Multilayer Inductors

Abstract

To provide a multilayer inductor with crack suppression.SOLUTION: In a multilayer inductor 10, a through conductor 20 provided in a fired element body 12 includes a pair of lead conductors 21 and 24 and a pair of inner conductors 22 and 23. Second ends 21b and 24b of the lead conductors 21 and 24 and ends 22a and 23b of the internal conductors 22 and 23 overlap in a stacking direction of the element body 12. As a result, the amount of shrinkage of the lead conductors 21 to 24 during firing of the element body 12 is reduced, and the internal stress generated in the element body 12 after firing is suppressed.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a multilayer inductor. [Background technology]

[0002] Conventionally, inductors having a through conductor that extends linearly within an element body are known. The following Patent Document 1 discloses an inductor that has an element body having a pair of end faces facing each other, a through conductor that extends flat between the end faces, and a pair of external electrodes that are provided on both end faces of the element body and connected to the through conductor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-88289 A Summary of the Invention [Problem to be solved by the invention]

[0004] The inductor element according to the above-mentioned conventional technology is a sintered body (sintered element) obtained by sintering a plurality of stacked magnetic layers. The through conductor is obtained by sintering a conductive paste applied onto the magnetic layer together with the magnetic layer. In general, the shrinkage rate of the magnetic layer and the shrinkage rate of the conductive paste during sintering are different. Therefore, internal stress due to the difference in shrinkage rate occurs in the element after sintering, and cracks due to the internal stress may occur in the element. After extensive research, the inventors have newly discovered a technology that can suppress cracks due to internal stress.

[0005] An object of one aspect of the present invention is to provide a multilayer inductor in which cracks are suppressed. [Means for solving the problem]

[0006] A multilayer inductor according to one aspect of the present invention comprises a sintered body including a plurality of stacked layers and having a pair of end faces facing each other in a first direction perpendicular to the stacking direction of the plurality of layers, a through conductor provided within the sintered body and extending between the pair of end faces with both ends exposed at the end faces, and a pair of external electrodes provided on the end faces of the sintered body respectively and covering both ends of the through conductor exposed at the end faces, the through conductor including a pair of lead conductors constituting both ends of the through conductor and having a first end exposed from the end faces of the body and a second end located inside the body, and an internal conductor connecting the pair of lead conductors together and having an end overlapping with the second end of the lead conductor in the stacking direction of the plurality of layers.

[0007] In the multilayer inductor, the through conductor includes a lead conductor and an internal conductor, and the second end of the lead conductor and the end of the internal conductor overlap in the stacking direction of the element body. The lead conductor and the internal conductor each have a small amount of shrinkage during firing, so that internal stress generated in the element body after firing can be suppressed. Therefore, in the multilayer inductor, cracks caused by internal stress can be suppressed.

[0008] In a multilayer inductor according to another aspect, the length of the lead conductor in the first direction is shorter than the length of the internal conductor in the first direction.

[0009] A multilayer inductor according to another aspect has a step portion formed by a second end portion of the lead conductor and an end portion of the internal conductor overlapping with the second end portion.

[0010] In another aspect of the multilayer inductor, the through conductor has a plurality of internal conductors, each of which extends parallel to a first direction, and adjacent internal conductors in the first direction have ends that overlap each other in the stacking direction of the multiple layers. Effect of the Invention

[0011] According to various aspects of the present invention, a multilayer inductor in which cracks are suppressed is provided. [Brief description of the drawings]

[0012] [Figure 1] 1 is a perspective view showing a multilayer inductor according to an embodiment of the present invention; [Diagram 2] 2 is a perspective view showing a through conductor of the element body shown in FIG. 1. [Diagram 3] 3 is a cross-sectional view of the element body shown in FIG. 2 taken along line III-III. [Figure 4] 3A to 3C are diagrams showing the steps in manufacturing an element body. [Diagram 5] 3A to 3C are diagrams showing the steps in manufacturing an element body. [Figure 6] 3A to 3C are diagrams showing the steps in manufacturing an element body. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same reference numerals are used for the same or equivalent elements, and duplicated explanations will be omitted.

[0014] The configuration of the multilayer inductor according to the embodiment will be described with reference to Figures 1 to 3. As shown in Figure 1, a multilayer inductor 10 according to the embodiment is configured to include an element body 12 and a pair of external electrodes 14A, 14B.

