 51 in the specific direction, regardless of the direction in which the joint EP extends.
[0047] (1-6) In the first embodiment, the ratio of the dimension H2 in the specific direction of the protrusion 52 to the sum of the dimension H1 in the specific direction of the recess 51 and the dimension H2 in the specific direction of the protrusion 52 is 50% or more. The larger this ratio, the more likely it is that the portion of the joint EP will come into contact with the external electrode 40. Therefore, with the above configuration, the bonding strength of the wire 70 to the external electrode 40 is less likely to decrease.
[0048] (1-7) In the first embodiment, the maximum dimension T1 from the tip of the convex portion 52 to the bottom of the concave portion 51 in the direction along the first axis Y is 10 μm or more. The dimension of the joint portion EP in the direction along the first axis Y is approximately 10 μm. Therefore, according to this dimensional relationship, the joint portion EP is unlikely to come into contact with the bottom of the concave portion 51. In other words, the above configuration can prevent the joint portion EP from blocking the concave portion 51.
[0049] (1-8) In the first embodiment, the flange portion 20 has a core recess 31 recessed in the first negative direction Y2. The recess 51 covers the core recess 31. According to this configuration, the recess 51 in the external electrode 40 is formed to reflect the shape of the core recess 31. In other words, the recess 51 can be formed without special processing of the external electrode 40. Therefore, the processing process of the coil component 10 is not likely to become complicated.
[0050] Second Embodiment A coil component according to a second embodiment will be described below. The configuration of the winding core 11 and the wire 70 wound around the winding core 11 in the coil component 10 of the second embodiment is the same as that of the first embodiment. The following describes the configuration around the external electrode 40, which is different from that of the first embodiment.
[0051] <Regarding Concave and Convex Portions in Second Embodiment> As shown in Fig. 4 , each external electrode 40 has a plurality of concave portions 51 and a plurality of convex portions 52. Furthermore, as shown in Fig. 5 , in the second embodiment, the surface of each flange portion 20 facing the first positive direction Y1 is flat. That is, the base electrode layer 41 of each external electrode 40 is in contact with a flat portion of the outer surface of the flange portion 20. Furthermore, the plating layer 42 is laminated on the base electrode layer 41 on the side of the first positive direction Y1.
[0052] As shown in FIG. 4 , the base electrode layer 41 has seven electrode recesses 61 and eight electrode protrusions 62. Each electrode recess 61 is a portion of the base electrode layer 41 that is recessed in the first negative direction Y2. As shown in FIG. 5 , when the base electrode layer 41 is viewed from an end, the corners of the electrode recesses 61 are curved. As shown in FIG. 4 , when viewed in the first negative direction Y2, each electrode recess 61 extends linearly in a direction along the central axis X. Furthermore, the multiple electrode recesses 61 extend parallel to one another at equal intervals. Note that the definition of "extending linearly" is the same as in the first embodiment.
[0053] Each electrode recess 61 extends to an edge on the positive direction X1 side and an edge on the negative direction X2 side on the surface of each base electrode layer 41 facing the first positive direction Y1. That is, each electrode recess 61 opens in the direction along the central axis X in the base electrode layer 41.
[0054] The electrode protrusions 62 are portions of the base electrode layer 41 that protrude in the first positive direction Y1. As shown in FIG. 5 , when the base electrode layer 41 is viewed from an end, the corners of the electrode protrusions 62 are curved. As shown in FIG. 4 , each electrode protrusion 62 is located adjacent to an electrode recess 61 in the direction along the second axis Z. Therefore, six of the eight core protrusions 32 are located between adjacent electrode recesses 61 in the direction along the second axis Z. The remaining two electrode protrusions 62 are located at the end of the base electrode layer 41 on the second positive direction Z1 side and the end on the second negative direction Z2 side, respectively. As a result, the surface of each base electrode layer 41 facing the first positive direction Y1 has an uneven shape. Note that the boundaries between the electrode recesses 61 and the electrode protrusions 62 are determined in the same manner as in the first embodiment.
