Coil component

Abstract

The present invention provides a coil component which does not readily become filled with resin and which improves insulation resistance. A coil component 1 according to the present disclosure comprises: a magnetic body part BB containing first metal magnetic particles MP1 and a resin; an element body 10 having coils C1, C2 embedded in the magnetic body part BB; and an external electrode 20 provided on a mounting surface of the element body 10 and connected to the coils C1, C2. The coils C1, C2 include a first coil C1 and a second coil C2. The first coil C1 and the second coil C2 are each formed by means of a coil conductor CL1 and are arranged to face each other. An insulating layer IL containing second metal magnetic particles MP2 is disposed in at least a portion along the mutually facing surfaces of the first coil C1 and the second coil C2. The average particle size of the second metal magnetic particles MP2 is smaller than the average particle size of the first metal magnetic particles MP1. In a plan view, the lateral surface of the insulating layer IL is located farther inward than the lateral surface of the element body 10.

Description

Coil parts

[0001] The present disclosure relates to a coil component.

[0002] Patent Document 1 discloses a magnetically coupled coil component having a pair of coil units (a first coil conductor and a second coil conductor) that are magnetically coupled to each other.

[0003] Japanese Patent Application Laid-Open No. 2019-067883

[0004] In response to the recent demand for miniaturization of devices, if the coil component having a set of coil units (first coil conductor and second coil conductor) disclosed in Patent Document 1 is miniaturized, a potential difference may occur between the two coil conductors, potentially causing a short circuit.

[0005] In view of the above, an object of the present disclosure is to provide a coil component that improves the insulation resistance between two coil conductors.

[0006] The coil component of the present disclosure comprises: a magnetic body containing first metal magnetic particles and a resin; and a base body having a coil embedded in the magnetic body; and an external electrode provided on the mounting surface of the base body and connected to the coil, wherein the coil includes a first coil and a second coil, the first coil and the second coil are each formed from a coil conductor and arranged opposite each other, an insulating layer containing second metal magnetic particles is arranged along at least a portion of the opposing surface between the first coil and the second coil, the average particle size of the second metal magnetic particles is smaller than the average particle size of the first metal magnetic particles, and in a planar view, the side of the insulating layer is located inside the side of the base body.

[0007] According to the coil component of the present disclosure, resin filling from the outside is difficult, and insulation resistance can be improved.

[0008] FIG. 1 is a perspective view of a coil component according to the present disclosure. FIG. 2 is an exploded perspective view of a coil component according to the present disclosure. FIG. 3 is a schematic cross-sectional view of a coil component according to a first embodiment, taken along the III-III cross section of FIG. 2. FIG. 4 is an enlarged cross-sectional view of the dashed line area in FIG. 3. FIG. 5 is a schematic cross-sectional view of a coil component according to a second embodiment. FIG. 6 is a cross-sectional view of the VI-VI cross section of FIG. 5. FIG. 7 is a schematic cross-sectional view of a coil component according to a third embodiment. FIG. 8 is a cross-sectional view of the VIII-VIII cross section of FIG. 7. FIG. 9 is an enlarged cross-sectional view of the dashed line area in FIG. 7. FIG. 10 is an enlarged cross-sectional view of a coil component according to a modified example of the third embodiment. FIG. 11 is a schematic cross-sectional view of a coil component according to a fourth embodiment. FIG. 12 is an SEM photograph of the coil component according to the fourth embodiment. FIG. 13 is a schematic cross-sectional view of a coil component according to a comparative example. FIG. 14 is a table showing the results of a demonstration test on the coil component.

[0009] The coil component of the present disclosure will be described in detail below. While the description will be made with reference to drawings as necessary, the contents shown in the drawings are merely shown schematically and exemplarily to facilitate understanding of the present disclosure, and the appearance, dimensional ratio, etc. may differ from the actual product. The drawings shown below are schematic diagrams, and the dimensions, aspect ratio, etc. may differ from those of the actual product.

[0010] In this specification, terms indicating the relationship between elements (e.g., "parallel," "orthogonal," etc.) and terms indicating the shape of elements not only refer to the strict literal form, but also refer to a range of substantial equivalence, for example, a range including a difference of about a few percent. Note that in this specification, the direction in which the magnetic layers and coil conductors constituting the element body are stacked is referred to as the "stacking direction." Furthermore, a plan view refers to a plan view of the element body as seen from the top (height direction).

[0011] <Description of Coil Component of First Embodiment> A coil component 1 of the first embodiment will be described below with reference to Figures 1 to 4. The coil component 1 of the first embodiment includes an element body 10 and external electrodes 20 provided on the mounting surface of the element body 10.

[0012] [Element Body] The element body 10 has, for example, a hexahedral shape having six sides. As an example, it may have a rectangular parallelepiped shape or a substantially rectangular parallelepiped shape. The corners and ridges of the element body 10 may be rounded. A corner is a portion where three sides of the element body 10 intersect, and a ridge is a portion where two sides of the element body 10 intersect.

