Coil components

Abstract

This invention provides a coil component with improved DC superposition characteristics. [Solution] A coil component 1 comprises a core 2 made of a magnetic material having a winding core 3 and a first flange 5 and a second flange 6 provided at opposite ends of the winding core 3 in the axial direction AX, respectively; a top plate 14 made of a magnetic material stretched between the first flange 5 and the second flange 6; and at least one wire 13 wound around the winding core 3. The top plate 14 is fixed to the core 2 with a gap G provided between it and the top surfaces 9 and 10 of the flanges 5 and 6, with an average dimension of 20 μm or more and 50 μm or less relative to the top surfaces 9 and 10; and when viewed in terms of the cross-sectional area along a plane passing through the center position of the core 2 in the axial direction AX and perpendicular to the axial direction AX, the ratio of (cross-sectional area of ​​the top plate) / (cross-sectional area of ​​the winding core) is 0.478 or more and 0.956 or less.

Description

Technical Field

[0001] The present disclosure relates to a coil component including a core having a core part around which a wire is wound, a first flange part and a second flange part provided at each end of the core part, and a top plate spanned between the first flange part and the second flange part.

Background Art

[0002] As a technology of interest to the present disclosure, for example, Japanese Patent Application Laid-Open No. 2018-107248 (Patent Document 1) describes a coil component including a core having a core part around which a wire is wound, a first flange part and a second flange part provided at each end of the core part, and a top plate spanned between the first flange part and the second flange part. In the coil component described in Patent Document 1, in order to obtain good DC superposition characteristics, the top plate is fixed to the core with a gap provided with respect to the first flange part and the second flange part. The gap is formed, for example, by providing small protrusions on the part of the top plate facing the flange part. By providing such a gap, magnetic saturation that may occur in the closed magnetic circuit structure formed by the core and the top plate is suppressed, and the DC superposition characteristics of the coil component can be improved.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As mentioned above, a larger gap provides a greater effect in suppressing magnetic saturation, but if it is too large, the inductance improvement effect from the top plate becomes almost negligible. Furthermore, even with a gap, if the cross-sectional area ratio of the core forming the closed magnetic circuit and the top plate is unsuitable, one of them will preferentially undergo magnetic saturation, leading to a deterioration of the DC superposition characteristics. Therefore, there are limitations to improving DC superposition characteristics solely through the use of a gap.

[0005] Therefore, the purpose of this disclosure is to provide a coil component with improved DC superposition characteristics without relying solely on the gap. [Means for solving the problem]

[0006] This disclosure is directed to a coil component comprising: a core made of a magnetic material having an axially extending core portion and a first flange portion and a second flange portion provided at the first and second ends of the core portion that are opposite to each other in the axial direction; a top plate made of a magnetic material stretched between the first flange portion and the second flange portion; and at least one wire wound around the core portion.

[0007] Each of the first and second flanges has a bottom surface that faces the mounting substrate side during mounting, and a top surface opposite the bottom surface.

[0008] The coil component according to this disclosure is characterized in that the top plate is fixed to the core with a gap that is opposite to the top surfaces of the first flange and the second flange and has an average dimension of 20 μm or more and 50 μm or less relative to the top surface, and when viewed in terms of the cross-sectional area along a plane that passes through the center position of the core in the axial direction and is perpendicular to the axial direction, the ratio of (cross-sectional area of ​​the top plate) / (cross-sectional area of ​​the winding core) is 0.478 or more and 0.956 or less. [Effects of the Invention]

[0009] According to this disclosure, magnetic saturation is suppressed by first providing a gap between the top plate and the flange. Here, by setting the average dimension of the gap to a range of 20 μm or more and 50 μm or less, the rate of change of the inductance value is kept within ±20% of the inductance value when the average dimension of the gap is 30 μm. It can be suppressed.

[0010] Furthermore, according to this disclosure, by setting the average gap dimension to a range of 20 μm or more and 50 μm or less, and the ratio of (cross-sectional area of ​​the top plate) / (cross-sectional area of ​​the winding core) to 0.478 or more and 0.956 or less, the current value at which the inductance value decreases by 30% can be set to 664 mA or more, thereby improving the DC superposition characteristics of the coil component. [Brief explanation of the drawing]

[0011] [Figure 1] This is a front view showing the appearance of a coil component 1 according to one embodiment of the present disclosure. [Figure 2] This is a schematic, enlarged cross-sectional view showing the joint between the first flange portion 5 and the top plate 14 in the coil component 1 shown in Figure 1. [Figure 3] This diagram illustrates the average dimension of the gap G between the first flange portion 5 and the top plate 14. [Modes for carrying out the invention]

[0012] A coil component 1 according to one embodiment of the present disclosure will be described with reference to Figures 1 to 3.