[0055] 5 , each external electrode 40 has a plurality of recesses 51 and a plurality of protrusions 52. The plating layer 42 of the external electrode 40 has an uneven shape that reflects the shapes of the electrode recesses 61 and the electrode protrusions 62. Therefore, the portions of the plating layer 42 that cover the electrode recesses 61 are the recesses 51 of the external electrode 40, and the portions of the plating layer 42 that cover the electrode protrusions 62 are the protrusions 52 of the external electrode 40.
[0056] 4 , each external electrode 40 has seven recesses 51 and eight protrusions 52. Each recess 51 is a portion of the external electrode 40 that is recessed in the first negative direction Y2. Each protrusion 52 is a portion of the external electrode 40 that protrudes in the first positive direction Y1. Six of the protrusions 52 are located between adjacent recesses 51 that extend parallel to each other.
[0057] When viewed in the first negative direction Y2, each recess 51 extends linearly in a direction along the central axis X. The recesses 51 extend parallel to one another at equal intervals. Note that "extending linearly" has the same definition as described above.
[0058] Each recess 51 extends to an edge on the positive direction X1 side and an edge on the negative direction X2 side on the surface of the external electrode 40 facing the first positive direction Y1. That is, each recess 51 is open in the direction along the central axis X of the external electrode 40.
[0059] The protrusions 52 are portions of the external electrode 40 that protrude in the first positive direction Y1. Each protrusion 52 is located adjacent to a recess 51 in the direction along the second axis Z. Therefore, six of the eight protrusions 52 are located between adjacent recesses 51 in the direction along the second axis Z. The remaining two protrusions 52 are located at the end of the external electrode 40 on the second positive direction Z1 side and the end on the second negative direction Z2 side, respectively. As a result, the surface of each external electrode 40 facing the first positive direction Y1 has an uneven shape. Note that the boundary between the protrusions 52 and recesses 51 in the external electrode 40 can be determined in the same manner as the boundary between the core recess 31 and core protrusion 32 described in the first embodiment. That is, as shown in FIG. 5 , the midpoint positions of adjacent protrusions 52 and recesses 51 are identified. Then, a third approximate line AS3 is drawn for each identified midpoint. The portion of the external electrode 40 located on the first positive direction Y1 side with respect to the third approximate straight line AS3 is the convex portion 52. The portion of the external electrode 40 located on the first negative direction Y2 side with respect to the third approximate straight line AS3 is the concave portion 51.
[0060] Here, the specific direction is defined as a direction perpendicular to the first axis Y and the extension direction of the recesses 51. In this embodiment, the specific direction coincides with the direction along the second axis Z. The seven recesses 51 all have the same dimension H4 in the specific direction. Furthermore, the six protrusions 52 located between adjacent recesses 51 all have the same dimension H5 in the specific direction. The dimension H5 in the specific direction of the protrusions 52 located between adjacent recesses 51 is larger than the dimension H4 in the specific direction of the recesses 51. In other words, the ratio of the dimension H5 in the specific direction of the protrusions 52 to the sum of the dimension H4 in the specific direction of the recesses 51 and the dimension H5 in the specific direction of the protrusions 52 is 50% or more.
[0061] Furthermore, the maximum dimension T2 in the direction along the first axis Y from the tip of adjacent convex portions 52 to the bottom of the concave portion 51 is 10 μm or more. When the maximum dimension T2 can be measured at multiple locations as in the second embodiment, the maximum dimension T2 is measured at three or more locations, and if the average value of the maximum dimensions T2 is 10 μm or more, it is determined that "the maximum dimension T2 is 10 μm or more."
[0062] 4 , the portion of the wire 70 that is joined to the external electrode 40 is defined as a joint EP. That is, a portion of the wire 70 that includes the first end and a portion of the wire 70 that includes the second end are the joint EP.
