Multilayer coil parts

Abstract

To provide a laminated coil component capable of suppressing breakage of a coil due to a crack.SOLUTION: In a laminated coil component 1, between multiple metal magnetic particles M, M in an element body 2, there are filled parts V1 with resin R and void parts V2 that are not filled with the resin R. One of a main surfaces 2b of the element body 2 serves as a mounting surface P for an external electronic component, and an edge 4e of an external electrode 4 is located on the mounting surface P. In the element body 2, a high-void area F in which the void ratio of the void part V2 is higher than the void ratio of other parts in the element body 2 extends from the edge 4e of the external electrode 4 on the mounting surface P toward an end surface 2a of the element body 2.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] An example of a conventional laminated coil component is the coil component described in Patent Document 1. The body of this conventional coil component contains a plurality of metal particles made of a soft magnetic alloy. At least a portion of the voids generated by the accumulation of the metal particles is filled with a resin material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-238841 A Summary of the Invention [Problem to be solved by the invention]

[0004] A multilayer coil component is mounted on a substrate, for example, by soldering external electrodes provided at the ends of the element body to lands on the substrate. After mounting, stress may occur in the multilayer coil component due to bending of the substrate. If excessive stress is applied to the multilayer coil component, cracks may occur in the element body. If a crack progresses inside the element body and reaches the coil inside the element body, the coil may break.

[0005] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide a laminated coil component that can suppress breakage of the coil due to cracks. [Means for solving the problem]

[0006] A laminated coil component according to one aspect of the present disclosure comprises a base body containing a plurality of metal magnetic particles, a coil arranged within the base body, and an external electrode arranged to cover an end face of the base body and electrically connected to the coil, wherein in the base body, between the plurality of metal magnetic particles, there are portions filled with resin and void portions not filled with resin, one side of the base body except for the end face serves as a mounting surface for an external electronic component, and the edges of the external electrodes are located on the mounting surface, and within the base body, a high-gap region in which the void rate due to the void portion is higher than the void rate of other parts of the base body extends from the edges of the external electrodes on the mounting surface towards the end face of the base body.

[0007] In this laminated coil component, the high void region extends from the edge of the external electrode on the mounting surface toward the end face of the element body. The edge of the external electrode on the mounting surface is a location that can become the starting point of a crack when excessive stress is generated in the element body. In the high void region, the porosity is higher than the porosity of other parts of the element body, so the strength of the element body is relatively low. Therefore, if a crack occurs in the element body, the propagation direction of the crack is guided by the high void region from the starting point toward the end face of the element body. By guiding the propagation direction of the crack toward the end face of the element body, it is possible to reduce the possibility of the crack reaching the coil inside the element body, and coil breakage due to the crack can be suppressed.

[0008] The external electrodes may be baked electrodes, in which case the propagation direction of the crack can be more reliably guided toward the end face of the element body, further reducing the possibility that the crack will reach the coil inside the element body.

[0009] The high void region may extend to the end face of the element body, which can more reliably guide the propagation direction of a crack toward the end face of the element body, thereby further reducing the possibility that the crack will reach the coil inside the element body.

[0010] The high void region may be spaced apart from the coil, which further reduces the likelihood of a crack reaching the coil within the element. Effect of the Invention

[0011] According to the present disclosure, breakage of the coil due to cracks can be suppressed. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view showing an embodiment of a laminated coil component. [Diagram 2] 2 is a diagram showing a cross-sectional configuration of the laminated coil component shown in FIG. 1. [Diagram 3] FIG. 2 is a perspective view showing a configuration of a coil. [Figure 4] FIG. 2 is an enlarged schematic diagram showing a cross-sectional configuration inside the element body. [Diagram 5] FIG. 2 is a schematic cross-sectional view showing an arrangement of high void regions in an element body. [Figure 6] FIG. 2 is an enlarged schematic diagram showing a cross-sectional configuration of a high void region. [Figure 7] FIG. 11 is a schematic cross-sectional view showing the progression of a crack in a laminated coil component of a comparative example in which a high-void region is not provided. [Figure 8] FIG. 11 is a schematic cross-sectional view showing the progression of a crack in a laminated coil component according to an embodiment in which a high void region is provided. [Figure 9] 13 is a diagram showing a cross-sectional configuration of a laminated coil component according to a modified example. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, preferred embodiments of a laminated coil component according to one aspect of the present disclosure will be described in detail with reference to the drawings.

[0014] The configuration of a laminated coil component 1 according to the present embodiment will be described with reference to Fig. 1 to Fig. 3. Fig. 1 is a perspective view showing one embodiment of a laminated coil component. Fig. 2 is a view showing a cross-sectional configuration of the laminated coil component shown in Fig. 1. Fig. 3 is a perspective view showing the configuration of a coil.

