Coil component

Abstract

The present invention provides a coil component in which a chamfered part is formed on a ceramic-containing top plate spanning between a first flange part and a second flange part provided to a core, thereby making cracking or chipping less likely to occur, and without incurring a substantial drop in inductance.　Each of the first flange part and the second flange part has a thickness between 0.4 mm and 0.7 mm, inclusive. In a ridge line portion (R) of a top plate (31) where a first main surface (33) and a lateral surface (35) intersect, a chamfered part (36) is provided in a range (S1) between 0.06 mm and 0.20 mm, inclusive, as measured in the direction orthogonal to the side surface (35), from the lateral surface (35) over the entire perimeter of the first main surface (33). A first convex roundness (37) is imparted to a region (S3) having a width between 0.01 mm and 0.05 mm, inclusive, along the inner peripheral edge of the chamfered part (36).

Description

Coil component

[0001] The present disclosure relates to a coil component including: a core having a winding core portion around which a wire is wound, and a first flange portion and a second flange portion respectively provided at a first end and a second end of the winding core portion in the axial direction; and a top plate bridged between the first flange portion and the second flange portion. In particular, the present disclosure relates to a coil component including a top plate provided with a chamfered portion to make the top plate less prone to cracking and chipping.

[0002] For example, Japanese Patent Application Laid-Open No. 2023-164653 (Patent Document 1) describes a coil component including a core having a winding core portion around which a wire is wound, and a first flange portion and a second flange portion respectively provided at each end of the winding core portion, and further including a top plate (magnetic plate) bridged between the first flange portion and the second flange portion of the core. The top plate cooperates with the core to form a closed magnetic circuit, and is mainly provided to increase the inductance value of the coil component.

[0003] Patent Document 1 describes that the material of the above-mentioned top plate is the same as the material of the core (paragraph 0056), and exemplifies sintered bodies such as ferrite and ceramics such as alumina as the material of the core (paragraph 0053). Therefore, it is understood that in one embodiment, the top plate contains ceramic.

[0004] In the coil component described in Patent Document 1, a chamfered portion (inclined surface) is provided at the peripheral edge of the main surface of the top plate. It is presumed that the chamfered portion is effective in making a ceramic-containing top plate less prone to cracking and chipping. Note that Patent Document 1 mentions a "chamfered portion" for reducing cracking and chipping of the top plate (paragraphs 0065 to 0068). However, the "chamfered portion" mentioned herein does not refer to the chamfered portion at the peripheral edge of the main surface of the top plate, but refers to a "chamfered portion" located at a ridge portion between adjacent ones of a plurality of "inclined surfaces" formed along the peripheral edge of the main surface of the top plate.

[0005] Japanese Patent Application Laid-Open No. 2023-164653

[0006] Patent Document 1 describes providing a chamfered portion (inclined surface) on the peripheral edge of the main surface of the top plate, as described above. The chamfered portion also acts to suppress magnetic saturation that may occur in the closed magnetic circuit structure formed by the core and the top plate, and is expected to improve the DC superposition characteristics of the coil components. Here, the larger the area occupied by the chamfered portion on the main surface of the top plate, the less cracking and chipping of the top plate can be reduced.

[0007] On the other hand, if the area occupied by the chamfered portion becomes too large, the magnetic efficiency between the core and the top plate decreases, and the inductance value decreases, so the effect of improving the inductance value by providing the top plate cannot be expected.

[0008] Patent Document 1 does not describe the area occupied by the chamfered portion. Therefore, it is desirable to provide conditions that suppress cracking and chipping of the top plate due to the chamfered portion, while not causing a substantial decrease in the inductance value.

[0009] Therefore, the purpose of this disclosure is to provide a coil component that satisfies the condition that the chamfered portion makes it less likely for cracks or chips to occur in the top plate containing ceramic, while not causing a substantial decrease in inductance value.

[0010] The coil component according to this disclosure comprises a core having a winding core portion extending in the axial direction and a first flange portion and a second flange portion provided at a first end portion and a second end portion opposite to each other in the axial direction of the winding core portion, respectively; a top plate containing ceramic, stretched between the first flange portion and the second flange portion; and at least one wire wound around the winding core portion.