[0013] 1, the long side direction, short side direction, and height direction of the coil component 1 and the element body 10 are respectively indicated as L direction, W direction, and T direction. The long side direction L, the short side direction W, and the height direction T are perpendicular to each other.

[0014] 1 has a first main surface 11 and a second main surface 12 that face each other in the height direction T, a first end surface 13 and a second end surface 14 that face each other in the long side direction L, and a first side surface 15 and a second side surface 16 that face each other in the short side direction W. In the example shown in Fig. 1, a first external electrode 21, a second external electrode 22, a third external electrode 23, and a fourth external electrode 24 are formed on the first main surface 11 of the element body 10, and the first main surface 11 of the element body 10 corresponds to the mounting surface of the coil component 1 (the bottom surface of the element body).

[0015] 3 and 4, the element body 10 is provided with at least a magnetic body part BB containing first metal magnetic particles MP1 and a resin (not shown), coils (first coil C1 and second coil C2) embedded in the magnetic body part BB, and an insulating layer IL provided between the two coils. Note that the number of coils provided inside the element body 10 may be three or more.

[0016] To construct such an element body 10, the element body 10 is formed by stacking multilayer groups G1 to G8 as shown in Figure 2. The first external electrode 21 to the fourth external electrode 24 are formed below the multilayer group G8. Note that the boundaries between the layers in the layered structure of the element body 10 may disappear. Each of the multilayer groups G1 to G8 may be stacked multiple times to achieve the desired thickness.

[0017] The lamination group G1 has a metal magnetic layer ML that constitutes the magnetic body part BB (see FIG. 3), and constitutes the second main surface 12 of the element body 10 (see FIG. 1).

[0018] The multilayer group G2 and the multilayer group G3 are provided to configure the second coil C2 (see FIG. 3). That is, the coil conductor CL2 is laminated to configure the second coil C2. The multilayer groups G2 and G3 of the present disclosure may each be configured by laminating multiple layers.

[0019] One end of the second coil C2 is provided with a third through-hole conductor TH3 electrically connected to the third external electrode 23, and the other end of the second coil C2 is provided with a fourth through-hole conductor TH4 electrically connected to the fourth external electrode 24. A metal magnetic layer ML constituting the magnetic body part BB (see FIG. 3) is arranged around the coil conductor CL2, the third through-hole conductor TH3, and the fourth through-hole conductor TH4.

[0020] The multilayer group G4 is a multilayer group provided between the first coil C1 and the second coil C2 (see FIG. 3 ), and includes an insulating layer IL corresponding to the coil conductors CL1 and CL2 of the first coil C1 and the second coil C2. Details of the insulating layer IL will be described later. The multilayer group G4 also includes a third through-hole conductor TH3 and a fourth through-hole conductor TH4. Metal magnetic layers ML constituting the magnetic body portion BB (see FIG. 3 ) are disposed around the insulating layer IL, the third through-hole conductor TH3, and the fourth through-hole conductor TH4.

[0021] The multilayer group G5 and the multilayer group G6 are provided to configure the first coil C1 (see FIG. 3). That is, the coil conductor CL1 is laminated to configure the first coil C1. The multilayer group G5 and the multilayer group G6 of the present disclosure may each be configured by laminating multiple layers.

[0022] One end of the first coil C1 is provided with a first through-hole conductor TH1 electrically connected to the first external electrode 21, and the other end of the first coil C1 is provided with a second through-hole conductor TH2 electrically connected to the second external electrode 22. A metal magnetic layer ML that constitutes the magnetic body part BB (see FIG. 3) is arranged around the coil conductor CL1 and the first through-hole conductors TH1 to TH4.

[0023] The multilayer group G7 and the multilayer group G8 are provided with first through-hole conductors TH1 to 4th through-hole conductors TH4 corresponding to the arrangement of the first external electrodes 21 to 4th external electrodes 24. A metal magnetic layer ML is arranged around the first through-hole conductors TH1 to 4th through-hole conductors TH4. As shown in FIG. 2 , by making the planar area of ​​the first through-hole conductors TH1 to 4th through-hole conductors TH4 of the multilayer group G8 larger than the planar area of ​​the first through-hole conductors TH1 to 4th through-hole conductors TH4 of the multilayer group G7, the alignment of the through-hole conductors can be facilitated.

[0024] As described above, when the element body 10 has a layered structure including the multilayer groups G1 to G8, the degree of freedom in designing the coil component 1 is increased. For example, when manufacturing a coil component 1 including the first external electrode 21 to the fourth external electrode 24 on the bottom surface (first main surface 11) of the element body 10, it becomes easier to draw the coil conductor CL to the bottom surface side using a through-hole conductor. Note that the layered structure including the above-mentioned layered groups G1 to G8 may be stacked from the second main surface 12 side or the first main surface 11 side of the element body 10. Furthermore, the material constituting the through-hole conductor layer TL and / or the via conductor may be repeatedly printed by, for example, screen printing until the via conductor reaches the desired thickness, or may be formed by sputtering, inkjet printing, or other known methods.

[0025] As described above, the element body 10 includes at least the magnetic body BB containing first metal magnetic particles MP1 and a resin (not shown), the coils (first coil C1 and second coil C2) embedded in the magnetic body BB, and the insulating layer IL. Each element constituting the element body 10 will be described in detail below.