[0015] As shown in Fig. 1, the laminated coil component 1 includes a rectangular parallelepiped element body 2 and a pair of external electrodes 4, 4. The pair of external electrodes 4, 4 are disposed at both ends of the element body 2, respectively, and are spaced apart from each other. The rectangular parallelepiped shape includes a rectangular parallelepiped shape with chamfered corners and ridges, and a rectangular parallelepiped shape with rounded corners and ridges. The laminated coil component 1 can be used, for example, as a bead inductor or a power inductor.

[0016] The rectangular parallelepiped element body 2 has a pair of end faces 2a, 2a facing each other, a pair of main faces 2b, 2b facing each other, and a pair of side faces 2c, 2c facing each other. The end faces 2a, 2a are positioned so as to be adjacent to the pair of main faces 2b, 2b. The end faces 2a, 2a are also positioned so as to be adjacent to the pair of side faces 2c, 2c. One of the main faces 2b (the bottom face in FIG. 1) serves as a mounting surface P. The mounting surface P is the surface that faces another electronic device (such as a circuit board or electronic component) when the laminated coil component 1 is mounted on the other electronic device.

[0017] In this embodiment, the opposing direction (first direction D1) of the pair of end faces 2a, 2a is defined as the length direction of the element body 2. The opposing direction (second direction D2) of the pair of main faces 2b, 2b is defined as the height direction of the element body 2. The opposing direction (third direction D3) of the pair of side faces 2c, 2c is defined as the width direction of the element body 2. The first direction D1, the second direction D2, and the third direction D3 are perpendicular to each other.

[0018] The length of the element body 2 in the first direction D1 is greater than the lengths of the element body 2 in the second direction D2 and the third direction D3. The length of the element body 2 in the second direction D2 is equal to the length of the element body 2 in the third direction D3. That is, in this embodiment, the pair of end faces 2a, 2a are square-shaped, and the pair of main faces 2b, 2b and the pair of side faces 2c, 2c are rectangular-shaped.

[0019] The length of the element body 2 in the first direction D1 may be equal to the length of the element body 2 in the second direction D2 and the third direction D3. The length of the element body 2 in the second direction D2 may be different from the length of the element body 2 in the third direction D3. "Equal" includes not only equality but also slight differences or manufacturing errors within a preset range. For example, if multiple values ​​are within a range of ±5% of the average value of the multiple values, these values ​​may be considered to be equal.

[0020] The pair of end faces 2a, 2a extend in the second direction D2 to connect the pair of main faces 2b, 2b. The pair of end faces 2a, 2a also extend in the third direction D3 to connect the pair of side faces 2c, 2c. The pair of main faces 2b, 2b extend in the first direction D1 to connect the pair of end faces 2a, 2a. The pair of main faces 2b, 2b also extend in the third direction D3 to connect the pair of side faces 2c, 2c. The pair of side faces 2c, 2c extend in the first direction D1 to connect the pair of end faces 2a, 2a. The pair of side faces 2c, 2c also extend in the second direction D2 to connect the pair of main faces 2b, 2b.

[0021] The element body 2 is constructed by stacking a plurality of magnetic layers 11 (see FIG. 3). The magnetic layers 11 are stacked in the opposing direction of the main surfaces 2b, 2b. That is, the stacking direction of the magnetic layers 11 coincides with the opposing direction of the main surfaces 2b, 2b (hereinafter, the opposing direction of the main surfaces 2b, 2b will be referred to as the "stacking direction"). Each magnetic layer 11 has a substantially rectangular shape. In the actual element body 2, the magnetic layers 11 are integrated to the extent that the boundaries between the layers are not visible.

[0022] As shown in Figures 2 and 3, a coil 15 is disposed within the element body 2. The coil 15 includes a plurality of coil conductors 16a-16f. The plurality of coil conductors 16a-16f include a conductive material (e.g., Ag or Pd). The plurality of coil conductors 16a-16f are configured as a sintered body of a conductive paste including a conductive material (e.g., Ag powder or Pd powder).

[0023] The coil conductor 16a includes a connecting conductor 17. The connecting conductor 17 is arranged on one end face 2a side of the element body 2, and has an end exposed at one end face 2a. The end of the connecting conductor 17 is exposed at one end face 2a at a position closer to one main face 2b, and is connected to one external electrode 4. In other words, the coil 15 is electrically connected to one external electrode 4 via the connecting conductor 17. In this embodiment, the conductor pattern of the coil conductor 16a and the conductor pattern of the connecting conductor 17 are formed integrally and continuously.