[0011] Each of the first and second flanges has a bottom surface that faces the mounting substrate side during mounting, a top surface opposite the bottom surface, an inner end surface that connects the bottom surface and the top surface and faces the winding core side, where the axial end of the winding core is located, and an outer end surface that faces the opposite side of the inner end surface. Here, the thickness of each of the first and second flanges, which is the distance between the opposing inner and outer end surfaces, is always 0.4 mm or more and 0.7 mm or less.

[0012] The top plate has a first main surface facing the core, a second main surface facing the opposite side of the first main surface, and a side surface connecting the first and second main surfaces, and is fixed to the core with the first main surface facing the top surfaces of the first and second flanges, respectively.

[0013] On the top plate, a chamfer is provided along the ridge where the first main surface and the side surface intersect, in a range of 0.06 mm or more and 0.20 mm or less measured from the side surface in a direction perpendicular to the side surface, around the entire circumference of the first main surface. Furthermore, a first convex curve is provided in the area along the inner edge of the chamfer with a width of 0.01 mm or more and 0.05 mm or less.

[0014] According to the coil component described herein, the thickness of the flange and the area occupied by the chamfered portion on the ceramic-containing top plate are set to the conditions described above, making it possible to prevent cracking or chipping of the top plate while avoiding a substantial decrease in the inductance value.

[0015] Furthermore, this disclosure specifies preferred conditions regarding the thickness of the flange and the area occupied by the chamfered portion on the ceramic-containing top plate, thereby facilitating the design of coil components.

[0016] Figure 1 shows a perspective view of the coil component 1 according to the first embodiment of this disclosure, with the bottom surfaces 15 of the first flange portion 5 and the second flange portion 6 facing upward. Figure 1 shows an enlarged cross-sectional view of a part of the first flange portion 5 and a part of the top plate 31 of the core 2 provided in the coil component 1 shown in Figure 1. Figure 2 shows a cross-sectional view of a part of the top plate 31 shown in Figure 2, with the state before and after barrel polishing treatment being enlarged compared to Figure 2. Figure 2 shows an enlarged cross-sectional view of a part of the top plate 31a provided in the coil component according to the second embodiment of this disclosure, with the state before and after barrel polishing treatment being enlarged.

[0017] First, with reference to Figure 1, the overall configuration of the coil component 1 according to the first embodiment of this disclosure will be described. The illustrated coil component 1 constitutes, for example, a common mode choke coil.

[0018] The coil component 1 comprises a drum-shaped core 2. The core 2 has a winding core portion 3 extending in the axial direction AX, and a first flange portion 5 and a second flange portion 6 provided at the first and second ends of the winding core portion 3, opposite to each other in the axial direction AX. The core 2 is made of a magnetic material such as ferrite, alumina, or a resin containing metal magnetic powder. In the illustration, the cross-sectional shape of the winding core portion 3 is approximately square, but it may also be a polygon such as a hexagon, a circle, an ellipse, or a combination thereof.

[0019] Two wires 7 and 8 are wound around the core 3. In a common mode choke coil, as is well known, the two wires 7 and 8 are wound in the same direction around the core 3. The wires 7 and 8 comprise a core wire made of a highly conductive metal such as copper, silver, or gold, and an insulating coating made of an electrically insulating resin such as polyamide-imide, polyurethane, or polyester-imide covering the core wire. The diameters of the wires 7 and 8 are not particularly limited, but for example, those with a diameter of 20 μm or more and 60 μm or less can be used.

[0020] Each end of the first wire 7 is connected to the first metal terminal 9 and the second metal terminal 10, respectively. Each end of the second wire 8 is connected to the third metal terminal 11 and the fourth metal terminal 12, respectively. For connecting wires 7 and 8 to metal terminals 9 to 12, for example, thermocompression bonding is applied. In addition to thermocompression bonding, other connection methods such as laser welding, soldering, or connection with conductive adhesive may be used.

[0021] The metal terminals 9 to 12 are made of metal plates made of a copper-based alloy such as phosphor bronze or tough pitch copper. Preferably, the metal plates are tin-plated. The metal plates also have a thickness of, for example, 0.10 mm or more and 0.15 mm or less.

[0022] The first metal terminal 9 and the fourth metal terminal 12 have the same shape, and the second metal terminal 10 and the third metal terminal 11 have the same shape. Furthermore, the first metal terminal 9 and the second metal terminal 10 have symmetrical shapes, and the third metal terminal 11 and the fourth metal terminal 12, as shown in the figure, have symmetrical shapes.