[0063] The joint EP is compressed by thermocompression bonding, reducing its thickness in the direction along the first axis Y. The dimension of the joint EP in the direction along the first axis Y is approximately 10 μm. When viewed in the first negative direction Y2, the joint EP has a substantially elliptical shape.
[0064] The joint EP spans two recesses 51 and one protrusion 52. Both ends of the joint EP in the direction along the second axis Z are located on different protrusions 52. Note that the definition of "the joint EP spans the recesses 51" is the same as in the first embodiment. Furthermore, the portion of the joint EP facing the recesses 51 may not be in direct contact with the external electrode 40. Even in this case, the portion of the wire 70 facing the external electrode 40 in the direction along the first axis Y is considered to be the joint EP.
[0065] 4, the dimension H4 of the recess 51 in the specific direction is smaller than the dimension H6 of the joint EP in the specific direction. In this embodiment, the dimension H6 of the joint EP in the specific direction is the dimension along the second axis Z from the point of the joint EP closest to the second positive direction Z1 to the point of the joint EP closest to the second negative direction Z2.
[0066] Here, when viewed in the first negative direction Y2, an imaginary line V is drawn in the direction along the central axis X, passing through the point of the joint EP that is farthest from the winding core portion 11 and the point of the joint EP that is closest to the winding core portion 11. In this embodiment, the point of the joint EP that is closest to the winding core portion 11 is a linear point of the joint EP that overlaps with a portion of the external electrode 40 that extends parallel to the second axis Z on the winding core portion 11 side. In this case, the midpoint of this linear point is defined as the point of the joint EP that is closest to the winding core portion 11. The acute angle α formed by the imaginary line V and the central axis X is 45 degrees. In other words, the acute angle α formed by the imaginary line V and the extension direction of the recess 51 is greater than or equal to 40 degrees and less than 90 degrees.
[0067] <Effects of Second Embodiment> In the second embodiment, in addition to the effects (1-1), (1-2), and (1-4) to (1-7) of the first embodiment, the following effects can be further obtained.
[0068] (2-1) In the second embodiment, the recesses 51 extend in a direction along the central axis X. When the recesses 51 extend in a direction along the central axis X in this manner, the extension length of each recess 51 is shorter than when the recesses 51 extend in other directions. Therefore, steam is less likely to flow out of the recesses 51 while circulating inside the recesses 51. Therefore, with the above configuration, steam can be released in the intended direction.
[0069] (2-2) In the second embodiment, the base electrode layer 41 has an electrode recess 61 recessed in the first negative direction Y2. The recess 51 covers the electrode recess 61. In the above configuration, the recess 51 is formed to reflect the shape of the electrode recess 61. That is, with the above configuration, the recess 51 can be formed without forming irregularities on the flange portion 20. Because there is no need to form irregularities on the flange portion 20, the mold for manufacturing the drum-shaped core 10C is less likely to become complicated. Furthermore, if irregularities are to be formed on the outer surface of the flange portion 20 facing the first positive direction Y1, it is necessary to identify the surface with the irregularities and adjust the orientation of the flange portion 20 before forming the external electrode 40. With the above configuration, there is no need to identify such irregular surfaces and adjust the orientation, which prevents the coil component 10 from requiring additional manufacturing steps.
[0070] <Modifications> The above-described embodiment can be modified as follows: The above-described first embodiment, second embodiment, and the following modifications can be combined and implemented within a range that does not cause technical contradictions.
[0071] In the first and second embodiments, the configuration of the coil component 10 is not limited to the above configuration. For example, the coil component 10 may further include a plate-shaped core that spans between the first flange portion 21 and the second flange portion 22.
[0072] In the first and second embodiments, the shape of the winding core 11 is not limited to the examples of the above embodiments. For example, the shape of the winding core 11 may be an elliptical cylinder or a polygonal cylinder other than a quadrangular cylinder.
