Multilayer inductor
The multilayer inductor design with internal and auxiliary conductors addresses overheating and melting issues by redistributing current, enhancing reliability and stability.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2021-03-23
- Publication Date
- 2026-03-03
AI Technical Summary
Conventional inductors with through conductors are prone to overheating and melting at the joint surfaces when a defect occurs, leading to unreliable operation due to overcurrent flow through remaining conductors.
A multilayer inductor design featuring internal electrodes with through and auxiliary conductors, where auxiliary conductors are joined to external electrodes, redistributing current flow to prevent overheating and melting.
The design enhances reliability by suppressing overheating and melting at joint surfaces, ensuring stable operation even with conductor defects.
Smart Images
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Abstract
Description
[Technical Field]
[0001] The present invention relates to a multilayer inductor. [Background technology]
[0002] Conventionally, inductors having through conductors that extend linearly within an element body have been known. Patent Document 1 listed below discloses an inductor that has an element body having a pair of end faces facing each other, three through conductors extending between the end faces, and a pair of external electrodes provided on both end faces of the element body and connected to each through conductor. [Prior art documents] [Patent documents]
[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 59-72708 Summary of the Invention [Problem to be solved by the invention]
[0004] When the through conductor is doubled (i.e., current flows through each of multiple through conductors connected in parallel) as in the inductor according to the prior art described above, a current within a specified current value range flows through each of the multiple through conductors. If a defect such as a break occurs in one of the through conductors, a current exceeding the specified current value range (overcurrent) flows through the remaining through conductors. In this case, the joint surface between the through conductor and the external electrode, which is an area with relatively high electrical resistance, overheats, and melting can occur starting from the joint surface.
[0005] An object of one aspect of the present invention is to provide a multilayer inductor with improved reliability. [Means for solving the problem]
[0006] A laminated inductor according to one aspect of the present invention comprises a base body including a plurality of stacked magnetic layers and having a pair of end faces facing each other, an internal electrode provided within the base body and extending between the pair of end faces, and a pair of external electrodes provided on each end face of the base body and joined to the internal electrode exposed at the end faces, the internal electrode extending between the end faces in the opposing direction of the pair of end faces and having a plurality of through conductors whose ends are exposed at the end faces, and auxiliary conductors extending between the ends of the plurality of through conductors and exposed at the end faces.
[0007] The above-mentioned laminated inductor is provided with auxiliary conductors that are joined to the external electrodes at the end faces of the element body. Therefore, even if a malfunction occurs in some of the through conductors, overheating at the joint surfaces between the internal and external electrodes is suppressed, and melting starting from the joint surfaces is suppressed, thereby achieving high reliability.
[0008] In a multilayer inductor according to another aspect, the internal electrodes are located between a single layer of a plurality of magnetic layers.
[0009] In a multilayer inductor according to another aspect, the internal electrodes are located between a plurality of magnetic layers.
[0010] In a multilayer inductor according to another aspect, the plurality of through conductors include a pair of through conductors arranged in the stacking direction of the element body.
[0011] A laminated inductor according to another aspect includes a plurality of through conductors, including a first through conductor and a second through conductor located between the same layers of a plurality of magnetic layers, and a third through conductor and a fourth through conductor located between the same layers different from the layers between which the first through conductor and the second through conductor are located, and which are aligned with the first through conductor and the second through conductor, respectively, along the stacking direction of the element body.
[0012] In a multilayer inductor according to another aspect, the length of the auxiliary conductor in a first direction perpendicular to the stacking direction of the element body and the opposing direction of the pair of end faces is 20 to 50% of the length of the element body in the first direction.
[0013] In a multilayer inductor according to another aspect, the length of the auxiliary conductor in a second direction parallel to the opposing direction of the pair of end faces is 2 to 20% of the length of the element body in the second direction. [Effects of the Invention]
[0014] According to various aspects of the present invention, a multilayer inductor with improved reliability is provided. [Brief explanation of the drawings]
[0015] [Figure 1] FIG. 1 is a perspective view showing a multilayer inductor according to an embodiment. [Figure 2] 2 is a perspective view showing an internal electrode of the element body shown in FIG. 1. FIG. [Figure 3] FIG. 3 is a plan view showing the internal electrode shown in FIG. [Figure 4] 4 is a cross-sectional view of the element body shown in FIG. 2 taken along line IV-IV. [Figure 5] 3 is a cross-sectional view of the element body shown in FIG. 2 taken along line VV. [Figure 6] FIG. 3 is a cross-sectional view showing a state in which an internal electrode and an external electrode are joined together. [Figure 7] 5 is a plan view showing an internal electrode having a different configuration from that shown in FIG. 4. [Figure 8] 3 is a perspective view showing an internal electrode of an element body having a different configuration from that shown in FIG. 2. [Figure 9] 9 is a cross-sectional view of the element body shown in FIG. 8 taken along line IX-IX. [Figure 10] 9 is a perspective view showing an internal electrode of an element body having a different configuration from that of FIG. 8. FIG. DETAILED DESCRIPTION OF THE INVENTION
[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements are designated by the same reference numerals, and redundant explanations will be omitted.