[0023] The first metal terminal 9 and the third metal terminal 11 are arranged side by side in the width direction WD at the first flange portion 5. The second metal terminal 10 and the fourth metal terminal 12 are arranged side by side in the width direction WD at the second flange portion 6.

[0024] The first flange portion 5 and the second flange portion 6 have symmetrical shapes. Therefore, in describing the details of the first flange portion 5 and the second flange portion 6, the same reference numerals are used for corresponding parts.

[0025] Each of the first flange portion 5 and the second flange portion 6 has a bottom surface 15 that faces the mounting substrate side during mounting, a top surface 16 that faces the opposite side of the bottom surface 15, an inner end surface 17 that connects the bottom surface 15 and the top surface 16 and faces the winding core portion 3 side, where the end of the winding core portion 3 in the axial direction AX is located, and an outer end surface 18 that faces the opposite side of the inner end surface 17. The inner end surface 17 and the outer end surface 18 face each other in the axial direction AX.

[0026] A raised ridge 19 is provided at the center of the width direction WD of each outer end face 18 of the flange portions 5 and 6. The raised ridge 19 extends linearly in the height direction HD, which is perpendicular to the axial direction AX and is the direction in which the bottom surface 15 and the top surface 16 face each other.

[0027] Each of the bottom surfaces 15 of the flange portions 5 and 6 is provided with a raised shape in the center of the width direction WD, thereby creating a high surface 20 in the center, and on both sides of the high surface 20 in the width direction WD, there are low surfaces 22 that are located lower to the high surface 20 via stepped surfaces 21.

[0028] Core 2, as an example, has dimensions of 3.5 mm in the axial direction AX, 2.6 mm in the width direction WD, and 1.4 mm in the height direction HD.

[0029] As mentioned above, the four metal terminals 9 to 12 have the same or symmetrical shapes, so a common reference numeral is used for the common parts of each of the metal terminals 9 to 12.

[0030] Each of the metal terminals 9 to 12 is provided with a base portion 24, at which it is fixed to the outer end faces 18 of the flange portions 5 and 6, for example, via an adhesive. The metal terminals 9 to 12 may also be fixed to the flange portions 5 and 6 by crimping instead of via an adhesive. Each of the metal terminals 9 to 12 further includes a mounting portion 25 that extends along a high surface 20 after being bent from the base portion 24 and is connected to a mounting substrate (not shown), a wire connection portion 26 that extends along a low surface 22 and to which a wire 7 is connected, and a connecting portion 27 that extends along a stepped surface 21 and connects the mounting portion 25 and the wire connection portion 26.

[0031] The coil component 1 includes a top plate 31 that spans between the first flange portion 5 and the second flange portion 6 of the core 2. The top plate 31 contains a ceramic such as ferrite. The top plate 31 has a first main surface 33 facing the core 2 side, a second main surface 34 facing the opposite side of the first main surface 33, and a side surface 35 connecting the first main surface 33 and the second main surface 34. The side surface 35 consists of four planes that are connected to each other and give the circumferential surface of the top plate 31. Preferably, the ceramic included in the top plate 31 has a relative permeability in the range of 200 to 2000.

[0032] The top plate 31 is fixed to the core 2 via adhesive (not shown) with its first main surface 33 facing the top surfaces 16 of the first flange portion 5 and the second flange portion 6. The top plate 31 works in cooperation with the core 2 to form a closed magnetic circuit and acts to improve the inductance value of the coil component 1.

[0033] Figure 2 shows an enlarged cross-sectional view of a portion of the first flange 5 and a portion of the top plate 31 of the core 2 provided in the coil component 1. Figure 2 shows a cross-section obtained by cutting the coil component 1 shown in Figure 1 along a plane defined by a side extending in the axial direction AX and a side extending in the height direction HD.

[0034] As shown in Figure 2, the first flange portion 5 is illustrated in this disclosure. In this disclosure, the thickness TD of the first flange portion 5 and the second flange portion 6, which is the distance between the inner end face 17 and the outer end face 18, is always 0.4 mm or more and 0.7 mm or less.

[0035] Furthermore, as shown in Figure 2, a chamfered portion 36 is provided on the ridge line portion R where the first main surface 33 and the side surface 35 intersect on the top plate 31, in a range S1 of 0.06 mm or more and 0.20 mm or less measured from the side surface 35 in a direction perpendicular to the side surface 35, around the entire circumference of the first main surface 33. The chamfered portion 36 is defined by a uniform surface. However, a uniform surface here may not only be a perfectly flat surface, but may also include gentle irregularities or slopes.

