Coil component

Abstract

This invention relates to coil components that improve the bonding strength between the core and the top plate. The surface roughness of the top surface (9, 10) of the flange portion of the core is different from the surface roughness of the lower main surface (15) of the top plate (14). For example, the surface roughness of the lower main surface (15) of the top plate (14) is less than the surface roughness of the top surface (9, 10) of the flange portion of the core. A protrusion (21) protruding from the lower main surface of the top plate with the smaller surface roughness and contacting the top surface of the flange portion of the core is provided in the area where the lower main surface of the top plate and the top surface of the flange portion of the core face each other, separated by an adhesive. The protrusion increases the surface area of ​​the bonding surface of the top plate with the smaller surface roughness and provides an anchoring effect of the adhesive relative to the top plate. Furthermore, since the protrusion itself is held in place, the shear strength in the extending direction of the opposing surfaces of the top plate and the core is improved.

Description

[0001] This application is a divisional application of application number 2022 1 0814 366.7, filed on July 12, 2022, entitled "Coil Component". Technical Field

[0002] The present invention relates to a coil component comprising: a core having a core portion on which wire is wound and a first flange portion and a second flange portion disposed at each end of the core portion; and a top plate being bonded and fixed to the core in a manner spanning between the first flange portion and the second flange portion, particularly relating to the structure of the bonding portion between the core and the top plate. Background Technology

[0003] For example, Japanese Patent Application Publication No. 2020-57656 (Patent Document 1) describes a coil component comprising: a core having a wound core portion on which wire is wound and a first flange portion and a second flange portion disposed at each end of the wound core portion; and a top plate bonded to the core body in a manner spanning between the first flange portion and the second flange portion. The bonding between the core body and the top plate uses an adhesive containing organic materials and fillers.

[0004] Patent Document 1 describes a technique that addresses the issue of improving the bonding strength between the core and the top plate. To solve this problem, the surface roughness of the surface of the core bonded to the top plate via an adhesive is larger than the average particle size of the filler. Furthermore, Patent Document 1 also describes a technique where the surface roughness of the surface of the top plate bonded to the core via an adhesive is smaller than the surface roughness of the surface of the core bonded to the top plate via an adhesive.

[0005] The technology described in Patent Document 1 aims to improve the bonding strength between the core and the top plate by allowing the filler to enter the recess on the top surface of the flange of the core, so that the flange of the core can be in direct contact with the top plate or closer to it through the adhesive.

[0006] Furthermore, in paragraph 0054 of Patent Document 1 and Figure 7, examples are described of two locations where the protrusion is provided on the side with greater surface roughness, i.e., the flange of the core, and is bonded to the surface of the top plate by an adhesive at two positions away from the center in the width direction. This is to avoid poor bonding between the core and the top plate due to undulations in the width direction of the top surface of the flange bending in the concave direction during the manufacturing process of the core. That is, by providing the approach portion at a position away from the center in the width direction of the flange by the protrusion, the stability during bonding can be improved, and as a result, the bonding strength can be improved.

[0007] Patent Document 1: Japanese Patent Application Publication No. 2020-57656

[0008] As described in Patent Document 1, when the surface roughness of the surface of the top plate bonded to the core via adhesive is less than the surface roughness of the surface of the core bonded to the top plate via adhesive, the anchoring effect of the adhesive relative to the top plate with a smaller surface roughness cannot be expected. Therefore, for example, the strength in the shear direction on the top plate side becomes relatively low, and the adhesive may easily peel off.

[0009] Furthermore, as described above, Patent Document 1 describes a case where a protrusion is provided on the flange portion of the core. However, since the protrusion is provided on the side with greater surface roughness, namely the flange portion of the core, the adhesive will not exhibit an anchoring effect relative to the top plate with less surface roughness. Summary of the Invention

[0010] Therefore, the object of the present invention is to provide a structure in a coil component that can improve the bonding strength between the core and the top plate.