[0024] The coil conductor 16f includes a connecting conductor 18. The connecting conductor 18 is arranged on the other end face 2a side of the element body 2, and has an end exposed at the other end face 2a. The end of the connecting conductor 18 is exposed at a position on the other end face 2a closer to the other main face 2b, and is connected to the other external electrode 4. In other words, the coil 15 is electrically connected to the other external electrode 4 via the connecting conductor 18. In this embodiment, the conductor pattern of the coil conductor 16f and the conductor pattern of the connecting conductor 18 are formed integrally and continuously.

[0025] The multiple coil conductors 16a to 16f are formed in the stacking direction of the magnetic layers 11 in the element body 2. The multiple coil conductors 16a to 16f are arranged in the following order: coil conductor 16a, coil conductor 16b, coil conductor 16c, coil conductor 16d, coil conductor 16e, and coil conductor 16f. In this embodiment, the coil 15 is composed of the portion of the coil conductor 16a other than the connecting conductor 17, the multiple coil conductors 16b to 16d, and the portion of the coil conductor 16f other than the connecting conductor 18.

[0026] The ends of the coil conductors 16a to 16f are connected to each other by through-hole conductors 19a to 19e. The coil conductors 16a to 16f are electrically connected to each other by the through-hole conductors 19a to 19e. The coil 15 is formed by electrically connecting the coil conductors 16a to 16f. Each of the through-hole conductors 19a to 19e contains a conductive material (e.g., Ag or Pd). Each of the through-hole conductors 19a to 19e, like the coil conductors 16a to 16f, is formed as a sintered body of a conductive paste containing a conductive material (e.g., Ag powder or Pd powder).

[0027] The external electrode 4 is disposed so as to cover the end portion on the end face 2a side of the element body 2. As shown in Fig. 1, the external electrode 4 has an electrode portion 4a covering the end face 2a, electrode portions 4b, 4b extending over the pair of principal faces 2b, 2b, and electrode portions 4c, 4c extending over the pair of side faces 2c, 2c. In other words, the external electrode 4 is formed by five faces, the electrode portions 4a, 4b, 4c.

[0028] The electrode portion 4a is disposed so as to cover the entire ends of the connecting conductors 17, 18 exposed at the end face 2a, and the connecting conductors 17, 18 are directly connected to the external electrode 4. That is, the connecting conductors 17, 18 connect the ends of the coil 15 to the electrode portion 4a. As a result, the coil 15 is electrically connected to the external electrode 4.

[0029] Adjacent electrode parts 4a, 4b, 4c are continuous and electrically connected to each other at the ridges of element body 2. Electrode parts 4a and 4b are connected to each other at the ridges between end face 2a and main face 2b. Electrode parts 4a and 4c are connected to each other at the ridges between end face 2a and side face 2c.

[0030] The external electrode 4 is configured to include a conductive material. The conductive material is, for example, Ag or Pd. The external electrode 4 is a fired electrode, and is configured as a sintered body of a conductive paste. The conductive paste includes a conductive metal powder and a glass frit. The conductive metal powder is, for example, Ag powder or Pd powder. A plating layer is formed on the surface of the external electrode 4. The plating layer is formed by, for example, electroplating. The electroplating is, for example, Ni electroplating or Sn electroplating.

[0031] Next, the configuration of the above-mentioned element body 2 will be described in more detail.

[0032] FIG. 4 is a schematic diagram showing an enlarged cross-sectional configuration inside the element body. As shown in the figure, the element body 2 contains a plurality of metal magnetic particles M. The metal magnetic particles M are, for example, made of a soft magnetic alloy. The soft magnetic alloy is, for example, an Fe-Si based alloy. When the soft magnetic alloy is an Fe-Si based alloy, the soft magnetic alloy may contain P. The soft magnetic alloy may be, for example, an Fe-Ni-Si-M based alloy. "M" contains one or more elements selected from Co, Cr, Mn, P, Ti, Zr, Hf, Nb, Ta, Mo, Mg, Ca, Sr, Ba, Zn, B, Al, and rare earth elements.

[0033] In the element body 2, the metal magnetic particles M, M are bonded to each other. The bond between the metal magnetic particles M, M is realized, for example, by bonding between oxide films formed on the surfaces of the metal magnetic particles M. The average particle diameter of the metal magnetic particles M is, for example, 0.5 μm to 15 μm. In this embodiment, the average particle diameter of the metal magnetic particles M is 5 μm. The "average particle diameter" refers to the particle diameter at an integrated value of 50% in a particle size distribution determined by a laser diffraction / scattering method.