[0036] More specifically, the chamfered portion 36 is further subjected to barrel polishing. As a result of this barrel polishing, the following shape is achieved. Figure 3 shows a further enlarged view of a part of the top plate 31 shown in Figure 2. In Figure 3, the cross-sectional outline of the top plate 31 before barrel polishing is shown by a solid line, and the cross-sectional outline of the top plate 31 after barrel polishing is shown by a dotted line.

[0037] Referring to Figure 3, after the top plate 31 has been formed but before barrel polishing, the top plate 31 has a chamfered portion 36 in the area S2 shown by the solid line. Next, when the top plate 31 is subjected to barrel polishing, the edge portion of the chamfered portion 36 is polished, and a first convex rounded shape 37 is given. In this disclosure, the barrel polishing conditions are set so that the first convex rounded shape 37 is given to a region S3 along the inner peripheral edge of the chamfered portion 36 with a width of 0.01 mm or more and 0.05 mm or less.

[0038] Furthermore, as a result of the barrel polishing process described above, a second convex curvature 38 is provided to the region along the outer edge of the chamfered portion 36.

[0039] As a result of this barrel polishing process, the top plate 31 is provided with chamfered portions 36 in a range S1 of 0.06 mm or more and 0.20 mm or less, measured from the side surface 35 in a direction perpendicular to the side surface 35, around the entire circumference of the first main surface 33. The chamfered portions 36 form a uniform surface.

[0040] The numerical limitation of 0.20 mm or less for the range S1 of the chamfered portion 36 described above was determined by experiments investigating how the inductance value of the coil component 1 changes when the range S1 of the chamfered portion 36 is changed.

[0041] In this experiment, when the thickness of the flange 5 is 0.66 mm and the range S1 is 0.15 mm and 0.20 mm, the inductance change rate is 1.00, and there is no substantial change in the inductance value. However, when the range S1 is 0.25 mm, the inductance change rate is 0.965, and when the range S1 is 0.30 mm, the inductance change rate is 0.89. From this result, it can be seen that if the range S1 is 0.20 mm or less, no substantial decrease in the inductance value is caused.

[0042] On the other hand, regarding the range S1 of the chamfered portion 36, the numerical limitation of 0.06 mm or more is obtained by actually measuring the lower limit value that can achieve chipping prevention of the top plate 31. It can be inferred that the provision of the first convex roundness 37 in the region S3 having a width of 0.01 mm or more and 0.05 mm or less along the inner peripheral edge of the chamfered portion 36 also effectively acts on this chipping prevention.

[0043] FIG. 4 is an enlarged cross-sectional view showing a part of a top plate 31a provided in a coil component according to a second embodiment of the present disclosure, before and after barrel polishing, similarly to the case of FIG. 3. In FIG. 4, elements corresponding to those shown in FIG. 3 are denoted by the same reference numerals, and duplicate descriptions are omitted.

[0044] Referring to FIG. 4, after molding the top plate 31a and before barrel polishing, the top plate 31a forms a chamfered portion 36a in a range S2 as shown by the solid line. The chamfered portion 36a has a stepped shape. Next, when the top plate 31a is subjected to barrel polishing, the edge portion of the chamfered portion 36a is polished, and a first convex roundness 37a is imparted. In the present disclosure, the barrel polishing conditions are set such that the first convex roundness 37a is imparted to the region S3 having a width of 0.01 mm or more and 0.05 mm or less along the inner peripheral edge of the chamfered portion 36a.

[0045] In addition, as a result of the above-mentioned barrel polishing, a second convex roundness 38a is imparted to the region along the outer peripheral edge of the chamfered portion 36a.

[0046] As a result of such barrel polishing, a chamfer 36a is provided on the top plate 31a over the entire circumference of the first main surface 33 in the range S1 of 0.06 mm or more and 0.20 mm or less as measured from the side surface 35 in the direction perpendicular to the side surface 35. The chamfer 36a forms a stepped surface.

[0047] The coil component according to the present disclosure has been described above with reference to the illustrated embodiments, but various other embodiments are possible within the scope of the present disclosure.

[0048] For example, the coil component to which the present disclosure is directed may be one that constitutes a single coil, one that constitutes a transformer, a balun, etc., other than one that constitutes a common mode choke coil as in the illustrated embodiment. Therefore, the number of wires can also be changed according to the function of the coil component, and accordingly, the number of metal terminals provided on each flange can also be changed.