[0026] -Magnetic Body Part- The magnetic body part BB, which is formed by laminating metal magnetic layers ML, may include first metal magnetic particles MP1 made of a metal magnetic material. The first metal magnetic particles MP1 may contain Fe and / or Si. More specifically, they may be Fe particles or Fe alloy particles. Examples of Fe alloys include Fe-Si alloys, Fe-Cr alloys, Fe-Si-Cr alloys, Fe-Si-Al alloys, Fe-Si-B-P-Cu-C alloys, and Fe-Si-B-Nb-Cu alloys. The first metal magnetic particles MP1 may also contain impurities such as Cr, Mn, Cu, Ni, P, S, or Co that are not intended during manufacturing. The first metal magnetic particles MP1 may also be contained in a magnetic paste. Therefore, the first metal magnetic particles MP1 may contain elements (for example, Cr, Al, Li, Zn, Zr) that are more easily oxidized than the Fe added when the magnetic paste is prepared.

[0027] The surfaces of the first metal magnetic particles MP1 described above may be covered with an insulating coating IC1 (see FIG. 4). Covering the surfaces of the first metal magnetic particles MP1 with the insulating coating IC1 enhances the insulation between the first metal magnetic particles MP1, improving the withstand voltage of the inductor and suppressing eddy currents generated in the first metal magnetic particles MP1. Methods for forming the insulating coating IC1 on the surfaces of the first metal magnetic particles MP1 include the sol-gel method and the mechanochemical method. The insulating coating IC1 may be made of an oxide of P, Si, or the like, zinc phosphate, or manganese phosphate. The insulating coating IC1 may also be an oxide film formed by oxidizing the surfaces of the first metal magnetic particles MP1 with oxygen in the atmosphere, or an oxide film of an element more easily oxidized than Fe. The thickness of the insulating coating IC1 is preferably 1 nm or more and 50 nm or less, more preferably 1 nm or more and 30 nm or less, and even more preferably 1 nm or more and 20 nm or less. For example, a cross section obtained by polishing an inductor sample is photographed with a scanning electron microscope (SEM), and the thickness of the insulating coating IC1 covering the surface of the first metal magnetic particle MP1 can be measured from the obtained SEM photograph.

[0028] The average particle size of the first metal magnetic particles MP1 in the magnetic body BB is larger than the average particle size of the second metal magnetic particles MP2 contained in the insulating layer IL between the coils (described later), preferably 5 μm to 50 μm, more preferably 5 μm to 20 μm, and even more preferably 5 μm to 10 μm. The average particle size of the first metal magnetic particles MP1 in the magnetic body BB can be measured using the procedure described below. An inductor sample is cut to obtain a cross-section. Specifically, the sample cross-section is obtained by cutting through the center of the element body 10 perpendicular to the mounting surface and end surface of the coil component. Multiple (e.g., five) regions (e.g., 130 μm x 100 μm) of the obtained cross-section other than the insulating layer IL are photographed using an SEM. The obtained SEM images are analyzed using image analysis software (e.g., image analysis software WinROOF2021 (manufactured by Mitani Corporation)) to determine the circle-equivalent diameter of the metal magnetic particles. The average of the obtained circle-equivalent diameters is taken as the average particle size of the metal magnetic particles.

[0029] When forming the element body 10, a heat treatment may be performed. In this case, the first metal magnetic particles MP1 contained in the element body 10 have an oxide film (insulating coating IC1) on their surfaces. This oxide film originates from the first metal magnetic particles MP1 and is formed by the heat treatment. In the element body 10, adjacent first metal magnetic particles MP1 are joined to each other via the oxide film to form the magnetic body part BB.

[0030] In order to further improve the strength of the element body 10, the element body 10 may be impregnated with a resin material after firing the element body 10. As an example of a resin that increases the strength of the element body, an epoxy resin and / or a phenol resin and / or a silicone resin may be used.

[0031] Coils (first coil C1 and second coil C2) formed by stacking coil conductors CL1 and CL2 may have a winding axis in the stacking direction. As described above, adjacent coil conductors in the stacking direction may be connected via via conductors. In the embodiment shown in FIG. 2, the first coil C1 (see FIG. 3) is formed by the stacking group G5 and the stacking group G6. The second coil C2 (see FIG. 3) is formed by the stacking group G2 and the stacking group G3.

[0032] The thickness of the coil conductors CL1 and CL2 may be the same or different in each lamination group. The coil conductors CL1 and CL2 may contain Ag as an example of a material, and may further contain metal conductors such as Cu and / or Pd. The coil conductors CL1 and CL2 may be formed, for example, by printing a conductive paste on the metal magnetic layer ML.

[0033] 2, the first coil C1 and the second coil C2 are formed by coil conductors CL1 and CL2, respectively, and are arranged opposite each other. Specifically, the second coil C2 is arranged above the first coil C1 in the stacking direction, so that the first coil C1 and the second coil C2 are arranged opposite each other.

