Stacked inductor

Abstract

In a laminated inductor, a through conductor provided in a sintered body (sintered body) after sintering is configured to include a pair of lead-out conductors and a pair of internal conductors, and a second end portion of the lead-out conductor overlaps with an end portion of the internal conductor in a stacking direction of the sintered body. Thus, the amount of shrinkage of each conductor at the time of sintering of the sintered body can be reduced, and internal stress generated in the sintered body after sintering can be suppressed.

Description

Technical Field

[0001] This invention relates to multilayer inductors. Background Technology

[0002] Currently, an inductor is known to include a through conductor extending linearly within a body. Japanese Patent Application Publication No. 2020-88289 discloses an inductor comprising a body having a pair of opposite end faces, a through conductor extending flatly between the end faces, and a pair of external electrodes disposed on the two end faces of the body and connected to the through conductor. Summary of the Invention

[0003] The inductor body described in the prior art is a sintered body (sintered body) obtained by firing multiple stacked magnetic layers. The through conductor is obtained by firing a conductive paste coated on the magnetic layers together with the magnetic layers. Generally, the shrinkage rate of the magnetic layers during firing differs from that of the conductive paste. Therefore, internal stress caused by the difference in shrinkage rates is generated within the sintered body, which may lead to cracks caused by internal stress. Through careful research, the inventors have discovered a new technique capable of suppressing cracks caused by internal stress.

[0004] According to one aspect of the present invention, a stacked inductor capable of suppressing cracks is provided.

[0005] A multilayer inductor according to one aspect of the present invention includes: a fired substrate comprising a plurality of stacked layers and having a pair of end faces facing each other in a first direction orthogonal to the stacking direction of the plurality of layers; a through conductor disposed within the fired substrate, extending between the pair of end faces and exposed at two ends on the end faces; a pair of external electrodes disposed on the end faces of the fired substrate and respectively covering the two ends of the through conductor exposed on the end faces, the through conductor comprising: a pair of lead conductors constituting the two ends of the through conductor, having a first end exposed from the end face of the substrate and a second end located inside the substrate; and an internal conductor connecting the pair of lead conductors to each other, having an end overlapping the second end of the lead conductor in the stacking direction of the plurality of layers.

[0006] In the aforementioned multilayer inductor, the through conductor is configured to include a lead conductor and an inner conductor, with the second end of the lead conductor and the end of the inner conductor overlapping in the stacking direction of the substrate. The shrinkage of both the lead conductor and the inner conductor during firing is small, which can suppress internal stress generated within the substrate after firing. Therefore, in the aforementioned multilayer inductor, cracks caused by internal stress can be suppressed.

[0007] In other aspects of the multilayer inductor, the length of the lead conductor in the first direction is shorter than the length of the internal conductor in the first direction.

[0008] Other aspects involve multilayer inductors having a step formed by a second end of an outgoing conductor and an end of an inner conductor that overlaps with the second end.

[0009] In other aspects of the multilayer inductor, the through conductor includes a plurality of inner conductors, each of which extends parallel to a first direction, and adjacent inner conductors in the first direction overlap each other at their ends in the multilayer stacking direction. Attached Figure Description

[0010] Figure 1 This is a perspective view showing the multilayer inductor involved in the implementation method.

[0011] Figure 2 It means Figure 1 A three-dimensional view of the through conductor of the shown body.

[0012] Figure 3 yes Figure 2 The figure shown is a cross-sectional view along line III-III.

[0013] Figure 4 It is a diagram showing the various processes involved in manufacturing the base body.

[0014] Figure 5 It is a diagram showing the various processes involved in manufacturing the base body.

[0015] Figure 6 It is a diagram showing the various processes involved in manufacturing the base body. Detailed Implementation

[0016] Hereinafter, with reference to the accompanying drawings, a mode for carrying out the invention will be described. In the description of the drawings, the same or equivalent elements are referred to by the same reference numerals, and repeated descriptions are omitted.

[0017] Reference Figures 1-3 The structure of the multilayer inductor involved in the embodiment will be described. For example... Figure 1 As shown, the stacked inductor 10 according to the embodiment is configured to include a body 12 and a pair of external electrodes 14A, 14B.