[0034] As shown in FIG. 4, the element body 2 contains resin R. The resin R exists between the multiple metal magnetic particles M, M. The resin R is an electrically insulating resin. Examples of the resin R that can be used include silicone resin, phenol resin, acrylic resin, and epoxy resin. The resin R does not completely fill the spaces between the multiple metal magnetic particles M, M in the element body 2. Therefore, in the element body 2, between the multiple metal magnetic particles M, M, there are filled portions V1 with resin R and void portions V2 that are not filled with resin R.

[0035] Within the element body 2, a high gap region F is provided in which the void ratio of the void portion V2 is higher than the void ratio of other parts within the element body 2. As shown in FIG. 5, the high gap region F extends from the edge 4e of the external electrode 4 on the mounting surface P toward the end surface 2a of the element body 2. The edge 4e of the external electrode 4 is a tip of the electrode portion 4b that protrudes onto the mounting surface P, which is one of the pair of main surfaces 2b, 2b. The high gap region F includes a portion on the mounting surface P that is in contact with the edge 4e of the external electrode 4, and extends from that portion in the first direction D1 to reach the end surface 2a of the element body 2. In this embodiment, the high gap region F extends to include a portion on the mounting surface P that is in contact with the external electrode 4. Therefore, the high gap region F extends to reach the corner formed by the end surface 2a and the mounting surface P. In FIG. 5, one of the external electrodes 4 is shown enlarged, but the other external electrode 4 has a similar configuration.

[0036] The depth of the high gap region F from the mounting surface P is smaller than the distance in the second direction D2 from the mounting surface P to the coil conductor 16f that is closest to the mounting surface P. This causes the high gap region F to be separated from the coil 15 in the element body 2. The depth of the high gap region F from the mounting surface P may be constant in the first direction D1, or may gradually decrease from the edge 4e of the external electrode 4 toward the end face 2a. The depth of the high gap region F from the mounting surface P may gradually increase from the edge 4e of the external electrode 4 toward the end face 2a.

[0037] As shown in FIG. 6, the high void region F is similar to the other parts of the element body 2 in that resin R is present between the multiple metal magnetic particles M, M. Also, like the other parts of the element body 2, void portions V2 are present at least partially between the multiple metal magnetic particles M, M. Meanwhile, whereas the porosity of the other parts of the element body 2 is, for example, less than 10%, the porosity of the high void region F is around 30%. The porosity can be calculated, for example, by magnifying the cross section of the element body 2 3000 times with a scanning electron microscope (SEM) and determining the ratio of the area of ​​the void portions V2 to the area of ​​the cross section of the element body 2.

[0038] When a crack occurs in the element body 2, the high void region F acts to guide the direction of crack progression. FIG. 7 is a schematic cross-sectional view showing the progression of a crack in a laminated coil component of a comparative example in which a high void region is not provided. As shown in the figure, the laminated coil component 101 of the comparative example differs from the laminated coil component 1 of the example in that a high void region F is not provided in the element body 102. In the laminated coil component 101, the void ratio is less than 10% throughout the element body 102. The laminated coil component 1 is mounted on the substrate 51 by joining lands 52 on the substrate 51 side to external electrodes 104 with solder 53.

[0039] After mounting, stress may occur in the laminated coil component 101 due to bending of the substrate 51, etc. When excessive stress is applied to the laminated coil component 101, a crack K may occur in the element body 102. In this case, an edge 104e of the external electrode 104 on the mounting surface P may become the starting point of the crack K when excessive stress occurs in the element body 102. In a laminated coil component 101 in which the element body 102 is not provided with a high void region F, it is difficult to predict the progression direction of the crack K in the element body 102. As shown in FIG. 7, when the crack K progresses from the starting point in the second direction D2, it is considered that the crack K will reach the coil 15 in the element body 102, causing a break in the coil 115.

[0040] In contrast, in a laminated coil component 1 in which the element body 2 is provided with a high void region F, the strength of the element body 2 is relatively lower in the high void region F than in other parts of the element body 2. For this reason, in the laminated coil component 1, when a crack K occurs in the element body 2, the propagation direction of the crack K is guided by the high void region F from its starting point toward the end face 2a of the element body 2, as shown in Fig. 8. By guiding the propagation direction of the crack K toward the end face 2a of the element body 2 on which the external electrode 4 is provided, it is possible to reduce the possibility of the crack K reaching the coil 15 in the element body 2, and breakage of the coil due to the crack K can be suppressed.