[0011] The present invention relates to a coil component comprising: a core having a first flange portion, a second flange portion, and a winding core portion extending along an axial direction, wherein the first flange portion and the second flange portion are respectively disposed at a first end and a second end of the winding core portion opposite to each other in the axial direction; a top plate having a lower main surface and an upper main surface facing opposite directions; and at least one wire wound around the winding core portion.

[0012] The first flange portion and the second flange portion have: a first bottom surface and a second bottom surface facing the mounting substrate side during installation; and a first top surface and a second top surface opposite to the first bottom surface and the second bottom surface, respectively. The top plate is fixed to the core with the aforementioned lower main surface facing the aforementioned first top surface and second top surface in a state separated by adhesive.

[0013] In such a coil component, the characteristic is that, in order to solve the above-mentioned technical problem, the surface roughness of at least one of the first top surface and the second top surface of the core is different from the surface roughness of the lower main surface of the top plate. When the surface roughness of at least one of the first top surface and the second top surface and the lower main surface is taken as the first surface and the surface roughness of the second surface is taken as the second surface, at least one protrusion protruding from the first surface and contacting the second surface is provided in the area where the first surface and the second surface are opposite each other through an adhesive.

[0014] Furthermore, surface roughness can be measured, for example, using a laser microscope "VK-X1000" within any 1 / 3 of the field of view of the objective lens ×20, and analyzed using analysis software, and determined based on the unfolded area ratio of the Sdr interface.

[0015] According to the present invention, since at least one protrusion is provided that protrudes from a first surface with a smaller surface roughness and contacts a second surface with a larger surface roughness, the surface area of ​​the bonding surface of the first surface with a smaller surface roughness can be increased, and an anchoring effect of the adhesive relative to the first surface can be obtained. Furthermore, since the protrusion itself is held in place, the shear strength in the extending direction of the opposing first and second surfaces can be improved. Therefore, in the coil component, the bonding strength between the core and the top plate can be improved, and a coil component with excellent impact resistance and vibration resistance can be obtained. Attached Figure Description

[0016] Figure 1 This is a front view showing the appearance of the coil component 1 according to the first embodiment of the present invention.

[0017] Figure 2 It means Figure 1 The diagram shows the top plate 14 of the coil component 1 shown. (A) is the front view and (B) is the bottom view.

[0018] Figure 3 It is an enlarged cross-sectional view schematically showing the protrusion 21 located in the area opposite to the core 2 and the top plate 14.

[0019] Figure 4 This is a top view showing the core 2a of the coil component according to the second embodiment of the present invention.

[0020] Explanation of reference numerals in the attached figures

[0021] 1…coil component; 2, 2a…core; 3…winding core; 5, 6…flange; 7, 8…bottom surface; 9, 10…top surface; 11, 12…terminal electrode; 13…wire; 14…top plate; 15…lower main surface; 16…upper main surface; 17…adhesive; 21, 22…protrusion. Detailed Implementation

[0022] Reference Figure 1 The coil component 1 of the first embodiment of the present invention will be described.

[0023] like Figure 1 As shown, the coil component 1 includes a core 2 made of ferrite such as Ni-Zn ferrite, alumina, or resin containing metallic magnetic powder. The core 2 has a winding core portion 3 extending along the axial direction AX, and a first flange portion 5 and a second flange portion 6 respectively disposed at opposite ends on the axial direction AX of the winding core portion 3. The cross-sectional shape of the winding core portion 3 is, for example, a quadrilateral shape, but it can also be a polygonal shape such as a hexagon, a circular shape, an elliptical shape, or a combination thereof.

[0024] The first flange portion 5 and the second flange portion 6 each have a first bottom surface 7 and a second bottom surface 8 facing the mounting substrate (not shown) during installation, and a first top surface 9 and a second top surface 10 on the opposite side of the first bottom surface 7 and the second bottom surface 8, respectively.