[0015] The element body 12 has a substantially rectangular parallelepiped shape and has 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 opposing direction of the end faces 12a, 12b and connect the end faces 12a, 12b to each other. The side face 12d is a mounting face that faces a mounting substrate when the multilayer inductor 10 is mounted, and the side face 12c that faces the side face 12d becomes a top face when mounted. The dimensions of the element body 12 are, for example, length 2.5 mm × width 2 mm × thickness 0.9 mm, where the dimension in the opposing direction of the end faces 12a, 12b is the length, the dimension in the opposing direction of the side faces 12e, 12f is the width, and the dimension in the opposing direction of the side faces 12c, 12d is the thickness.

[0016] The element body 12 has a configuration in which a through conductor 20 is provided inside the magnetic body 18. As shown in Fig. 3, the element body 12 has a layered structure in which multiple magnetic layers 19 constituting the magnetic body 18 are layered in the opposing direction of the side surfaces 12c, 12d. In the following description, the opposing direction of the side surfaces 12c, 12d is also referred to as the stacking direction of the element body 12, and the opposing direction of the end faces 12a, 12b perpendicular to the stacking direction of the element body 12 is also referred to as the first direction.

[0017] 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 unfired magnetic bodies (green sheets or green paste layers) that will become the magnetic layers 19. The number of magnetic layers 19 that make up the element body 12 is, for example, 150 layers. In the actual element body 12, the multiple magnetic layers 19 are integrated to the extent that the boundaries between the layers are not visible.

[0018] 2 and 3, the through conductor 20 extends between a pair of end faces 12a, 12b. The through conductor 20 is made of a plurality of conductors, and in this embodiment, includes a pair of lead conductors 21, 24 and a pair of internal conductors 22, 23. The through conductor 20 is made of a metal material. In this embodiment, the through conductor 20 is made of Ag.

[0019] The pair of lead conductors 21, 24 constitute both ends of the through conductor 20. More specifically, the lead conductor 21 constitutes the end of the through conductor 20 located on the end face 12b side, and the lead conductor 24 constitutes the end of the through conductor 20 located on the end face 12a side. Each of the pair of lead conductors 21, 24 has a substantially rectangular flat plate shape and extends parallel to the side face 12d. The pair of lead conductors 21, 24 are located between different layers of the multiple magnetic layers 19 as shown in FIG. 3. More specifically, the lead conductor 24 is located farther from the side face 12d than the lead conductor 21.

[0020] The lead conductor 21 has, as its ends in the opposing direction (first direction) of the end faces 12a, 12b, a first end 21a exposed from the end face 12b and a second end 21b located inside the element body 12. The lead conductor 21 has a strip shape extending along the first direction, with the first end 21a being relatively wide. The lead conductor 24 has, as its ends in the first direction, a first end 24a exposed from the end face 12a and a second end 24b located inside the element body 12. The lead conductor 24 has a strip shape extending along the first direction, with the first end 24a being relatively wide.

[0021] The pair of lead conductors 21 and 24 has a length L 21 , L 24 Each has a length L 21 , L 24 Each of the lengths L of the lead conductor 21 is shorter than the length L of the element body 12 in the first direction. 21 and the length L of the lead conductor 24 24 may be the same or different.

[0022] The pair of internal conductors 22, 23 cooperate to connect the pair of lead conductors 21, 24 to each other. More specifically, the pair of internal conductors 22, 23 are arranged in the order of the internal conductor 22 and the internal conductor 23 from the lead conductor 21 to the lead conductor 24. Each of the pair of internal conductors 22, 23 has a rectangular plate shape and extends parallel to the side surface 12d. The pair of internal conductors 22, 23 are located between different layers of the multiple magnetic layers 19 as shown in FIG. 3. More specifically, the internal conductor 23 is located farther from the side surface 12d than the internal conductor 22.

[0023] The internal conductor 22 has, as its ends in the first direction, a first end 22a located on the end face 12b side and a second end 22b located on the end face 12a side. Similarly, the internal conductor 23 has, as its ends in the first direction, a first end 23a located on the end face 12b side and a second end 23b located on the end face 12a side.