[0017] The configuration of the multilayer inductor according to the embodiment will be described with reference to Figures 1 to 4. As shown in Figure 1, the multilayer inductor 10 according to the embodiment is configured to include an element body 12 and a pair of external electrodes 14A, 14B.
[0018] The element body 12 has a substantially rectangular parallelepiped shape and a pair of end faces 12a, 12b that face each other in the extension direction of the element body 12. The element body 12 further has four side faces 12c to 12f that extend in the direction in which the end faces 12a, 12b face each other and connect the end faces 12a, 12b. The side face 12d is the mounting face that faces the mounting substrate when the multilayer inductor 10 is mounted, and the side face 12c facing the side face 12d becomes the top face when mounted. The dimensions of the element body 12 are, for example, length (L) as the dimension in the direction in which the end faces 12a, 12b face each other, width (W) as the dimension in the direction in which the side faces 12e, 12f face each other, and thickness as the dimension in the direction in which the side faces 12c, 12d face each other, and are 2.5 mm long, 2 mm wide, and 0.9 mm thick.
[0019] The element body 12 has a configuration in which an internal electrode 20 is provided inside a magnetic body 18. As shown in Fig. 4, the element body 12 has a layered structure in which multiple magnetic layers 19 that make up the magnetic body 18 are stacked in the opposing direction of side surfaces 12c, 12d. In the following description, the opposing direction of side surfaces 12c, 12d is also referred to as the stacking direction of the element body 12.
[0020] The magnetic body 18 is made of a magnetic material such as ferrite. The magnetic body 18 is obtained by stacking and firing a plurality of magnetic pastes (e.g., ferrite paste) that become the magnetic layers 19. In other words, the element body 12 has a printed laminated structure in which magnetic layers 19, on which magnetic pastes are printed, are stacked, and is a fired element body in which the fired magnetic layers 19 are stacked. The number of magnetic layers 19 that make up the element body 12 is, for example, 150. In the actual element body 12, the plurality of magnetic layers 19 are integrated to the extent that the boundaries between the layers are not visible.
[0021] As shown in Figures 2 and 3, the internal electrode 20 extends between a pair of end faces 12a, 12b. As shown in Figure 4, the entire internal electrode 20 is located between a single layer of multiple magnetic layers 19. The internal electrode 20 is made of a conductive material containing a metal such as Ag. The internal electrode 20 is formed by a printing method. Specifically, it is obtained by applying a conductive paste (for example, Ag paste) that will become the internal electrode 20 onto a magnetic paste that will become the magnetic layers 19 and firing it.
[0022] The internal electrode 20 includes a pair of through conductors 22, 24 extending in the opposing direction of the end faces 12a, 12b. Both of the through conductors 22, 24 extend between the end faces 12a, 12b (i.e., from the end face 12a to the end face 12b of the element body 12). The through conductor 22 has an end 22a on the end face 12a side and an end 22b on the end face 12b side. Similarly, the through conductor 24 has an end 24a on the end face 12a side and an end 24b on the end face 12b side. The through conductor 22 is exposed at the end face 12a at the end 22a and at the end face 12b at the end 22b. Similarly, the through conductor 24 is exposed at the end face 12a at the end 24a and at the end face 12b at the end 24b.
[0023] In this embodiment, each of the through conductors 22, 24 has a strip shape with a uniform width and height. As shown in FIG. 5, each of the through conductors 22, 24 according to this embodiment has a cross-sectional shape perpendicular to the opposing direction of the end faces 12a, 12b, in which the two corners of a rectangle extending parallel to the mounting surface (side surface 12c) are rounded (a so-called semi-cylindrical cross-section). The cross-sectional shape of each of the through conductors 22, 24 may be a rectangle extending parallel to the mounting surface, or may be a semi-ellipse with the mounting surface side flat. In this embodiment, each of the through conductors 22, 24 has a uniform width and height along its entire length. In this embodiment, the through conductors 22, 24 have the same dimensions, e.g., 2.5 mm long, 0.4 mm wide, and 0.1 mm thick.