[0025] A first terminal electrode 11 is provided on the bottom surface 7 of the first flange portion, and a second terminal electrode 12 is provided on the bottom surface 8 of the second flange portion 6. The terminal electrodes 11 and 12 are formed, for example, by impregnating or printing a conductive paste containing conductive metal powder such as Ag powder, then sintering them, and subsequently performing Cu, Ni, and Sn plating in sequence. Alternatively, the terminal electrodes 11 and 12 can also be provided by mounting terminal components made of conductive metal plates onto the flange portions 5 and 6.

[0026] At least one wire 13 is wound in the core portion 3. The wire 13 may have a center wire made of a highly conductive metal such as copper, silver, or gold, and an insulating film covering the center wire made of an electrically insulating resin such as polyamide-imide, polyurethane, or polyesterimide. The center wire has a diameter of, for example, 60 μm or more and 160 μm or less. One end of the wire 13 is connected to the first terminal electrode 11, and the other end is similarly connected to the second terminal electrode 12. The connection between the terminal electrodes 11 and 12 and the wire 13 is achieved, for example, by thermoforming, ultrasonic welding, or laser welding. The number of turns of the wire 13 in the core portion 3 can be arbitrarily selected according to the desired characteristics. The wire 13 may also be wound in multiple layers as needed.

[0027] The coil component 1 includes a top plate 14 spanning between the first flange portion 5 and the second flange portion 6. The top plate 14 has a lower main surface 15 and an upper main surface 16 facing opposite directions. The top plate 14 is made of, for example, ferrite, alumina, or resin containing metallic magnetic powder. Furthermore, when both the core 2 and the top plate 14 are made of magnetic materials, the top plate 14 and the core 2 cooperate to form a closed magnetic circuit.

[0028] The top plate 14 is fixed to the core 2 with its lower main surface 15 facing the top surface 9 of the first flange portion 5 and the top surface 10 of the second flange portion 6 through the adhesive 17. The adhesive 17 includes, for example, a thermosetting resin such as an epoxy resin. To improve thermal shock resistance, inorganic fillers such as silica fillers may be added to the adhesive 17.

[0029] Taking coil component 1 as an example, its length (axial direction AX) dimension is 2.0 mm, and its width ( Figure 2 (B) The vertical dimension is 1.2mm, and the height dimension is ( Figure 1 The dimension (vertical direction) is 1.6mm.

[0030] The coil component 1 is preferably manufactured as follows, for example.

[0031] First, core 2 and top plate 14 are prepared separately. To manufacture these core 2 and top plate 14 separately, ferrite powder is stamped using a mold, and the resulting molded body is fired to obtain a sintered body that should become core 2 and top plate 14. Then, burrs are removed by tumbling the sintered body that corresponds to core 2 and top plate 14, respectively, to obtain core 2 and top plate 14. Although in Figure 1 and Figure 2 The diagram is omitted, but the edges of the core 2 and the top plate 14 are chamfered and have small rounded corners.

[0032] Next, in order to provide terminal electrodes 11 and 12 on the core 2, conductive paste containing Ag is applied to the bottom surfaces 7 and 8 of the first flange portion 5 and the second flange portion 6, and sintered. Then, Cu, Ni and Sn are plated sequentially by electrolytic barrel plating.

[0033] Next, for example, the wire 13 is wound onto the core portion 3 of the core 2 through a nozzle, and one end of the wire 13 is connected to the first terminal electrode 11 and the second terminal electrode 12, respectively. Here, the connection between the wire 13 and the terminal electrodes 11 and 12 is achieved, for example, by thermocompression bonding based on a heating element. The excess portion of the wire 13 connected to the terminal electrodes 11 and 12 is cut off and removed by a cutter.

[0034] As described above, complete coil component 1.

[0035] The coil component 1 has the following characteristics.