[0073] In the first and second embodiments, the coil component 10 may include two or more wires 70. When the coil component 10 includes two wires 70, the coil component 10 may further include an external electrode attached to the first flange 21 side and an external electrode attached to the second flange 22 side. The second wire may be connected to each of these external electrodes.
[0074] In the first and second embodiments, the shape of the wire 70 is not limited to the examples in the above embodiments. When viewed in a cross section perpendicular to the direction in which the wire 70 extends, the shape of the wire 70 may be an ellipse other than a circle, or a polygon.
[0075] In the first and second embodiments, the layer structure of each external electrode 40 is not limited to the examples in the above embodiments. For example, the external electrode 40 may have at least one conductive layer. Furthermore, the material of the external electrode 40 is not limited to silver, nickel, copper, or tin, which are exemplified in the above embodiments.
[0076] In the first and second embodiments, the materials of the drum-shaped core 10C and the winding core 11 are not limited to those of the above-described embodiments. For example, the materials of the drum-shaped core 10C and the winding core 11 are not limited to Ni-Zn ferrite, but may be Mn-Zn ferrite, etc. Furthermore, the materials of the drum-shaped core 10C and the winding core 11 may be ferrite, alumina, synthetic resin, a mixture thereof, etc.
[0077] In the first embodiment, the recesses 51 are not limited to depressions in the plating layer 42. In the example shown in Fig. 6, the surface of each flange 20 facing the first positive direction Y1 is flat. The base electrode layer 41 of each external electrode 40 is in contact with a flat portion of the outer surface of the flange 20. The plating layer 42 is laminated on the base electrode layer 41 on the first positive direction Y1 side.
[0078] 6 , each external electrode 40 has a plurality of recesses 51 and a plurality of protrusions 52. Specifically, each external electrode 40 has three recesses 51 and four protrusions 52. Each recess 51 and each protrusion 52 faces the first positive direction Y1 side of the external electrode 40.
[0079] Each recess 51 is a portion of the external electrode 40 that is recessed in the first negative direction Y2. In the example shown in Fig. 6, the recess 51 penetrates the external electrode 40 in the direction along the first axis Y. That is, the bottom surface of the recess 51 is the surface of the flange portion 20 that faces the first positive direction Y1. Note that even when the recess 51 penetrates the external electrode 40 in this way, the external electrode 40 can be said to have a recess 51 if it has a portion that is recessed in the first negative direction Y2 with respect to the tip surface of the external electrode 40 in the first positive direction Y1.
[0080] 6, when viewed in the first negative direction Y2, each recess 51 extends linearly in a direction along the second axis Z. The recesses 51 extend parallel to one another at equal intervals. Note that the term "extending linearly" has the same definition as in the first embodiment.
[0081] 6 , the protrusions 52 are portions of the external electrode 40 that protrude in the first positive direction Y1. Each protrusion 52 is located adjacent to a recess 51 in the direction along the central axis X. Therefore, two of the four protrusions 52 are located between the recesses 51 in the direction along the central axis X. The remaining two protrusions 52 are located at the end of the external electrode 40 on the positive direction X1 side and the end on the negative direction X2 side, respectively.
[0082] In the example shown in FIG. 6 , the boundary between the recess 51 and the protrusion 52 can be determined in the same manner as in the first embodiment. That is, as shown in FIG. 7 , assume an end view of a cross section perpendicular to the extension direction of the recess 51. Then, for adjacent protrusions 52 and recesses 51, the midpoints of lines parallel to the first axis Y passing through the tip of the protrusion 52 and the bottom of the recess 51 are identified. Then, a fourth approximate line AS4 is drawn to each of the identified midpoints. The portion of the external electrode 40 located on the first positive direction Y1 side of the fourth approximate line AS4 is the protrusion 52. The portion of the external electrode 40 located on the first negative direction Y2 side of the fourth approximate line AS4 is the recess 51. The boundary between the recess 51 and the protrusion 52 does not have to coincide with the boundary between the base electrode layer 41 and the plating layer 42. In the example shown in FIG. 6 , the surface of the flange 20 facing the first positive direction Y1 does not have to be flat. That is, in the example shown in FIG. 6 , the coil component 10 may have a core recess 31 and a core protrusion 32 .