[0049] Further, the metal terminals 9 to 12 are not necessarily made of a metal plate, but may be formed of a conductive film obtained by applying and baking silver paste, for example.

[0050] Further, the plurality of metal terminals 9 to 12 do not need to have the same shape as each other, nor do they need to be symmetrical. The plurality of metal terminals may have partially different shapes from each other, or may have completely different shapes.

[0051] Furthermore, in configuring the coil component according to the present disclosure, partial replacement or combination of configurations is possible between different embodiments described in this specification.

[0052] The present disclosure includes the following embodiments.

[0053] <1> A core having a winding core portion extending in the axial direction and a first flange portion and a second flange portion provided at a first end portion and a second end portion of the winding core portion that are opposite to each other in the axial direction, respectively; a top plate containing ceramic stretched between the first flange portion and the second flange portion; and at least one wire wound around the winding core portion, wherein each of the first flange portion and the second flange portion has a bottom surface facing the mounting substrate side when mounted, a top surface opposite to the bottom surface, an inner end surface connecting the bottom surface and the top surface, facing the winding core portion side and where the axial end portion of the winding core portion is located, and an outer end surface facing the opposite side of the inner end surface, and the thickness of each of the first flange portion and the second flange portion, which is the distance between the inner end surface and the outer end surface facing each other, is always 0.4 mm or more and 0.7 mm or less. The top plate has a first main surface facing the core, a second main surface facing the opposite side of the first main surface, and a side surface connecting the first main surface and the second main surface, and is fixed to the core with the first main surface facing the top surface of the first flange and the second flange, and a chamfered portion is provided on the ridge line portion where the first main surface and the side surface intersect on the top plate, in a range of 0.06 mm or more and 0.20 mm or less measured from the side surface in a direction perpendicular to the side surface, along the entire circumference of the first main surface, and a first convex rounded shape is provided in the region along the inner edge of the chamfered portion with a width of 0.01 mm or more and 0.05 mm or less.

[0054] <2> The coil component according to <1>, wherein a second convex curve is provided in the region along the outer edge of the chamfered portion.

[0055] <3> The coil component described in <2>, wherein the chamfered portion forms a uniform surface.

[0056] <4> The coil component according to <2>, wherein the chamfered portion forms a surface with a step.

[0057] 1 Coil component 2 Core 3 Winding core 5 First flange 6 Second flange 7, 8 Wire 9-12 Metal terminal 15 Bottom surface 16 Top surface 17 Inner end surface 18 Outer end surface 31, 31a Top plate 33 First main surface 34 Second main surface 35 Side surface 36, 36a Chamfered part 37, 37a First rounded edge 38, 38a Second rounded edge AX Axial direction TD Thickness

Claims

1. A core having a winding core portion extending in the axial direction and a first flange portion and a second flange portion provided at the first and second ends of the winding core portion that are opposite to each other in the axial direction; a top plate containing ceramic stretched between the first flange portion and the second flange portion; and at least one wire wound around the winding core portion, wherein each of the first flange portion and the second flange portion has a bottom surface facing the mounting substrate side when mounted, a top surface opposite to the bottom surface, an inner end surface connecting the bottom surface and the top surface, facing the winding core portion and where the axial end of the winding core portion is located, and an outer end surface facing opposite to the inner end surface, and the thickness of each of the first flange portion and the second flange portion, which is the distance between the inner end surface and the outer end surface facing each other, is always 0.4 mm or more and 0.7 mm or less. The top plate has a first main surface facing the core, a second main surface facing the opposite side of the first main surface, and a side surface connecting the first main surface and the second main surface, and is fixed to the core with the first main surface facing the top surface of the first flange and the second flange, and a chamfered portion is provided on the ridge line portion where the first main surface and the side surface intersect on the top plate, in a range of 0.06 mm or more and 0.20 mm or less measured from the side surface in a direction perpendicular to the side surface, along the entire circumference of the first main surface, and a first convex rounded shape is provided in the region along the inner edge of the chamfered portion with a width of 0.01 mm or more and 0.05 mm or less.

2. The coil component according to claim 1, wherein a second convex curve is provided in the region along the outer edge of the chamfered portion.

3. The coil component according to claim 2, wherein the chamfered portion forms a uniform surface.

4. The coil component according to claim 2, wherein the chamfered portion forms a surface having a step.

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