[0024] The pair of internal conductors 22 and 23 has a length L22 , L 23 Each has a length L 22 , L 23 Each of the lengths L of the inner conductor 22 is shorter than the length L of the element body 12 in the first direction. 22 and the length L of the inner conductor 23 23 The lengths L of the inner conductors 22 and 23 may be the same or different. 22 , L 23 is the length L of the lead conductors 21 and 24 21 , L 24 It may be designed to be longer than

[0025] 3, the first end 22a of the internal conductor 22 and the second end 21b of the lead conductor 21 overlap in the stacking direction of the element body 12. More specifically, the first end 22a of the internal conductor 22 overlaps the second end 21b of the lead conductor 21 from the upper side (i.e., the side surface 12c side). This allows the lead conductor 21 and the internal conductor 22 to be joined and electrically connected to each other. In addition, a step 25 is formed at the joint between the first end 22a of the internal conductor 22 and the second end 21b of the lead conductor 21.

[0026] Furthermore, the second end 23b of the internal conductor 23 and the second end 24b of the lead conductor 24 overlap in the stacking direction of the element body 12. More specifically, the second end 23b of the internal conductor 23 overlaps the second end 24b of the lead conductor 24 from the lower side (i.e., the side surface 12d side). This allows the lead conductor 24 and the internal conductor 23 to be joined and electrically connected to each other. Furthermore, a step 27 is formed at the joint between the second end 23b of the internal conductor 23 and the second end 24b of the lead conductor 24.

[0027] Furthermore, the second end 22b of the internal conductor 22 and the first end 23a of the internal conductor 23 overlap in the stacking direction of the element body 12. More specifically, the second end 22b of the internal conductor 22 overlaps the first end 23a of the internal conductor 23 from the lower side (i.e., the side surface 12d side). This allows the pair of internal conductors 22, 23 to be joined and electrically connected to each other. In addition, a step 26 is formed at the joint between the second end 22b of the internal conductor 22 and the first end 23a of the internal conductor 23.

[0028] In this way, the through conductor 20 has three steps 25-27, and the four conductors 21-24 constituting the through conductor 20 are arranged in a stepped manner. The four conductors 21-24 are gradually spaced apart from the side surface 12d from the lead conductor 21 to the lead conductor 24.

[0029] A pair of external electrodes 14A, 14B are provided on end faces 12a, 12b of the element body 12, respectively. The external electrode 14A covers the entire area of ​​the end face 12a, and is directly in contact with and joined to the end of the through conductor 20 exposed on the end face 12a. Similarly, the external electrode 14B covers the entire area of ​​the end face 12b, and is directly in contact with and joined to the end of the through conductor 20 exposed on the end face 12b. In this embodiment, as shown in FIG. 1, each of the external electrodes 14A, 14B integrally covers the end faces 12a, 12b and the side faces 12c to 12f in the areas adjacent to the end faces 12a, 12b. Each of the external electrodes 14A, 14B is composed of one or more electrode layers. For example, a metal material such as Ag can be used as the electrode material constituting each of the external electrodes 14A, 14B.

[0030] Next, a procedure for forming the element body 12 including the above-mentioned through conductor 20 will be described with reference to FIGS.

[0031] When forming the through conductor 20, first, as shown in FIG. 4(a), a green sheet 18a that will become a part of the element body 12 is prepared. The green sheet 18a may be composed of one layer or multiple layers. Then, as shown in FIG. 4(b), a lead conductor 21 is provided on the edge of the green sheet 18a that will become the end face 12b of the element body 12. At this time, the lead conductor 21 is in the state of a conductive paste and has not yet been fired. The conductive paste is applied, for example, by a screen printing method. Next, as shown in FIG. 4(c), a green paste layer 18b is applied and formed on the entire rectangular area on the green sheet 18a from the lead conductor 21 to the edge of the green sheet 18a that will become the end face 12a of the element body 12.

[0032] Next, as shown in FIG. 5(a), an internal conductor 22 in a conductive paste state is provided on the green paste layer 18b and the second end 21b of the lead conductor 21. The internal conductor 22 is provided so that a first end 22a overlaps the second end 21b of the lead conductor 21. Next, as shown in FIG. 5(b), a green paste layer 18c is applied and formed on the green paste layer 18b. More specifically, the green paste layer 18c is provided over the entire rectangular region from the internal conductor 22 to the edge of the green sheet 18a that becomes the end face 12a of the element body 12. A green paste layer 18d that entirely covers the lead conductor 21 is also applied and formed. Furthermore, as shown in FIG. 5(c), an internal conductor 23 in a conductive paste state is provided on the green paste layer 18c and the second end 22b of the internal conductor 22. The internal conductor 23 is provided so that a first end 23a overlaps the second end 22b of the internal conductor 22.