[0013] As shown in Figure 1, the coil component 1 comprises a core 2 made of a magnetic material such as ferrite, like Ni-Zn ferrite, or a resin containing metallic magnetic powder. As the ferrite, one with a relative permeability of, for example, 200 to 1000 can be used. As the resin containing metallic magnetic powder, one with a relative permeability of 20 to 60 can be used. 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, which are opposite to each other in the axial direction AX. The cross-sectional shape of the winding core portion 3 is, for example, a square shape, but it may also be a polygon such as a hexagon, a circle, an ellipse, or a combination thereof.

[0014] The first flange portion 5 and the second flange portion 6 each have a first bottom surface 7 and a second bottom surface 8 that are oriented toward the mounting substrate (not shown) during mounting, and a first top surface 9 and a second top surface 10 opposite to the first bottom surface 7 and the second bottom surface 8, respectively.

[0015] 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 dipping or printing a conductive paste containing conductive metal powder such as Ag powder, then baking it, and subsequently applying Cu plating, Ni plating, and Sn plating. Alternatively, the terminal electrodes 11 and 12 may be provided by attaching terminal members made of conductive metal plates to the flange portions 5 and 6.

[0016] At least one wire 13 is wound around the core 3. The wire 13 comprises 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 core 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 connected to the second terminal electrode 12. For connection between the terminal electrodes 11 and 12 and the wire 13, for example, thermocompression welding, ultrasonic welding, or laser welding may be applied. The number of turns of the wire 13 on the core 3 is arbitrarily selected according to the required characteristics. The wire 13 may be multi-layered if necessary.

[0017] The coil component 1 includes a top plate 14 that spans between the first flange portion 5 and the second flange portion 6. The top plate 14 is made of a magnetic material such as ferrite, like Ni-Zn ferrite, or a resin containing metallic magnetic powder. When both the core 2 and the top plate 14 are made of magnetic material, the top plate 14 cooperates with the core 2 to form a closed magnetic circuit.

[0018] The top plate 14 is fixed to the core 2 facing the top surfaces 9 and 10 of the first flange portion 5 and the second flange portion 6, respectively, with a gap G between the top surfaces 9 and 10. The preferred average dimension of the gap G is determined to be 20 μm or more and 50 μm or less, based on simulation results described later. The "average dimension" of the gap G will be described later with reference to Figure 3. A non-magnetic material is placed in the gap G. Typically, an adhesive 15 is used as the non-magnetic material. The adhesive 15 includes, for example, a thermosetting resin such as an epoxy resin. To improve thermal shock resistance, filler particles 16 made of a non-magnetic material such as silica are added to the adhesive 15, as shown in Figure 2.

[0019] Figure 2 is a schematic cross-sectional view showing an enlarged view of the joint between the first flange 5 and the top plate 14. Note that the joint between the second flange 6 and the top plate 14 has substantially the same structure as the joint between the first flange 5 and the top plate 14 shown in Figure 2; therefore, the explanation of the joint between the first flange 5 and the top plate 14 will be used for this joint.

[0020] In addition to improving the thermal shock resistance described above, the filler particles 16 also have the function of securing the gap G. As shown in FIG. 2, the filler particles 16 include those of various particle sizes. Among the filler particles 16 of various particle sizes, the filler particle 16M with the largest particle size acts to define the dimension of the gap G. Thus, if the dimension of the gap G is defined by the filler particle 16M with the largest particle size, the following advantages can be achieved.

[0021] As described in Patent Document 1, if a gap is defined by small protrusions provided at the portion of the top plate facing the flange portion, the tip of the protrusion comes into direct contact with or is in a very close state to the flange portion, so local magnetic saturation is likely to occur at the protrusion portion. This causes deterioration of the DC superposition characteristics. On the other hand, if, as in this embodiment, there are no protrusions and the dimension of the gap G is defined by the filler particle 16M with the largest particle size made of a non-magnetic material, deterioration of the DC superposition characteristics can be suppressed.

[0022] Previously, regarding the dimension of the gap G, the expression "average dimension" was used, and the "average dimension" was to be described with reference to FIG. 3. FIG. 3 is a diagram for explaining the average dimension of the gap G between the first flange portion 5 and the top plate 14. The same explanation can also be applied to the average dimension of the gap G between the second flange portion 6 and the top plate 14.

[0023] As shown in FIGS. 3(A) to (C), a chamfer portion B may be provided at the ridge line portion of the top plate 14 to prevent the adhesive 15 from overflowing. FIG. 3(A) shows a state where the outer periphery of the top plate 14 coincides with the outer periphery of the top surface 9 of the flange portion 5, FIG. 3(B) shows a state where the outer periphery of the top plate 14 is outside the outer periphery of the top surface 9 of the flange portion 5, and FIG. 3(C) shows a state where the outer periphery of the top plate 14 is inside the outer periphery of the top surface 9 of the flange portion 5. In the state of FIG. 3(B), the dimension of the gap G is substantially uniform throughout the area, but in the states of FIGS. 3(A) and (C), the dimension of the gap G is larger at the peripheral portion than at the central portion.