[0024] The internal electrode 20 further includes a pair of auxiliary conductors 26, 28. The auxiliary conductor 26 extends between the end 22a of the through conductor 22 and the end 24a of the through conductor 24. The auxiliary conductor 28 extends between the end 22b of the through conductor 22 and the end 24b of the through conductor 24. Each auxiliary conductor 26, 28 is integral with the pair of through conductors 22, 24. Each auxiliary conductor 26, 28 extends along the end faces 12a, 12b and is exposed at the end faces 12a, 12b over its entire length in the width direction of the element body 12 (the direction in which the side faces 12e, 12f face each other). In this embodiment, each auxiliary conductor 26, 28 is strip-shaped and extends in the width direction of the element body 12, with a uniform width and height. In this embodiment, the auxiliary conductors 26, 28 have the same dimensions, e.g., 0.1 mm long, 0.4 mm wide, and 0.1 mm thick. The length of the auxiliary conductors 26, 28 may be in the range of 0.1 to 1.0 mm.
[0025] A pair of external electrodes 14A, 14B are provided on end faces 12a, 12b, respectively, of the element body 12. The external electrode 14A covers the entire area of the end face 12a and is in direct contact with and bonded to the through conductors 22, 24 and auxiliary conductor 26 of the internal electrode 20 exposed at the end face 12a. Similarly, the external electrode 14B covers the entire area of the end face 12b and is in direct contact with and bonded to the through conductors 22, 24 and auxiliary conductor 28 of the internal electrode 20 exposed at the end face 12b. In this embodiment, as shown in Fig. 1, each external electrode 14A, 14B integrally covers the end faces 12a, 12b and the side faces 12c to 12f in areas adjacent to the end faces 12a, 12b.
[0026] Each of the external electrodes 14A, 14B is composed of one or more electrode layers. The electrode material for each of the external electrodes 14A, 14B can be a metal material such as Ag. In this embodiment, as shown in FIG. 6 , each of the external electrodes 14A, 14B is composed of two electrode layers 15, 16. The first electrode layer 15 is located on the element body 12 side and directly covers the end faces 12a, 12b. The first electrode layer 15 is composed of a baked electrode containing Ag and glass, or a resin electrode. The second electrode layer 16 is located on the outer side and covers the entire surface of the first electrode layer 15. The second electrode layer 16 is composed of a plated electrode. The second electrode layer 16 can be composed of multiple plated layers, and can be composed of three layers (Cu / Ni / Sn) or two layers (Ni / Sn, Ni / Au).
[0027] FIG. 7 shows an element body 12 including an internal electrode 20 that does not include the auxiliary conductors 26 and 28. The through conductors 22 and 24 that constitute the internal electrode 20 in FIG. 7 are joined to the external electrodes 14A and 14B at their end faces 12a and 12b. In the element body 12 shown in FIG. 7, the joint surface S (see FIG. 6) between the internal electrode 20 and the external electrodes 14A and 14B is a region with relatively high electrical resistance. When a predetermined current flows between the external electrodes 14A and 14B, the joint surface S is likely to overheat. In particular, if a defect such as a break occurs in one through conductor (e.g., the through conductor 22), the current equivalent to that of two through conductors flows in the other through conductor (e.g., the through conductor 24). This causes the joint surface S between the other through conductor and the external electrode 14A and 14B to overheat, potentially resulting in meltdown starting from the joint surface S. Breakdown of the through conductor can occur, for example, due to bending or twisting of the through conductor caused by internal stress.
[0028] As shown in FIG. 3 , in the multilayer inductor 10 according to this embodiment, the internal electrode 20 includes auxiliary conductors 26 and 28, which are joined to the external electrodes 14A and 14B at the end faces 12a and 12b. That is, at the end faces 12a and 12b of the internal electrode 20, the through conductors 22 and 24 are joined to the external electrodes 14A and 14B, and the auxiliary conductors 26 and 28 are also joined to the external electrodes 14A and 14B. Therefore, if a malfunction occurs in one of the through conductors, current flows through the remaining through conductors and the auxiliary conductors. As a result, overheating at the joint surfaces S between the remaining through conductors and the external electrodes 14A and 14B is suppressed, and melting starting from the joint surfaces S can be suppressed. Therefore, the multilayer inductor 10 has high reliability.