[0034] Insulating Layer As described above, the insulating layer IL is configured by the laminate group G4 in FIG. 2 . More specifically, the insulating layer IL is disposed along at least a portion of the opposing surface between the first coil C1 and the second coil C2. As used herein, "disposed along at least a portion of the opposing surface between the first coil C1 and the second coil C2" refers to the insulating layer IL being disposed over the entire area where the upper surface of the first coil C1 and the lower surface of the second coil C2 overlap in a planar perspective view, as well as the insulating layer IL being disposed in a portion of the area where the upper surface of the first coil C1 and the lower surface of the second coil C2 overlap. Note that the insulating layer IL may be disposed in a position where the first coil C1 and the second coil C2 do not strictly face each other, as long as it is disposed along at least a portion of the opposing surface between the first coil C1 and the second coil C2. As an example, the insulating layer IL may be provided in a loop shape, as in the laminate group G4 in FIG. 2 .

[0035] The insulating layer IL may include second metal magnetic particles MP2 (see FIG. 4). The second metal magnetic particles MP2 may use the same metal magnetic material as the first metal magnetic particles MP1, or may use a metal magnetic material different from that of the first metal magnetic particles MP1. The surfaces of the second metal magnetic particles MP2 may be covered with an insulating coating IC2.

[0036] The average particle size of the second metal magnetic particles MP2 used in the insulating layer IL is smaller than that of the first metal magnetic particles MP1. The average particle size of the second metal magnetic particles MP2 can be measured using the procedure described below. An inductor sample is cut to obtain a cross-section. Specifically, the sample cross-section is obtained by cutting through the center of the element body 10 perpendicular to the mounting surface and end surface of the coil component. For the obtained cross-section, multiple (e.g., five) regions (e.g., 130 μm × 100 μm) of the insulating layer IL are photographed using an SEM. The obtained SEM images are analyzed using image analysis software (e.g., image analysis software WinROOF2021 (manufactured by Mitani Corporation)) to determine the circular equivalent diameter of the metal magnetic particles. The average of the obtained circular equivalent diameters is used as the average particle size of the metal magnetic particles. Generally, small-diameter particles coated with an insulating coating have more contact points with neighboring particles than large-diameter particles coated with an insulating coating, thereby increasing contact resistance and improving insulation resistance. Therefore, by making the average particle size of the second metal magnetic particles MP2 used in the insulating layer IL smaller than the average particle size of the first metal magnetic particles MP1 used in the magnetic body part BB, the insulation resistance of the insulating layer IL can be improved.

[0037] Generally, small-diameter particles are more susceptible to capillary action than large-diameter particles. Therefore, if small-diameter particles are exposed from the element body 10 during resin impregnation after firing the element body to improve its strength, resin can penetrate into the element body 10 from the outside through the small-diameter particles. If resin penetrates into the element body 10 from the outside, the heat from the heat treatment (e.g., reflow) performed when mounting the coil component on a substrate can thermally decompose the resin, generating reducing gas. This reducing gas can reduce the insulating coating IC2 (oxide film) covering the second metal magnetic particles MP2, potentially causing a deterioration in insulation resistance. Small-diameter particles, in particular, have a high resin filling rate due to capillary action and are therefore more susceptible to insulation resistance degradation.

[0038] Therefore, in a plan view, the insulating layer IL of the coil component 1 of the present disclosure has its side surface located inside the side surface of the element body 10. In other words, the insulating layer IL is provided so as not to be exposed from the element body 10. By providing the insulating layer IL in this manner, the coil component 1 of the present disclosure can be made less susceptible to external resin impregnation into the insulating layer IL, even when resin material is impregnated after firing the element body to improve element body strength. As a result, even when the coil component 1 of the present disclosure is subjected to a heat treatment (e.g., reflow) performed when mounting the coil component 1 on a substrate, reduction of the oxide film covering the metal magnetic particles is less likely to occur, making it less likely to cause deterioration of insulation resistance. Therefore, a coil component with improved insulation resistance can be provided.

[0039] The arrangement of the insulating layer IL may be more detailed. In a plan view, the insulating layer IL may be disposed so as not to protrude from the first coil C1 and the second coil C2. Specifically, the outer surface of the insulating layer IL may be disposed inside a line extending from the outer surface of the first coil C1 to the outer surface of the second coil C2 in the stacking direction. More specifically, the outermost position of the insulating layer IL may be disposed inside a line extending from the outermost position of the first coil C1 to the outermost position of the second coil C2. This insulating layer IL can more effectively prevent resin from being impregnated into the insulating layer IL from the outside and can ensure the insulating properties between the first coil C1 and the second coil C2, compared to when the insulating layer IL protrudes from the first coil C1 and the second coil C2.

[0040] In a preferred embodiment of the insulating layer IL, the resin filling rate of the insulating layer IL may be smaller than the resin filling rate of the magnetic material portion BB. The term "resin filling rate" as used herein refers to the proportion of resin per unit area, and can be measured, for example, as in the example (Demonstration Test 1) described below. With such an insulating layer IL, the resin filling rate of the insulating layer IL is relatively small, so that even if a heat treatment (e.g., reflow) is performed when mounting the coil component on a substrate, reduction of the oxide film covering the metal magnetic particles is unlikely to occur, and deterioration of the insulation resistance is unlikely to occur.