[0083] In the example shown in FIG. 6 , the specific direction is defined as a direction perpendicular to the first axis Y and the extension direction of the recesses 51. In this embodiment, the specific direction coincides with the direction along the central axis X. As shown in FIG. 7 , the four recesses 51 each have the same dimension H7 in the specific direction. Furthermore, the two protrusions 52 located between adjacent recesses 51 each have the same dimension H8 in the specific direction. The dimension H8 in the specific direction of the protrusion 52 located between adjacent recesses 51 is larger than the dimension H7 in the specific direction of the recess 51. That is, the ratio of the dimension H8 in the specific direction of the protrusion 52 to the sum of the dimension H7 in the specific direction of the recess 51 and the dimension H8 in the specific direction of the protrusion 52 is 50% or more. Furthermore, the maximum dimension T3 in the direction along the first axis Y from the tip of the adjacent protrusion 52 to the bottom of the recess 51 is 10 μm or more.
[0084] This also applies to the second embodiment. In the example shown in FIG. 8 , the surface of each flange 20 facing the first positive direction Y1 is flat. Each external electrode 40 has multiple recesses 51 and multiple protrusions 52. Specifically, each external electrode 40 has seven recesses 51 and eight protrusions 52. Each recess 51 and each protrusion 52 faces the first positive direction Y1 side of the external electrode 40. Each recess 51 is a portion of the external electrode 40 recessed in the first negative direction Y2. In the example shown in FIG. 8 , the recess 51 penetrates the external electrode 40 in the direction along the first axis Y. That is, the bottom surface of the recess 51 is the surface of the flange 20 facing the first positive direction Y1. In the example shown in FIG. 8 , when viewed in the first negative direction Y2, each recess 51 extends linearly in the direction along the central axis X. The multiple recesses 51 extend parallel to one another at equal intervals.
[0085] 8 , the protrusions 52 are portions of the external electrode 40 that protrude in the first positive direction Y1. Each protrusion 52 is located adjacent to a recess 51 in the direction along the second axis Z. Therefore, six of the eight protrusions 52 are located between the recesses 51 in the direction along the second axis Z. The remaining two protrusions 52 are located at the end of the external electrode 40 on the second positive direction Z1 side and the end on the second negative direction Z2 side, respectively.
[0086] In the first and second embodiments, the recess 51 does not have to extend linearly when viewed in the first negative direction Y2. For example, the recess 51 may have a circular shape when viewed in the first negative direction Y2.
[0087] In the first and second embodiments, the number of recesses 51 and protrusions 52 is not limited to the examples in the above embodiments. The external electrode 40 only needs to have at least one recess 51. Furthermore, in the coil component 10, as long as at least one external electrode 40 has a recess 51, the other external electrode 40 does not need to have a recess 51.
[0088] In the first and second embodiments, the recess 51 may extend in a direction intersecting both the central axis X and the second axis Z. In the first and second embodiments, the acute angle α formed by the imaginary line V and the extension direction of the recess 51 may be less than 40 degrees. Furthermore, as long as the joint EP straddles the recess 51, the imaginary line V and the extension direction of the recess 51 may be parallel, or the angle formed by the imaginary line V and the extension direction of the recess 51 may be 90 degrees. Note that when the angle formed by the imaginary line V and the extension direction of the recess 51 is 90 degrees, sufficient bonding strength of the wire 70 to the external electrode 40 can be ensured.