[0036] First, it is characterized in that the surface roughness of at least one of the first top surface 9 and the second top surface 10 of the core 2 is different from the surface roughness of the lower main surface 15 of the top plate 14. Second, it is characterized in that when the surface roughness of at least one of the first top surface 9 and the second top surface 10 and the lower main surface 15 is used as the first surface and the surface roughness of the second surface is used as the second surface, at least one protrusion 21 protruding from the first surface and in contact with the second surface is disposed in the area where the first surface and the second surface are opposite each other separated by the adhesive 17.

[0037] In this embodiment, such as Figure 3 As schematically shown, the first surface with a smaller surface roughness is the lower main surface 15 of the top plate 14, and the second surface with a larger surface roughness is the first top surface 9 and the second top surface 10 of the core 2. Therefore, as Figure 2As shown, protrusion 21 is disposed on the lower main surface 15 of the top plate 14. More specifically, protrusion 21 is disposed in the area where the top plate 14 and the core 2 are separated by adhesive 17, that is, two parts of the lower main surface 15 of the top plate 14 that are opposite each other to the first top surface 9 and the second top surface 10. In order to understand the positional relationship between the lower main surface 15 of the top plate 14 and the first top surface 9 and the second top surface 10, Figure 2 In the bottom view of the top plate 14 of (B), the outlines of the first top surface 9 and the second top surface 10 are shown with dashed lines.

[0038] Furthermore, in the area where the lower main surface 15 of the top plate 14 faces the first top surface 9, a plurality of protrusions 21, such as two protrusions, are provided. Similarly, in the area where the lower main surface 15 of the top plate 14 faces the second top surface 10, a plurality of protrusions 21, such as two protrusions, are provided. These protrusions 21 are arranged symmetrically with respect to the surface containing the central axis of the core portion 3 and orthogonal to the lower main surface 15, and are also arranged symmetrically with respect to the surface orthogonal to the central axis of the core portion 3 and passing through the midpoint of the axial direction AX of the core portion 3.

[0039] If the multiple protrusions 21 are arranged in symmetrical positions as described above, it is possible to prevent the top plate 14 from tilting relative to the core 2 and to stabilize the posture of the top plate 14 relative to the core 2. This makes it easier to keep the distance between the core 2 and the top plate 14 constant.

[0040] The protrusion 21 is, for example, truncated cone-shaped. Therefore, its apex is not a point, but a plane. By forming the protrusion 21 as a truncated cone, compared to forming it as a cylinder, defects in the protrusion 21 are less likely to occur during manufacturing. Furthermore, compared to a point apex, it is less prone to wobbling when assembling the core 2 and the top plate 14, allowing for stable assembly. (Refer to...) Figure 3 For example, the diameter D1 of the bottom surface is 150 μm or more and 250 μm or less, the diameter D2 of the top surface is 100 μm or more and 200 μm or less, and the height H is 20 μm or more and 60 μm or less.

[0041] According to the first embodiment described above, since multiple protrusions 21 are provided that protrude from the lower main surface 15 of the top plate 14, which has a smaller surface roughness, and contact the top surfaces 9 and 10 of the core 2, which has a larger surface roughness, the surface area of ​​the bonding surface of the lower main surface 15 of the top plate 14, which has a smaller surface roughness, can be increased, and the anchoring effect of the adhesive 17 relative to the lower main surface 15 of the top plate 14 can be obtained. In addition, since the protrusions 21 themselves are held in place, the shear strength in the extending direction of the opposing surfaces of the top plate 14 and the core 2 can be improved. Therefore, in the coil component 1, the bonding strength between the core 2 and the top plate 14 can be improved, and the coil component 1 can have excellent impact resistance and vibration resistance.

[0042] In addition, the protrusion 21 creates a certain gap between the core 2 and the top plate 14. This gap helps to improve the DC superposition characteristics of the inductor when the coil component 1 functions as an inductor.

[0043] As described in the first embodiment above, if the protrusion 21 is provided on the top plate 14, the complexity of the mold and manufacturing can be avoided compared to the case where it is provided on the core 2. However, if such advantages are not particularly desired, the protrusion can also be provided on the core 2 as described in the second embodiment below. Furthermore, in the second embodiment, no protrusion is provided on the top plate.