[0041] -Through-hole conductors- Additional components constituting the element body 10 include through-hole conductors. The through-hole conductors (first through-hole conductor TH1 to fourth through-hole conductor TH4) electrically connect the external electrode 20 to one end or the other end of the coil (first coil C1 or second coil C2). The through-hole conductor layer TL may be made of, for example, a metal conductor such as Ag, Cu, and / or Pd. The through-hole conductor layer TL may be formed, for example, by printing a conductive paste on the above-mentioned metal magnetic layer ML.

[0042] -External Electrode- The external electrode 20 is provided on the bottom surface of the element body 10. The external electrode 20 may include a first external electrode 21 to a fourth external electrode 24. The first external electrode 21 to the fourth external electrode 24 are electrically connected to the first through-hole conductor TH1 to the fourth through-hole conductor TH4, respectively. Providing the external electrode 20 on the bottom surface (first main surface 11) of the element body 10 enables the coil component 1 to be properly mounted on a mounting board or the like.

[0043] The first external electrode 21 to the fourth external electrode 24 may each be provided only on the first main surface 11 of the element body 10, or may be provided across the first main surface 11 of the element body 10 and a surface adjacent to the first main surface 11 (one or two of the first end surface 13, the second end surface 14, the first side surface 15, and the second side surface 16).

[0044] The external electrodes 20 may be made of various materials such as Cu and / or Au, for example. The external electrodes 20 may be formed by any method, but may be plated electrodes formed by plating (for example, electroless plating or sputtering), or may have a laminated structure of two or more layers by forming a plated layer of Ni, Sn, or the like on the external electrodes 20 using a plating method after the external electrodes 20 are formed.

[0045] As described above, according to the coil component 1 of the first embodiment, even if resin material is impregnated into the element body after firing the element body to improve the element body strength, it is possible to make it difficult for resin to be impregnated into the element body from outside. As a result, even if a heat treatment (e.g., reflow) is performed when mounting the coil component on a substrate, reduction due to thermal decomposition of the oxide film covering the metal magnetic particles is unlikely to occur, making it possible to make it difficult for deterioration of insulation resistance to occur. Therefore, it is possible to provide a coil component that is difficult to be filled with resin from outside and has improved insulation resistance.

[0046] <Description of Coil Component of Second Embodiment> A coil component of a second embodiment will be described below with reference to Fig. 5 and Fig. 6. In describing the coil component of the second embodiment, explanation of points common to the coil component of the first embodiment will be omitted as appropriate. In other words, the following description will focus on points that are different from the coil component of the first embodiment described above.

[0047] In the coil component 1 of the second embodiment, a resin intrusion prevention portion 30 is provided on the side surface of the insulating layer IL. By providing the resin intrusion prevention portion 30 on the side surface of the insulating layer IL, it is possible to more effectively prevent resin from infiltrating into the insulating layer IL from the outside. Note that FIG. 5 , which illustrates this embodiment, shows an aspect in which the outer surface of the insulating layer IL is provided on an extension line connecting the outer surface of the first coil C1 and the outer surface of the second coil C2 in the stacking direction, but this aspect is not limited to this. For example, as long as the side surface of the insulating layer IL is located inside the side surface of the element body, the insulating layer IL may protrude beyond the outer surfaces of the first coil C1 and the second coil C2. Even in this aspect, providing the resin intrusion prevention portion 30 on the side surface of the insulating layer IL can more effectively prevent resin from infiltrating into the insulating layer IL from the outside.

[0048] In a preferred embodiment of the resin intrusion prevention portion 30, the resin intrusion prevention portion 30 may extend from the side surface of the insulating layer IL to the side surfaces of the first coil C1 and the second coil C2. In other words, the boundary portion BZ between the first coil C1 and the insulating layer IL and the boundary portion BZ between the second coil C2 and the insulating layer IL are covered with the resin intrusion prevention portion 30. This more effectively prevents resin from infiltrating into the insulating layer IL from the outside.

[0049] The resin intrusion prevention portion 30 may be made of ferrite or ceramic. Examples of ferrite include Cu / Zn ferrite, Ni / Zn ferrite, and Mn / Zn ferrite. Examples of ceramic include dielectric ceramic and glass ceramic. By using ferrite or ceramic as the material for the resin intrusion prevention portion 30, it is possible to more effectively prevent resin from infiltrating into the insulating layer IL from the outside.

[0050] Furthermore, the length 30L (see FIG. 5) in the L direction of the resin intrusion prevention portion 30 may be 0.2 to 1 time the length 30T (see FIG. 5) in the T direction of the resin intrusion prevention portion 30. Such a size relationship of the resin intrusion prevention portion 30 can more effectively prevent resin from invading the insulating layer IL from the outside.