[0018] The body 12 has a generally rectangular parallelepiped shape and a pair of end faces 12a and 12b that face each other in the extending direction of the body 12. The body 12 also has four sides 12c to 12f that extend in the opposite direction of the end faces 12a and 12b and connect the end faces 12a and 12b to each other. Side 12d is the mounting surface that faces the mounting substrate when mounting the multilayer inductor 10, and side 12c, which faces side 12d, becomes the top surface during mounting. Assuming that the dimensions of the end faces 12a and 12b in the opposite direction are length, the dimensions of the sides 12e and 12f in the opposite direction are width, and the dimensions of the sides 12c and 12d in the opposite direction are thickness, as an example, the dimensions of the body 12 are 2.5 mm in length × 2 mm in width × 0.9 mm in thickness.

[0019] The base body 12 has a structure in which a through conductor 20 is disposed inside the magnetic body 18. For example... Figure 3 As shown, the substrate 12 has a stacked structure in which multiple magnetic body layers 19 constituting the magnetic body 18 are stacked in the opposite directions of the side surfaces 12c and 12d. In the following description, the opposite directions of the side surfaces 12c and 12d are also referred to as the stacking direction of the substrate 12, and the opposite directions of the end faces 12a and 12b, which are orthogonal to the stacking direction of the substrate 12, are also referred to as the first direction.

[0020] The magnetic body 18 is made of magnetic materials such as ferrite. The magnetic body 18 is obtained by overlapping multiple unfired magnetic bodies (green sheets or green paste layers) that will become magnetic body layers 19 and then firing them. For example, the number of magnetic body layers 19 constituting the base body 12 is 150 layers. In the actual base body 12, multiple magnetic body layers 19 are integrated to the point that the boundaries between the layers are indistinguishable.

[0021] like Figure 2 and Figure 3 As shown, the through conductor 20 extends between a pair of end faces 12a and 12b. The through conductor 20 is composed of multiple conductors, and in this embodiment is configured to include a pair of lead conductors 21 and 24 and a pair of internal conductors 22 and 23. The through conductor 20 is made of a metallic material. In this embodiment, the through conductor 20 is made of Ag.

[0022] A pair of lead conductors 21 and 24 respectively constitute the two ends of the through conductor 20. More specifically, lead conductor 21 constitutes the end of the through conductor 20 located on the end face 12b, and lead conductor 24 constitutes the end of the through conductor 20 located on the end face 12a. The pair of lead conductors 21 and 24 each have a generally rectangular flat plate shape and extend parallel to the side face 12d. Figure 3As shown, a pair of lead conductors 21 and 24 are located between different layers of the plurality of magnetic layers 19. More specifically, lead conductor 24 is located further away from the side 12d than lead conductor 21.

[0023] As an end in the opposite direction (first direction) of end faces 12a and 12b, lead conductor 21 has a first end 21a exposed from end face 12b and a second end 21b located inside the body 12. Lead conductor 21 is a strip extending along the first direction, and the first end 21a is relatively wide. As an end in the first direction, lead conductor 24 has a first end 24a exposed from end face 12a and a second end 24b located inside the body 12. Lead conductor 24 is a strip extending along the first direction, and the first end 24a is relatively wide.

[0024] As the length in the first direction, the pair of lead conductors 21 and 24 each have a length L. 21 L 24 Length L 21 L 24 All are shorter than the length L of the body 12 in the first direction. The length L of the lead-out conductor 21 is also shorter. 21 The length L of the lead conductor 24 24 They can be the same or different.

[0025] A pair of inner conductors 22 and 23 cooperate to connect a pair of lead conductors 21 and 24 to each other. More specifically, the pair of inner conductors 22 and 23 are arranged from lead conductor 21 toward lead conductor 24, in the order of inner conductor 22, inner conductor 23. Each pair of inner conductors 22 and 23 has a rectangular flat plate shape and extends parallel to its side 12d. Figure 3 As shown, a pair of internal conductors 22 and 23 are located between different layers of the plurality of magnetic layers 19. More specifically, internal conductor 23 is located further away from the side 12d than internal conductor 22.

[0026] As an end in the first direction, the inner conductor 22 has a first end 22a located on the end face 12b side and a second end 22b located on the end face 12a side. Similarly, as an end in the first direction, the inner conductor 23 has a first end 23a located on the end face 12b side and a second end 23b located on the end face 12a side.