[0089] In the first embodiment, the recess 51 does not have to be open in the direction along the second axis Z in the external electrode 40. That is, in the first embodiment, the recess 51 does not reach the end of the external electrode 40 on the second positive direction Z1 side and the end on the second negative direction Z2 side, and the protrusion 52 may be adjacent to the recess 51 in the direction along the second axis Z. This also applies to the second embodiment.
[0090] In the first embodiment, as long as the joint EP straddles the recess 51, the dimension H1 of the recess 51 in the specific direction may be smaller than the dimension H3 of the joint EP in the specific direction. This also applies to the second embodiment.
[0091] In the first embodiment, the ratio of the dimension H2 in the specific direction of the convex portion 52 to the sum of the dimension H1 in the specific direction of the concave portion 51 and the dimension H2 in the specific direction of the convex portion 52 may be less than 50%. This also applies to the second embodiment.
[0092] In the first embodiment, the maximum dimension T1 from the tip of the convex portion 52 to the bottom of the concave portion 51 along the first axis Y may be smaller than 10 μm. This also applies to the second embodiment.
[0093] <Supplementary Notes> The technical ideas that can be understood from the above-described embodiments and modified examples will be described below. [1] A coil component comprising: a drum-shaped core having a columnar winding core and a pair of flanges connected to the winding core in a direction along the central axis of the winding core, an external electrode covering an outer surface of the flange, and a wire wound around the winding core and joined to the external electrode, wherein 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 a direction opposite to the positive direction is defined as a negative direction, the external electrode covers a surface of the outer surface of the flange facing the positive direction, the external electrode has a recess that is recessed in the negative direction, and when a portion of the wire joined to the external electrode is defined as a joint portion, the joint portion straddles the recess.
[0094] [2] The coil component according to [1], wherein when viewed in the negative direction, the recess extends linearly. [3] The coil component according to [2], wherein when an axis perpendicular to both the central axis and the first axis is defined as a second axis, the recess extends in a direction along the second axis.
[0095] [4] The coil component according to [2], wherein the recess extends in a direction along the central axis. [5] The coil component according to any one of [2] to [4], wherein, when viewed in the negative direction, an acute angle formed by an imaginary line passing through a point of the joint portion farthest from the winding core portion and a point of the joint portion closest to the winding core portion in the direction along the central axis and the extending direction of the recess is 40 degrees or more and less than 90 degrees, or the angle formed by the imaginary line and the extending direction of the recess is 90 degrees.
[0096] [6] A coil component according to any one of [2] to [5], wherein when a direction perpendicular to the first axis and the extension direction of the recess is defined as a specific direction, the dimension of the recess in the specific direction is smaller than the dimension of the joint in the specific direction.
[0097] [7] The coil component described in any one of [2] to [6], wherein the external electrode comprises a plurality of recesses extending parallel to one another and protrusions located between the recesses and protruding in the positive direction, and when a direction perpendicular to the first axis and the direction in which the recesses extend is defined as a specific direction, the ratio of the dimension of the protrusions in the specific direction to the sum of the dimension of the recesses in the specific direction and the dimension of the protrusions in the specific direction is 50% or more.
[0098] [8] A coil component according to any one of [1] to [7], wherein the external electrode further comprises a protrusion adjacent to the recess and protruding in the positive direction, and the maximum dimension in the direction along the first axis from the tip of the protrusion to the bottom of the recess is 10 μm or more.
[0099] [9] A coil component according to any one of [1] to [8], wherein the flange portion has a core recess recessed in the negative direction, and the recess is a portion of the external electrode that covers the core recess.
[0100]
[10] A coil component according to any one of [1] to [8], wherein a portion of the outer surface of the flange is flat, and the external electrode comprises a base electrode layer in contact with the flat portion of the outer surface of the flange, and a plating layer laminated on the base electrode layer on the positive direction side, the base electrode layer having an electrode recess recessed in the negative direction, and the recess being a portion of the plating layer that covers the electrode recess.