[0051] <Description of Coil Component of Third Embodiment> A coil component of a third embodiment will be described below with reference to Figures 7 to 10. In describing the coil component of the third embodiment, explanations of points common to the coil components of the first and second embodiments will be omitted as appropriate. In other words, the following description will focus on points that differ from the coil components of the first and second embodiments described above.

[0052] In the coil component 1 of the third embodiment, the filling rate of the second metal magnetic particles MP2 is higher on the side of the insulating layer IL than on the center of the insulating layer IL. As an example, as shown in FIGS. 7 and 9 , the insulating layer IL has a high filling region A1 on the side of the insulating layer IL and a low filling region A2 on the center of the insulating layer IL. Resin tends to be less likely to penetrate into the high filling region A1, where the filling rate of the second metal magnetic particles MP2 is high. Therefore, by providing the high filling region A1, where the filling rate of the second metal magnetic particles MP2 is high, on the side of the insulating layer IL (i.e., the surface where the insulating layer IL and the magnetic body portion BB contact each other), it is possible to more effectively prevent resin from penetrating into the center of the insulating layer IL from the outside.

[0053] In this specification, the "boundary between the high filling region and the low filling region" refers to the bisector Tc between the tangent line T1 and the tangent line T2 when a tangent line T1 of the second metal magnetic particle MP2 located outermost in the high filling region A1 and a tangent line T2 of the second metal magnetic particle MP2 located outermost in the low filling region A2 are drawn, as shown in Figure 9. The "boundary between the high filling region A1 and the magnetic body portion BB" refers to the bisector Tc between the tangent line T3 and the tangent line T4 when a tangent line T3 of the second metal magnetic particle MP2 located outermost in the high filling region A1 and a tangent line T4 of the first metal magnetic particle MP1 located outermost in the magnetic body portion BB are drawn, as shown in Figure 9.

[0054] As an example, the high filling region A1 may be filled with second metal magnetic particles MP2 having an average particle size of approximately 2 μm at a filling rate of 75 to 80%. Note that the term "filling rate" used in this specification refers to the volume of metal magnetic particles per unit volume. Furthermore, as an example, the low filling region A2 may be filled with metal magnetic particles having an average particle size of approximately 2 μm at a filling rate of 65 to 70%. Such a filling rate relationship can more effectively prevent resin from penetrating from the outside into the center of the insulating layer IL.

[0055] More preferably, the length L1 of the high filling region A1 in the L direction (see FIG. 7) may be 0.1 to 0.5 times the length L2 of the low filling region A2 in the L direction (see FIG. 7). Such a length relationship between the high filling region A1 and the low filling region A2 can more preferably prevent the intrusion of resin from the outside into the center of the insulating layer IL.

[0056] As a modified example of the coil component 1 of the third embodiment, the average particle size of the second metal magnetic particles MP2b on the side of the insulating layer IL may be larger than the average particle size of the second metal magnetic particles MP2a in the center of the insulating layer IL. As an example, as shown in FIG. 10 , the insulating layer IL has a small particle size region A4 in the center of the insulating layer IL and a large particle size region A3 on the side of the insulating layer IL. Resin tends to be less likely to penetrate into the large particle size region A3, where the average particle size of the second metal magnetic particles MP2b is large. Therefore, by providing the large particle size region A3, where the average particle size of the second metal magnetic particles MP2b is large, on the side of the insulating layer IL (i.e., the surface where the insulating layer IL and the magnetic body portion BB contact each other), it is possible to more effectively prevent resin from penetrating into the center of the insulating layer IL from the outside.

[0057] In this specification, the term "boundary between the large particle size region and the small particle size region" refers to the bisector Tc between the tangent line T5 of the second metal magnetic particle MP2b located outermost in the large particle size region A3 and the tangent line T6 of the second metal magnetic particle MP2a located outermost in the small particle size region A4, as shown in Figure 10. The term "boundary between the large particle size region A3 and the magnetic body portion BB" refers to the bisector Tc between the tangent line T7 of the second metal magnetic particle MP2b located outermost in the large particle size region A3 and the tangent line T8 of the first metal magnetic particle MP1 located outermost in the magnetic body portion BB, as shown in Figure 10.

[0058] For example, the large particle size region A3 may be filled with second metal magnetic particles MP2b having an average particle size of approximately 5 μm to 10 μm. Furthermore, the small particle size region A4 may be filled with second metal magnetic particles MP2a having an average particle size of approximately 2 μm to 3 μm. Such a filling rate relationship can more effectively prevent resin from penetrating from the outside into the center of the insulating layer IL. As described above, the average particle size is determined by photographing multiple (e.g., five) areas (e.g., 130 μm x 100 μm) of the cross section of the insulating layer IL using an SEM, and analyzing the resulting SEM images using image analysis software (e.g., WinROOF2021 (manufactured by Mitani Corporation)) to determine the equivalent circle diameter of the metal magnetic particles. The average of the obtained equivalent circle diameters is defined as the average particle size of the metal magnetic particles.

[0059] More preferably, the length L1 of the large grain size regions A3 in the L direction (see FIG. 7) may be 0.1 to 0.5 times the length L2 of the small grain size regions A4 in the L direction (see FIG. 7). Such a length relationship between the large grain size regions A3 and the small grain size regions A4 can more effectively prevent resin from penetrating from the outside into the center of the insulating layer IL.