[0041] In this embodiment, the external electrode 4 is a fired electrode. This makes it possible to more reliably guide the progression of the crack K toward the end surface 2a of the element body 2 on which the external electrode 4 is provided. In this embodiment, the high gap region F extends to the end surface 2a of the element body 2. This makes it possible to more reliably guide the progression of the crack K to the end surface 2a of the element body 2. This further reduces the possibility that the crack K will reach the coil 15 in the element body 2. In this embodiment, the high gap region F is separated from the coil 15. This makes it possible to prevent the progression of the crack K from being directed toward the coil 15, and further reduces the possibility that the crack K will reach the coil 15 in the element body.

[0042] The present disclosure is not limited to the above embodiment. For example, the high-gap region F may have a portion extending in the first direction D1 from the edge 4e of the external electrode 4 toward the center of the element body 2 (the side opposite to the end face 2a) (see FIG. 5). The depth of the high-gap region F from the mounting surface P in this portion may be equal to the depth of the high-gap region F extending from the edge of the external electrode 4 toward the end face 2a of the element body 2, or may gradually decrease with increasing distance from the edge 4e of the external electrode 4.

[0043] The high void region F only needs to have a portion extending from the edge 4e of the external electrode 4 toward the end face 2a of the element body 2, and does not necessarily have to extend all the way to the end face 2a. The external electrode 4 is not limited to a baked electrode, and may be a resin electrode. The resin electrode is an electrode formed by mixing a thermosetting resin with a conductive powder and an organic solvent. Examples of the thermosetting resin that can be used include silicone resin, phenol resin, acrylic resin, epoxy resin, and polyimide resin. Examples of the conductive powder that can be used include Ag powder.

[0044] In the magnetic layer 11, non-magnetic ceramic particles having a smaller diameter than the metal magnetic particles M may be present at least partially between the plurality of metal magnetic particles M, M.

[0045] In the above embodiment, the main surface 2b of the element body 2 is the mounting surface P, and the lamination direction of the magnetic layer 11 coincides with the normal direction of the mounting surface P. However, for example, as shown in FIG. 9, the lamination direction of the magnetic layer and the normal direction of the mounting surface may intersect (orthogonal). In a laminated coil component 61 shown in FIG. 9, external electrodes 64 are provided so as to cover the end faces 62a, 62a of the element body 62, and the lamination direction of the magnetic layer coincides with the direction connecting the end faces 62a, 62a of the element body 62. That is, in the laminated coil component 61, the formation direction of the coil 75 in the element body 62 coincides with the direction connecting the end faces 62a, 62a of the element body 62 and is orthogonal to the normal direction of the mounting surface P. In such a laminated coil component 61, by providing a high gap region F extending from an edge 64e of the external electrode 64 on the mounting surface P toward the end face 62a of the element body 62, the same effects as those of the above embodiment can be achieved. [Explanation of symbols]

[0046] 1...laminated coil component, 2...element body, 2a...end surface, 4...external electrode, 4e...edge, 15...coil, F...high gap region, M...metal magnetic particle, P...mounting surface, V1...filled portion, V2...gap portion, K...crack.

Claims

1. An element body including a plurality of metal magnetic particles; A coil disposed within the element body; an external electrode disposed so as to cover an end surface of the element body and electrically connected to the coil; In the element body, between the plurality of metal magnetic particles, there are portions filled with resin and void portions not filled with resin, a surface of the element body other than the end surface serves as a mounting surface for an external electronic component, and edges of the external electrodes are located on the mounting surface; a high-gap region in which the void ratio is higher than the void ratio of other portions of the element body extends from an edge of the external electrode on the mounting surface toward an end face of the element body, a depth of the high-gap region from the mounting surface gradually decreases from the edge of the external electrode toward the end surface.

2. An element body including a plurality of metal magnetic particles; A coil disposed within the element body; an external electrode disposed so as to cover an end surface of the element body and electrically connected to the coil; In the element body, between the plurality of metal magnetic particles, there are portions filled with resin and void portions not filled with resin, a surface of the element body other than the end surface serves as a mounting surface for an external electronic component, and edges of the external electrodes are located on the mounting surface; a high-gap region in which the void ratio is higher than the void ratio of other portions of the element body extends from an edge of the external electrode on the mounting surface toward an end face of the element body, a depth of the high-gap region from the mounting surface is greater on the end face side relative to a portion where an edge of the external electrode is located, and is smaller on the side opposite the end face.

3. 3. The laminated coil component according to claim 1, wherein the external electrodes are baked electrodes.

4. 4. The laminated coil component according to claim 1, wherein the high gap region extends to the end face of the element body.

5. 5. The laminated coil component according to claim 1, wherein the high gap region is spaced apart from the coil.

6. 6. The laminated coil component according to claim 1, wherein the high-gap region has a portion extending toward an end face of the element body opposite the end face.

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