[0101]
[11] A core component for a coil component, comprising: a drum-shaped core having a columnar winding core and a pair of flanges connected to the winding core in a direction along the central axis of the winding core; and an external electrode covering the 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 the direction opposite to the positive direction is defined as a negative direction, the external electrode covers the surface of the outer surface of the flange facing the positive direction, and the external electrode has a recess that is recessed in the negative direction, and when viewed facing the negative direction, the recess extends linearly.
[0102] α...acute angle EP...joint portion V...imaginary straight line X...central axis Y1...first positive direction Y2...first negative direction 10...coil component 10C...drum-shaped core 11...winding core portion 20...flange portion 31...core recess 32...core protrusion 40...external electrode 41...base electrode layer 42...plating layer 51...recess 52...protrusion 61...electrode recess 70...wire
Claims
1. A coil component comprising: a drum-shaped core having a columnar winding core and a pair of flanges connected to the winding core in a direction along the central axis of the winding core; an external electrode covering the outer surface of the flange; and a wire wound around the winding core and joined to the external electrode, wherein 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 external electrode covers the surface of the outer surface of the flange facing the positive direction, the external electrode has a recess that is recessed in the negative direction, and when the portion of the wire joined to the external electrode is defined as a joint, the joint straddles the recess.
2. The coil component according to claim 1, wherein the recess extends linearly when viewed in the negative direction.
3. The coil component according to claim 2, wherein, when an axis perpendicular to both the central axis and the first axis is defined as a second axis, the recess extends in a direction along the second axis.
4. The coil component according to claim 2, wherein the recess extends in a direction along the central axis.
5. A coil component according to any one of claims 2 to 4, wherein, when viewed in the negative direction, in a direction along the central axis, an acute angle formed by an imaginary line passing through a point of each of the joints farthest from the winding core and a point of each of the joints closest to the winding core and a direction in which each of the recesses extends is equal to or greater than 40 degrees and less than 90 degrees, or the angle formed by the imaginary line and the direction in which each of the recesses extends is 90 degrees.
6. A coil component according to any one of claims 2 to 5, wherein, when a direction perpendicular to the first axis and the extending direction of the recess is defined as a specific direction, the dimension of the recess in the specific direction is smaller than the dimension of the joint in the specific direction.
7. A coil component according to any one of claims 2 to 6, wherein the external electrode comprises a plurality of recesses extending parallel to one another and protrusions located between the recesses and protruding in the positive direction, and when a direction perpendicular to the first axis and the direction in which the recesses extend is defined as a specific direction, the ratio of the dimension of the protrusions in the specific direction to the sum of the dimension of the recesses in the specific direction and the dimension of the protrusions in the specific direction is 50% or more.
8. A coil component according to any one of claims 1 to 7, wherein the external electrode further comprises a protrusion adjacent to the recess and protruding in the positive direction, and the maximum dimension along the first axis from the tip of the protrusion to the bottom of the recess is 10 μm or more.
9. A coil component according to any one of claims 1 to 8, wherein the flange portion has a core recess recessed in the negative direction, and the recess is a portion of the external electrode that covers the core recess.
10. A coil component according to any one of claims 1 to 8, wherein a portion of the outer surface of the flange is flat, the external electrode comprises a base electrode layer in contact with the flat portion of the outer surface of the flange, and a plating layer laminated on the base electrode layer on the positive side, the base electrode layer having an electrode recess recessed in the negative direction, and the recess being a portion of the plating layer that covers the electrode recess.
11. A core component for a coil component, comprising: a drum-shaped core having a columnar winding core and a pair of flanges connected to the winding core in a direction along the central axis of the winding core; and an external electrode covering the 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 the direction opposite to the positive direction is defined as a negative direction, the external electrode covers the surface of the outer surface of the flange facing the positive direction, and the external electrode has a recess that is recessed in the negative direction, and when viewed facing the negative direction, the recess extends linearly.