[0060] <Description of Coil Component of Fourth Embodiment> A coil component of a fourth embodiment will be described below with reference to Fig. 11 and Fig. 12. In describing the coil component of the fourth embodiment, explanation of points common to the coil components of the first to third embodiments will be omitted as appropriate. In other words, the following description will focus on points that are different from the coil components of the first to third embodiments described above.

[0061] In the coil component 1 of the fourth embodiment, voids SP extend from the center of the insulating layer IL toward each of the side surfaces (see FIGS. 11 and 12 ). Because these voids SP are larger than the spacing between the first metal magnetic particles MP1 (or the spacing between the second metal magnetic particles MP2), the voids SP are less likely to be filled with resin by capillary action. Therefore, providing the voids SP in the insulating layer IL more effectively prevents resin from penetrating from the outside into the center of the insulating layer IL.

[0062] The voids SP can be formed by placing a material (e.g., resin beads) in the insulating layer that disappears during the heat treatment process of the element body. The resin beads can be formed in desired positions by screen printing or the like when forming the laminated structure, so the positions where the voids SP are formed can be controlled.

[0063] In a preferred embodiment of the gap SP, the length Ls of the gap SP (see FIG. 11 ) may be 0.7 to 1.0 times the coil width Cs (see FIG. 11 ) in a cross-sectional view. Such a length of the gap SP can more effectively prevent resin from penetrating into the center of the insulating layer IL. Furthermore, the height Ts of the gap (see FIG. 11 ) may be equal to or less than the separation distance between the first coil C1 and the second coil C2, and may be, for example, 2 μm to 4 μm. Note that the terms "coil width Cs," "length Ls of the gap SP," "length Ls of the gap SP," and "separation distance between the first coil C1 and the second coil C2" used in this specification refer to the longest length measured by cross-sectional observation using an SEM image.

[0064] The following demonstration tests were carried out on the coil components of Examples 1 to 3 and a comparative example shown below.

[0065] (Coil component of example 1) The coil component of the first embodiment shown in Fig. 3 was manufactured as the coil component of example 1. Specifically, the coil component was manufactured so that the outer surface of the insulating layer IL was provided on an extension line connecting the outer surface of the first coil C1 and the outer surface of the second coil C2 in the stacking direction.

[0066] (Coil component of example 2) A coil component of the second embodiment shown in Fig. 5 was manufactured as a coil component of example 2. Specifically, a resin intrusion prevention portion 30 was provided on a side surface of the insulating layer IL, and the resin intrusion prevention portion 30 extended from the side surface of the insulating layer IL to the side surfaces of the first coil C1 and the second coil C2.

[0067] Coil component of Example 3 A coil component of the fourth embodiment shown in Fig. 11 was manufactured as a coil component of Example 3. Specifically, a coil component was manufactured in which a gap SP extended from the center of the insulating layer IL toward the side surface.

[0068] (Coil component of the comparative example) As a coil component of the comparative example, a coil component was manufactured in which an insulating layer IL was provided between the first coil C1 and the second coil C2, but the insulating layer IL was exposed from the base body 10, as shown in FIG. 13 .

[0069] <Demonstration Test 1: Measurement of Resin Filling Rate of Insulation Layer> In Demonstration Test 1, the resin filling rates of the coil components of Examples 1 to 3 and the Comparative Example were measured.

[0070] The resin filling rate is measured by the following procedure. (1) A sample cross section is obtained by cutting the element body 10 through the center thereof perpendicular to the mounting surface and end surface of the coil component using a milling machine IM4000 (manufactured by Hitachi High-Tech Corporation). (2) The obtained sample cross section is photographed at a magnification of 1000 to 5000 times using an SEM machine SU-1500 (manufactured by Hitachi High-Tech Corporation). (3) The photographed SEM image is loaded into image analysis software WinROOF (manufactured by Mitani Corporation), and the proportion of resin filling the gaps between the particles is measured.

[0071] The measurement results are shown in Fig. 14. As shown in Fig. 14, the resin filling rates of Examples 1 to 3 were lower than the resin filling rate of the Comparative Example. Therefore, the coil component of the present disclosure can more effectively prevent the intrusion of resin from the outside into the center of the insulating layer IL.

[0072] <Demonstration Test 2: Measurement of Insulation Resistance Between Coils> In Demonstration Test 2, the insulation resistance between coils was measured for the coil components of Examples 1 to 3 and the Comparative Example.

[0073] The insulation resistance is measured using a Digital Electrometer 8252 (manufactured by ADCMT) by placing the measuring terminals on the bottom electrodes of different coils to measure the insulation resistance between the coils.

[0074] According to the results of measuring the insulation resistance, the coil component of the comparative example showed a rise in insulation resistance when heated at 300°C for 1 minute, resulting in deterioration of the insulation resistance. On the other hand, the coil components of Examples 1 to 3 showed a suppressed rise in insulation resistance compared to the coil component of the comparative example, even when heated at 300°C for 1 minute, and had good insulation resistance characteristics.