[0029] In addition, since the joint surface S between the internal electrode 20 and the external electrodes 14A, 14B is enlarged, high connectivity between the internal electrode 20 and the external electrodes 14A, 14B is achieved, and peeling between the internal electrode 20 and the external electrodes 14A, 14B is effectively suppressed.
[0030] Furthermore, the length W1 of the auxiliary conductors 26, 28 in the width direction (first direction) of the element body 12 may be 20 to 50% of the length W of the element body 12 in the first direction.
[0031] Furthermore, the length L1 of the auxiliary conductors 26, 28 in the opposing direction (second direction) of the end faces 12a, 12b may be 2 to 20% of the length L of the element body 12 in the second direction.
[0032] The above-described internal electrode 20 may be composed of a plurality of internal electrodes 20A, 20B as shown in FIG. 8. In this case, the two internal electrodes 20A, 20B shown in FIG. 8 are located between two different layers of the plurality of magnetic layers 19 as shown in FIG. 8. Each internal electrode 20A, 20B has the same shape and dimensions as the above-described internal electrode 20, and includes through conductors 22, 24 and auxiliary conductors 26, 28. Therefore, the through conductor 22 (first through conductor) of the internal electrode 20A and the through conductor 22 (third through conductor) of the internal electrode 20B are aligned along the stacking direction of the element body 12. Similarly, the through conductor 24 (second through conductor) of the internal electrode 20A and the through conductor 24 (fourth through conductor) of the internal electrode 20B are aligned along the stacking direction of the element body 12.
[0033] 8 and 9, if a defect occurs in one of the through conductors, a current flows through the remaining through conductors and also through the auxiliary conductors, thereby preventing overheating at the joint surfaces S between the internal electrodes 20A, 20B and the external electrodes 14A, 14B and preventing melting starting from the joint surfaces S.
[0034] 10, a configuration may also be provided in which an auxiliary conductor 29 extends along the end faces 12a, 12b between the ends 22a, 22b of the through conductor 22 of the internal electrodes 20A, 20B, and an auxiliary conductor 29 extends along the end faces 12a, 12b between the ends 24a, 24b of the through conductor 24 of the internal electrodes 20A, 20B. Each auxiliary conductor 29 extends in the stacking direction of the element body 12 and has, for example, a rectangular column shape. [Explanation of symbols]
[0035] 10... multilayer inductor, 12... element body, 14A, 14B... external electrodes, 19... magnetic layer, 20, 20A, 20B... internal electrodes, 22, 24... through conductors, 26, 28, 29... auxiliary conductors.
Claims
1. an element body including a plurality of stacked magnetic layers and having a pair of end faces facing each other; an internal electrode provided within the element body and extending between the pair of end faces; a pair of external electrodes provided on end surfaces of the element body and joined to the internal electrodes exposed on the end surfaces; Equipped with The internal electrode is a plurality of through conductors extending between the pair of end faces in a direction in which the end faces face each other and having ends exposed at the end faces; a pair of auxiliary conductors each extending between ends of at least one pair of the through conductors among the plurality of through conductors, exposed at the pair of end faces, and joined to the pair of external electrodes at the pair of end faces, respectively; A laminated inductor having the above structure.
2. The multilayer inductor according to claim 1 , wherein the internal electrodes are located between a single layer of the plurality of magnetic layers.
3. The multilayer inductor according to claim 1 , wherein the internal electrodes are located between a plurality of the magnetic layers.
4. The multilayer inductor according to claim 3 , wherein the plurality of through conductors include a pair of through conductors aligned in the stacking direction of the element body.
5. The plurality of through conductors a first through conductor and a second through conductor located between the same magnetic layers; a third through conductor and a fourth through conductor positioned between layers different from the layers between which the first through conductor and the second through conductor are positioned, and aligned with the first through conductor and the second through conductor, respectively, along the stacking direction of the element body; The stacked inductor according to claim 3 , comprising:
6. A multilayer inductor as described in any one of claims 1 to 5, wherein the length of the auxiliary conductor in a first direction perpendicular to the stacking direction of the element body and the opposing direction of the pair of end faces is 20 to 50% of the length of the element body in the first direction.
7. 7. The multilayer inductor according to claim 1, wherein the length of the auxiliary conductor in a second direction parallel to the opposing direction of the pair of end faces is 2 to 20% of the length of the element body in the second direction.
Citation Information
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