[0033] Next, as shown in FIG. 6(a), a green paste layer 18e is applied on the green paste layer 18c. More specifically, the green paste layer 18e is provided over the entire rectangular region from the internal conductor 23 to the edge of the green sheet 18a that is the end face 12a of the element body 12. A green paste layer 18f that integrally covers the lead conductor 21 and the internal conductor 22 is also applied. Next, as shown in FIG. 6(b), a lead conductor 24 in the form of a conductive paste is provided on the green paste layer 18e and the second end 23b of the internal conductor 23. The lead conductor 24 is provided so that the second end 24b overlaps the second end 23b of the internal conductor 23. Furthermore, as shown in FIG. 6(c), a green paste layer 18g that integrally covers the lead conductor 21 and the pair of internal conductors 22, 23 is applied. Then, a green paste layer (not shown) is applied to integrally cover the pair of lead conductors 21, 24 and the pair of internal conductors 22, 23, to obtain an unfired element body 12.

[0034] Thereafter, the unsintered element 12 is subjected to a sintering process to obtain the above-mentioned element 12. Finally, external electrodes 14A, 14B are provided on end faces 12a, 12b of the element 12, respectively, to complete the above-mentioned layered inductor 10.

[0035] As described above, in the layered inductor 10, the through conductor 20 provided in the sintered element body 12 (sintered element body) is composed of a pair of lead conductors 21, 24 and a pair of internal conductors 22, 23, and the second ends 21b, 24b of the lead conductors 21, 24 and the ends 22a, 23b of the internal conductors 22, 23 overlap in the layering direction of the element body 12.

[0036] Adjacent conductors 21 to 24 are electrically connected to each other at their respective ends, and function as a through conductor 20 as a whole. In addition, in the opposing direction of the end faces 12a and 12b, the length L of each of the conductors 21 to 24 is longer than the length L of the through conductor when it is configured as a single flat conductor. 21 ~L 24The length of each conductor 21-24 is shortened. This reduces the amount of shrinkage of each conductor 21-24 when element body 12 is fired, and suppresses internal stress generated in element body 12 after firing. Therefore, in multilayer inductor 10, cracks caused by internal stress are suppressed.

[0037] In the multilayer inductor 10, the length L 21 , L 24 is the length L of the inner conductors 22 and 23. 22 , L 23 In this case, the amount of shrinkage of the lead conductors 21, 24 during firing of the element body 12 is reduced. This reduces the possibility of the lead conductors 21, 24 penetrating into the element body 12 from the end faces 12a, 12b, and effectively prevents poor connection between the lead conductors 21, 24 and the external electrodes 14A, 14B.

[0038] Although the embodiments of the present invention have been described above, the present invention is not necessarily limited to the above-mentioned embodiments, and various modifications are possible within the scope of the gist of the present invention. For example, the number of internal conductors of the through conductor is not limited to two, and may be one, three or more. In addition, a pair of lead conductors may be located between the same layers of multiple layers. [Explanation of symbols]

[0039] 10... multilayer inductor, 12... element body, 14A, 14B... external electrodes, 19... magnetic layer, 20... through conductor, 21, 24... lead conductor, 22, 23... internal conductor, 25-27... stepped portion.

Claims

1. A sintered body including a plurality of stacked layers and having a pair of end faces facing each other in a first direction perpendicular to a stacking direction of the plurality of layers; a through conductor provided within the sintered body, extending between the pair of end faces and having both ends exposed at the end faces; a pair of external electrodes provided on end surfaces of the sintered body and covering both ends of the through conductor exposed on the end surfaces; Equipped with The through conductor is a pair of lead conductors each constituting both ends of the through conductor, the lead conductors having a first end exposed from an end face of the sintered body and a second end located inside the sintered body; an internal conductor that connects the pair of lead conductors to each other and has an end that directly contacts and overlaps with a second end of the lead conductor in the stacking direction of the plurality of layers; Including, The through conductor comprises a plurality of the inner conductors, Each of the internal conductors extends parallel to the first direction, Ends of the internal conductors adjacent to each other in the first direction are in direct contact with each other and overlap each other in a stacking direction of the plurality of layers, A multilayer inductor, wherein the internal conductor and the lead conductor constituting the through conductor are arranged in a stepped manner, and the positions of the pair of lead conductors in relation to the stacking direction of the multiple layers are different.

2. The multilayer inductor according to claim 1 , wherein a length of the lead conductor in the first direction is shorter than a length of the internal conductor in the first direction.

3. 3. The multilayer inductor according to claim 1, further comprising a step formed by the second end of the lead conductor and an end of the internal conductor overlapping the second end.

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