[0075] The above demonstration tests have shown that the coil component of the present disclosure is less susceptible to resin filling into the body than conventional coil components, making it possible to improve insulation resistance.

[0076] It should be noted that the embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. Therefore, the technical scope of the present disclosure should not be interpreted solely by the above-described embodiments, but should be defined based on the claims. The technical scope of the present disclosure also includes all modifications within the scope and meaning equivalent to the claims.

[0077] The coil component of the present disclosure includes the following aspects: <1> A coil component comprising: an element body having a magnetic material part containing first metal magnetic particles and a resin, and a coil embedded in the magnetic material part; and an external electrode provided on a mounting surface of the element body and connected to the coil, wherein the coil includes a first coil and a second coil, the first coil and the second coil are each formed of a coil conductor and arranged opposite each other, an insulating layer including second metal magnetic particles is arranged on at least a portion along the opposing surface between the first coil and the second coil, the average particle size of the second metal magnetic particles is smaller than the average particle size of the first metal magnetic particles, and a side surface of the insulating layer is located inside a side surface of the element body in a plan view. <2> The coil component according to <1>, wherein the resin filling rate of the insulating layer is smaller than that of the magnetic material part. <3> The coil component according to <1> or <2>, wherein a resin intrusion prevention portion is provided on a side surface of the insulating layer. <4> The coil component according to <3>, wherein the resin intrusion prevention portion extends from a side surface of the insulating layer to a side surface of the first coil and a side surface of the second coil. <5> The coil component according to <3> or <4>, wherein the resin intrusion prevention portion is made of ferrite or ceramic. <6> The coil component according to any one of <1> to <5>, wherein the insulating layer has a higher filling rate of the second metal magnetic particles on the side surface of the insulating layer than on the center of the insulating layer. <7> The coil component according to any one of <1> to <6>, wherein the insulating layer has a larger average particle size of the second metal magnetic particles on the side surface of the insulating layer than on the center of the insulating layer. <8> The coil component according to any one of <1> to <7>, wherein the insulating layer has voids extending from the center to each of the lateral surfaces of the insulating layer. <9> The coil component according to <8>, wherein the length of the voids is 0.7 to 1.0 times the coil width in a cross-sectional view. <10> The coil component according to any one of <1> to <9>, wherein, in a plan view, the insulating layer does not protrude from the first coil and the second coil.

[0078] The coil component of the present disclosure is difficult to be filled with resin and can be used as an electronic component that improves insulation resistance.

[0079] 1 Coil component 10 Body 11 First main surface 12 Second main surface 13 First end surface 14 Second end surface 15 First side surface 16 Second side surface 20 External electrode 21 First external electrode 22 Second external electrode 23 Third external electrode 24 Fourth external electrode 30 Resin intrusion prevention portion MP1 First metal magnetic particle MP2, MP2a, MP2b Second metal magnetic particle IC1, IC2, IC2a, IC2b Insulating coating BB Magnetic portion C1 First coil C2 Second coil IL Insulating layer A1 High filling region A2 Low filling region A3 Large particle size region A4 Small particle size region SP Air gap T1 to T8 Tangent Tc Bisector

Claims

1. A coil component comprising: a base body having a magnetic part containing first metal magnetic particles and resin, and a coil embedded in the magnetic part; an external electrode provided on the mounting surface of the base body and connected to the coil, wherein the coil comprises a first coil and a second coil, the first coil and the second coil are each formed from a coil conductor and arranged opposite each other, an insulating layer having second metal magnetic particles is arranged along at least a portion of the opposing surface between the first coil and the second coil, the average particle size of the second metal magnetic particles is smaller than the average particle size of the first metal magnetic particles, and the side of the insulating layer is located inside the side of the base body in a plan view.

2. The coil component according to claim 1, wherein the resin filling rate of the insulating layer is lower than the resin filling rate of the magnetic material portion.

3. A coil component according to claim 1 or 2, wherein a resin intrusion prevention portion is provided on the side surface of the insulating layer.

4. The coil component according to claim 3, wherein the resin intrusion prevention portion extends from a side surface of the insulating layer to side surfaces of the first coil and the second coil.

5. A coil component according to claim 3 or 4, wherein the resin intrusion prevention portion is made of ferrite or ceramic.

6. A coil component described in any one of claims 1 to 5, wherein the insulating layer has a higher filling rate of the second metal magnetic particles on the side of the insulating layer than in the center of the insulating layer.

7. A coil component according to any one of claims 1 to 6, wherein the average particle size of the second metal magnetic particles on the side of the insulating layer is larger than the average particle size of the second metal magnetic particles in the center of the insulating layer.

8. A coil component according to any one of claims 1 to 7, wherein the insulating layer has gaps extending from the center to each of the side surfaces of the insulating layer.

9. The coil component according to claim 8, wherein the length of the gap is 0.7 to 1.0 times the coil width in cross section.

10. A coil component according to any one of claims 1 to 9, wherein, in a plan view, the insulating layer does not protrude from the first coil and the second coil.

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