[0027] As the length in the first direction, the pair of inner conductors 22 and 23 each have a length L. 22 L 23 Length L 22 L 23 All are shorter than the length L of the body 12 in the first direction. The length L of the internal conductor 22... 22 The length L of the inner conductor 2323 They can be the same or different. Alternatively, the lengths L of the internal conductors 22 and 23 can be... 22 L 23 Designed to be longer than the lead conductors 21 and 24 by length L 21 L 24 long.

[0028] like Figure 3 As shown, the first end 22a of the inner conductor 22 and the second end 21b of the lead-out conductor 21 overlap in the stacking direction of the body 12. More specifically, the first end 22a of the inner conductor 22 overlaps with the second end 21b of the lead-out conductor 21 from the top side (i.e., the side 12c side). Thus, the lead-out conductor 21 and the inner conductor 22 are joined and electrically connected to each other. In addition, a step 25 is formed at the joint between the first end 22a of the inner conductor 22 and the second end 21b of the lead-out conductor 21.

[0029] Furthermore, the second end 23b of the inner conductor 23 overlaps with the second end 24b of the lead-out conductor 24 in the stacking direction of the body 12. More specifically, the second end 23b of the inner conductor 23 overlaps with the second end 24b of the lead-out conductor 24 from the lower side (i.e., the side 12d side). Thus, the lead-out conductor 24 and the inner conductor 23 are joined and electrically connected to each other. In addition, a step 27 is formed at the joint between the second end 23b of the inner conductor 23 and the second end 24b of the lead-out conductor 24.

[0030] Furthermore, the second end 22b of the inner conductor 22 and the first end 23a of the inner conductor 23 overlap in the stacking direction of the body 12. More specifically, the second end 22b of the inner conductor 22 overlaps with the first end 23a of the inner conductor 23 from the lower side (i.e., the side 12d side). Thus, the pair of inner conductors 22 and 23 are joined and electrically connected to each other. In addition, a step 26 is formed at the joint between the second end 22b of the inner conductor 22 and the first end 23a of the inner conductor 23.

[0031] Thus, the through conductor 20 has three steps 25 to 27, and the four conductors 21 to 24 constituting the through conductor 20 are arranged in a stepped manner. The four conductors 21 to 24 gradually move away from the side 12d from the lead conductor 21 toward the lead conductor 24.

[0032] A pair of external electrodes 14A and 14B are respectively disposed on the end faces 12a and 12b of the body 12. External electrode 14A covers the entire area of ​​end face 12a and directly contacts and engages with the end of the through conductor 20 exposed on end face 12a. Similarly, external electrode 14B covers the entire area of ​​end face 12b and directly contacts and engages with the end of the through conductor 20 exposed on end face 12b. In this embodiment, as... Figure 1As shown, each external electrode 14A, 14B integrally covers the end faces 12a, 12b and the side faces 12c to 12f of the region adjacent to the end faces 12a, 12b. Each external electrode 14A, 14B is composed of one or more electrode layers. The electrode material constituting each external electrode 14A, 14B can be, for example, a metallic material such as Ag.

[0033] Next, refer to Figures 4-6 The steps for forming the body 12 containing the through conductor 20 described above will be explained.

[0034] When forming the through conductor 20, firstly, as Figure 4 As shown in (a), a green sheet 18a is prepared to become part of the substrate 12. The green sheet 18 can be composed of one layer or multiple layers. Next, as... Figure 4 As shown in (b), a lead conductor 21 is provided at the edge of the green sheet 18a, which forms the end face 12b of the substrate 12. At this time, the lead conductor 21 is in a conductive paste state and has not yet been fired. For example, the conductive paste is applied by screen printing. Next, as... Figure 4 As shown in (c), a green paste layer 18b is formed by coating the entire rectangular area of ​​the green sheet 18a from the lead conductor 21 to the edge of the end face 12a that becomes the body 12.

[0035] Next, as Figure 5 As shown in (a), an inner conductor 22 is provided on the green paste layer 18b and the second end 21b of the lead conductor 21, with conductive paste applied. The inner conductor 22 is arranged such that its first end 22a overlaps the second end 21b of the lead conductor 21. Next, as... Figure 5 As shown in (b), a green paste layer 18c is formed by coating a green paste layer 18b. More specifically, the green paste layer 18c is integrally formed in a rectangular region from the inner conductor 22 to the edge of the green sheet 18a that forms the end face 12a of the substrate 12. Additionally, a green paste layer 18d is also coated to integrally cover the lead conductor 21. Furthermore, as... Figure 5 As shown in (c), the inner conductor 23 is provided with a conductive paste on the green paste layer 18c and the second end 22b of the inner conductor 22. The inner conductor 23 is provided such that the first end 23a overlaps the second end 22b of the inner conductor 22.