[0024] In the cases shown in Figures 3(A) to 3(C), there is a difference in interpretation regarding how to measure the dimensions of the gap G: whether to measure only the portion without chamfered portion B, or to also consider the dimensions of chamfered portion B. Therefore, in this specification, the dimension of the gap G is defined as follows and expressed as the "average dimension".

[0025] Let S be the area of ​​the surface where the top surface 9 of the first flange 5 and the top plate 14 overlap, as viewed from a direction perpendicular to the top surface 9. Let V be the volume between the flange 5 and the top plate 14 within that surface. The "average dimension" of the gap G is defined as V / S, which is set to be between 20 μm and 50 μm.

[0026] Furthermore, chamfered portions may also be formed in core 2, for example, by barrel polishing after molding. Even in this case, the average dimension of gap G can be determined according to the definition described above.

[0027] In this disclosure, as described above, in order to suppress magnetic saturation and reduce the rate of change of the inductance value, the top plate 14 is fixed to the core 2 with a gap G provided between it and the top surfaces 9 and 10 of the first flange portion 5 and the second flange portion 6, and with an average dimension of 20 μm or more and 50 μm or less relative to the top surfaces 9 and 10. Furthermore, in order to improve the DC superposition characteristics, the ratio of (cross-sectional area of ​​top plate 14) / (cross-sectional area of ​​winding core portion 3) is set to 0.478 or more and 0.956 or less when viewed as the cross-sectional area along a plane that passes through the center position in the axial direction AX of the core 2 and is perpendicular to the axial direction AX. These numerical ranges were obtained from the following simulation results.

[0028] The coil components used in this simulation had dimensions of 2.0 mm in the length direction (axial direction AX) of the core, 1.2 mm in the width direction (direction perpendicular to the plane of the paper in Figure 1), and 1.3 mm in the height direction (vertical direction in Figure 1). The width direction of the winding core was 0.74 mm, and the height direction was 0.68 mm. The axial direction AX of the top plate was 2.0 mm, and the width direction was 1.2 mm. The core and top plate were made of ferrite with the same magnetic permeability.

[0029] In these coil components, the average gap size was varied from 15 μm, 20 μm, 30 μm, 45 μm, 50 μm, and 60 μm, while the height dimension of the top plate (vertical direction in Figure 1) was varied from 0.15 mm to 0.45 mm. This changed the ratio of (cross-sectional area of ​​top plate) to (cross-sectional area of ​​winding core) to 0.359, 0.478, 0.598, 0.717, 0.836, 0.956, and 1.074, and the inductance value and DC superposition characteristics of the coil component were determined.

[0030] Table 1 shows the percentage change in inductance value [%] relative to the inductance value when the average gap dimension in the coil component is 30 μm.

[0031] [Table 1]

[0032] As can be seen from Table 1, the rate of change in inductance value is kept within ±20% in the range where the average gap dimension is between 20 μm and 50 μm.

[0033] Table 2 shows the current values ​​[mA] when the inductance value of a coil component decreases by 30%. The current values ​​shown in Table 2 are the current values ​​when the inductance value decreases by 30% compared to the initial inductance value without superimposed current.

[0034] [Table 2]

[0035] As can be seen from Table 2, when the average gap dimension is in the range of 20 μm or more and 50 μm or less, and the cross-sectional area ratio is in the range of 0.478 or more and 0.956 or less, a current value of 664 mA or more is obtained when the inductance value decreases by 30%, indicating good DC superposition characteristics. Furthermore, when the cross-sectional area ratio is in the range of 0.598 or more and 0.956 or less, a current value of 758 mA or more is obtained when the inductance value decreases by 30%, indicating even better DC superposition characteristics.

[0036] In Tables 1 and 2, to clearly indicate the preferred range, the range where the average gap dimension is 20 μm or more and 50 μm or less, and the cross-sectional area ratio is 0.478 or more and 0.956 or less, is enclosed by a thick dotted line, and the range where the average gap dimension is 20 μm or more and 50 μm or less, and the cross-sectional area ratio is 0.598 or more and 0.956 or less, is enclosed by a thick dashed line.

[0037] Furthermore, as mentioned above, the upper limit of the cross-sectional area ratio is 0.956, which is less than 1.000. In other words, the cross-sectional area of ​​the top plate is smaller than the cross-sectional area of ​​the winding core. This is because, as long as a gap exists, the magnetic flux density on the top plate side will inevitably be lower than that on the winding core side, and good DC superposition characteristics can be ensured even if the cross-sectional area of ​​the top plate is smaller than that of the winding core. In other words, even if the cross-sectional area of ​​the top plate is larger than that of the winding core, it will not produce a favorable difference in terms of DC superposition characteristics.