[0044] Figure 4 This is a top view showing the core 2a of the coil component according to the second embodiment of the present invention. Figure 4 In the middle, to and Figure 1 or Figure 2 Elements that are equivalent to those shown are labeled with the same reference numerals as those in the attached drawings, and repeated descriptions are omitted.

[0045] In the second embodiment, the surface roughness relationship is reversed compared to the first embodiment, such that the first surface with smaller surface roughness is at least one of the first top surface 9 and the second top surface 10 of the core 2a, and the second surface with larger surface roughness is the lower main surface of the top plate. Therefore, as Figure 4 As shown, the protrusion 22 is disposed on at least one of the first top surface 9 and the second top surface 10 of the core 2a. In this embodiment, it is disposed on both the first top surface 9 and the second top surface 10 of the core 2a. The protrusion 22 is the same as the protrusion 21 described above, for example, it is truncated cone-shaped.

[0046] In addition, a plurality of protrusions 22, for example two, are provided on the first top surface 9 and the second top surface 10 respectively. These protrusions 22 are arranged symmetrically with respect to the surface containing the central axis of the core portion 3 and orthogonal to the lower main surface of the top plate, and are also arranged symmetrically with respect to the surface orthogonal to the central axis of the core portion 3 and passing through the midpoint of the axial direction AX of the core portion 3.

[0047] In the second embodiment, as in the first embodiment, if the plurality of protrusions 22 are arranged in symmetrical positions as described above, it is possible to prevent the top plate from tilting relative to the core 2a and to stabilize the posture of the top plate relative to the core 2a.

[0048] According to the second embodiment described above, since multiple protrusions 22 are provided that protrude from the first top surface 9 and the second top surface 10 of the core 2a, which have lower surface roughness, and contact the lower main surface of the top plate, which has higher surface roughness, the surface area of ​​the bonding surfaces of the first top surface 9 and the second top surface 10 of the core 2a, which have lower surface roughness, can be increased, and an anchoring effect of the adhesive relative to the first top surface 9 and the second top surface 10 of the core 2a can be obtained. Furthermore, since the protrusions 22 themselves are held in place, the shear strength in the extending direction of the opposing surfaces of the core 2a and the top plate can be improved. Therefore, in the coil component, the bonding strength between the core 2a and the top plate can be improved, resulting in excellent impact resistance and vibration resistance of the coil component.

[0049] Furthermore, in the first and second embodiments, the plurality of protrusions 21 or 22 may not necessarily be arranged in symmetrical positions. For example, associated with the first embodiment, the protrusion 21 may only be provided on the portion of the lower main surface 15 of the top plate 14 opposite to one of the first top surface 9 and the second top surface 10. Associated with the second embodiment, the protrusion 22 may only be provided on one of the first top surface 9 and the second top surface 10.

[0050] As described above, the coil component 1 according to the first and second embodiments has the following feature: the surface roughness of at least one of the first top surface 9 and the second top surface 10 of the core 2 or 2a is different from the surface roughness of the lower main surface 15 of the top plate 14. Various methods are used to control the surface roughness in this way, such as methods that make the materials of the core and the top plate different, methods that make the smoothness of the mold used to form the core and the mold used to form the top plate different, methods that make the firing temperature and firing time different during the firing of the core and the firing of the top plate, and methods that make the time for tumbling after firing different in the core and the top plate, etc.

[0051] For example, when using a method that involves different grinding times in the core and top plate, if the surface roughness is expressed as the ratio of the unfolded area of ​​the Sdr interface (the increase in surface area compared to a flat surface), it can be 0.04~0.12 within 50 minutes of grinding and 0.15~0.22 within 60 minutes of grinding. That is, the longer the grinding time, the more collisions of the grinding media, and therefore the greater the surface roughness.