[0036] Next, as Figure 6As shown in (a), a green paste layer 18e is formed by coating a green paste layer 18c. More specifically, the green paste layer 18e is integrally formed in a rectangular region from the inner conductor 23 to the edge of the green sheet 18a that forms the end face 12a of the substrate 12. Additionally, a green paste layer 18f is also integrally formed covering the lead-out conductor 21 and the inner conductor 22. Next, as... Figure 6 As shown in (b), a lead-out conductor 24 is provided with conductive paste on the green paste layer 18e and the second end 23b of the inner conductor 23. The lead-out conductor 24 is provided such that its second end 24b overlaps the second end 23b of the inner conductor 23. Furthermore, as... Figure 6 As shown in (c), a green paste layer 18g is coated to integrally cover the lead conductor 21 and the pair of internal conductors 22, 23. Then, a green paste layer (not shown) is coated to integrally cover the pair of lead conductors 21, 24 and the pair of internal conductors 22, 23 to obtain an unfired body 12.

[0037] Then, the unfired substrate 12 is fired to obtain the substrate 12 described above. Finally, external electrodes 14A and 14B are respectively provided on the end faces 12a and 12b of the substrate 12 to complete the above-described stacked inductor 10.

[0038] As explained above, in the multilayer inductor 10, the through conductor 20 disposed in the fired body 12 (fired body) is configured to include 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 stacking direction of the body 12.

[0039] Adjacent conductors 21-24 are electrically connected at their respective ends, functioning as a single through conductor 20. Furthermore, regarding the relative orientation of the end faces 12a and 12b, compared to the length L of a through conductor formed by a single flat conductor, the length L of each conductor 21-24 is... 21 ~L 24 The length is shortened. This reduces the shrinkage of each conductor 21-24 during the firing of the substrate 12 and suppresses internal stress generated within the substrate 12 after firing. Therefore, in the multilayer inductor 10, cracks caused by internal stress are suppressed.

[0040] In addition, in the multilayer inductor 10, the length L of each of the pair of lead conductors 21 and 24 is... 21 L 24 Designed to be longer than the internal conductors 22 and 23 by a length L 22 L 23Short. In this case, the shrinkage of the lead conductors 21 and 24 during the firing of the substrate 12 can be reduced. Therefore, for example, the situation where the lead conductors 21 and 24 enter the interior of the substrate 12 from the end faces 12a and 12b can be suppressed, and poor connection between the lead conductors 21 and 24 and the external electrodes 14A and 14B can be effectively suppressed.

[0041] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from its spirit. For example, the number of internal conductors in the through conductor is not limited to two, but may be one or more than three. In addition, a pair of lead conductors may be located between the same layer of multiple layers.

Claims

1. A multilayer inductor, characterized in that, include: A fired body comprising multiple stacked layers and having a pair of end faces facing each other in a first direction orthogonal to the stacking direction of the multiple layers; A through conductor disposed within the sintered body, extending throughout the pair of end faces and exposed at both ends on the end faces; and A pair of external electrodes are respectively disposed on the end face of the sintered body, and cover each of the two ends of the through conductor exposed on the end face. The through conductor includes: A pair of lead-out conductors, each constituting one of the two ends of the through conductor, having a first end exposed from the end face of the body and a second end located inside the body; and An inner conductor, which connects the pair of lead conductors to each other, has an end that overlaps and engages with a second end of the lead conductor in the stacking direction of the plurality of layers. The through conductor includes a plurality of the internal conductors. The internal conductors extend parallel to the first direction, respectively. In the first direction, adjacent inner conductors overlap and join each other at their ends in the stacking direction of the plurality of layers.

2. The multilayer inductor as described in claim 1, characterized in that, The length of the lead-out conductor in the first direction is less than the length of the inner conductor in the first direction.

3. The multilayer inductor as described in claim 1 or 2, characterized in that, It has a step formed by the second end of the lead-out conductor and the end of the inner conductor that overlaps with the second end.

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