[0038] The above description has been made in relation to an illustrated embodiment of the coil component relating to this disclosure, but various other modifications are possible within the scope of this disclosure.

[0039] For example, instead of using an adhesive 15 as a non-magnetic material in the gap G, a sheet made of a non-magnetic material may be sandwiched between the top surfaces 9 and 10 of the first flange portion 5 and the second flange portion 6 and the top plate 14, thereby creating the gap G.

[0040] Furthermore, the dimensions of each part of the coil component used in the simulation described above are merely examples, and the dimensions of each part of the coil component can be arbitrarily changed as needed. For example, in the simulation, the dimensions of the coil component core were 2.0 mm in the length direction and 1.2 mm in the width direction, but for example, the dimensions could be 3.2 mm in the length direction and 2.5 mm in the width direction, or 4.5 mm in the length direction and 3.2 mm in the width direction.

[0041] Furthermore, although the illustrated embodiment shows a coil component constituting a single coil, the coil component to which this disclosure is directed may also constitute a common mode choke coil, a transformer, a balun, and the like. Accordingly, the number of wires may be changed according to the function of the coil component, and the number of terminal electrodes provided on each flange may also be changed accordingly.

[0042] Furthermore, in constructing the coil component relating to this disclosure, partial substitution or combination of configurations is possible between the different embodiments described in this specification.

[0043] This disclosure includes the following embodiments:

[0044] <1> A core made of a magnetic material 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 made of a magnetic material is placed between the first flange portion and the second flange portion, The aforementioned core is wound with at least one wire, Equipped with, Each of the first flange portion and the second flange portion has a bottom surface that faces the mounting substrate side during mounting, and a top surface opposite to the bottom surface, The top plate is fixed to the core with a gap provided between it and the top surfaces of the first flange and the second flange, with an average dimension of 20 μm or more and 50 μm or less relative to the top surface. When viewed along the cross-sectional area of ​​the core passing through its axial center and perpendicular to the axial direction, the ratio of (cross-sectional area of ​​the top plate) / (cross-sectional area of ​​the winding core) is 0.478 or more and 0.956 or less. Coil components.

[0045] <2> The ratio of (cross-sectional area of ​​the top plate) / (cross-sectional area of ​​the winding core) is 0.598 or more and 0.956 or less. <1> The coil component described above.

[0046] <3> The gap further comprises a non-magnetic material placed therein. <1> or <2> The coil component described above.

[0047] <4> The nonmagnetic material placed in the gap includes an adhesive. <3> The coil component described above.

[0048] <5> The adhesive includes filler particles made of a non-magnetic material to secure the gap. <4> The coil component described above.

[0049] <6> The filler particles comprise filler particles of various particle sizes, and the dimensions of the gap are substantially defined by the largest particle size of the filler particles. <5> The coil component described above. [Explanation of Symbols]

[0050] 1. Coil component 2 cores 3. Core section 5,6 Guard section 7,8 Base 9,10 Top surface 11,12 terminal electrode 13 wires 14 Top plate 15 Adhesives 16 Filler particles 16M maximum particle size with filler particles AX Axial direction G Gap

Claims

1. A core made of a magnetic material 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 made of a magnetic material is placed between the first flange portion and the second flange portion, The aforementioned core is wound with at least one wire, Equipped with, Each of the first flange portion and the second flange portion has a bottom surface that faces the mounting substrate side during mounting, and a top surface opposite to the bottom surface, The top plate is fixed to the core with a gap provided between it and the top surfaces of the first flange and the second flange, with an average dimension of 20 μm or more and 50 μm or less relative to the top surface. When viewed along the cross-sectional area of ​​the core passing through its axial center and perpendicular to the axial direction, the ratio of (cross-sectional area of ​​the top plate) / (cross-sectional area of ​​the winding core) is 0.478 or more and 0.956 or less. Coil components.

2. The coil component according to claim 1, wherein the ratio of (cross-sectional area of ​​the top plate) / (cross-sectional area of ​​the winding core) is 0.598 or more and 0.956 or less.

3. The coil component according to claim 1, further comprising a non-magnetic material disposed in the gap.

4. The coil component according to claim 3, wherein the nonmagnetic material placed in the gap includes an adhesive.

5. The coil component according to claim 4, wherein the adhesive includes filler particles made of a non-magnetic material for securing the gap.

6. The coil component according to claim 5, wherein the filler particles comprise filler particles of various particle sizes, and the dimensions of the gap are substantially defined by the filler particles of the largest particle size.

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