[0052] Furthermore, the aforementioned surface roughness was determined, for example, by measuring the height of the sample surface using a laser microscope “VK-X1000” and analyzing it using analytical software.

[0053] Specifically, in flanges 5 and 6, the flat portions of the first top surface 9 and the second top surface 10, excluding the protrusions and surrounding edges, are calculated based on the unfolded area ratio of the Sdr interface within any 1 / 3 range of the field of view of objective lens × 20. On the other hand, in top plate 14, the flat portions of the lower main surface 15, excluding the protrusions and surrounding edges, are calculated by averaging the unfolded area ratio of the Sdr interface within any 1 / 3 range of the field of view of objective lens × 20.

[0054] In addition, to control the surface roughness of the core and top plate, a method can be adopted where the materials of the core and top plate are different from each other. For example, the top plate can be made of ferrite with a permeability of about 22, and the core can be made of ferrite with a permeability of about 1000. This combination can help improve the DC superposition characteristics within a range where the protrusion is not too high.

[0055] The present invention has been described above in connection with the illustrated embodiments, but various other modifications are possible within the scope of the present invention.

[0056] For example, in addition to being a single coil as shown in the illustrated embodiment, or a common-mode choke coil, the coil component involved in this invention can also be a transformer, a balun, or the like. Therefore, the number of wires can be changed according to the function of the coil component, and correspondingly, the number of terminal electrodes provided on each flange can also be changed.

[0057] Furthermore, when constructing the coil component involved in this invention, partial substitutions or combinations of structures can be made between the different embodiments described in this specification.

Claims

1. A coil component, wherein, have: The core has a first flange portion, a second flange portion, and a winding core portion extending along the axial direction, wherein the first flange portion and the second flange portion are respectively disposed at a first end and a second end opposite to each other in the axial direction of the winding core portion; The top panel has a lower main surface and an upper main surface facing opposite directions to each other; as well as At least one wire is wound around the core portion. The first flange portion and the second flange portion have: a first bottom surface and a second bottom surface facing the mounting substrate side during installation; and a first top surface and a second top surface on the opposite side of the first bottom surface and the second bottom surface, respectively. The top plate is fixed to the core with its lower main surface facing the first and second top surfaces through an adhesive. At least one protrusion, which protrudes from at least one of the first top surface and the second top surface and contacts the lower main surface, is disposed in the area where at least one of the first top surface and the second top surface is opposed to the lower main surface through the adhesive. The height of the protrusion is above 20 μm and below 60 μm.

2. The coil component according to claim 1, wherein, The first surface is the lower main surface of the top plate, and the second surface is at least one of the first top surface and the second top surface of the core.

3. The coil component according to claim 2, wherein, The protrusion is located on the portion of the lower main surface opposite to one of the first top surface and the second top surface.

4. The coil component according to claim 2, wherein, The protrusion is provided in two portions of the lower main surface opposite each of the first top surface and the second top surface.

5. The coil component according to claim 1, wherein, The first surface is at least one of the first top surface and the second top surface of the core, and the second surface is the lower main surface of the top plate.

6. The coil component according to claim 5, wherein, The protrusion is disposed on one of the first top surface and the second top surface.

7. The coil component according to claim 5, wherein, The protrusion is provided on both the first top surface and the second top surface.

8. The coil component according to any one of claims 1 to 7, wherein, The plurality of protrusions are disposed in an area where the first surface and the second surface are opposite each other, separated by the adhesive.

9. The coil component according to claim 8, wherein, The plurality of protrusions are arranged symmetrically relative to the surface containing the central axis of the core portion and orthogonal to the lower main surface.

10. The coil component according to claim 8 or 9, wherein, The plurality of protrusions are arranged symmetrically with respect to a surface that is orthogonal to the central axis of the core portion and passes through the midpoint of the core portion in the axial direction.

11. The coil component according to any one of claims 1 to 10, wherein, The core and the top plate are made of different materials.

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