Multilayer varistor

Abstract

To provide a multilayer varistor with small variation in an electrostatic capacitance.SOLUTION: A multilayer varistor comprises: a first internal electrode projection part (26) that is extended toward a first end surface (13) from a third internal electrode (23) to between a first side surface (17) and a first varistor region (24) in a lamination direction; and a second internal electrode projection part (27) that is extended to a second end surface (15) from the third internal electrode (23) between the first side surface (17) and a second varistor region (25).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a multilayer varistor used in various electronic devices. [Background technology]

[0002] In recent years, home appliances and in-vehicle electronic devices have become smaller, and varistors, which are components of these devices, are also required to be smaller. In addition, high-frequency electric signals are used in home appliances and in-vehicle electronic devices. As electric signals become higher in frequency, the capacitance of the varistor affects the performance of home appliances and in-vehicle electronic devices. Therefore, there is a demand for varistors that have a small capacitance and small capacitance variation while maintaining a predetermined varistor voltage. In addition, when using varistors in pairs, a proposal has been made to form two varistors in one element in order to reduce the difference in capacitance between the pair. As an example of a technical document related to this conventional varistor, Patent Document 1 is known. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2018 / 0226194 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional varistors, stray capacitance occurs not only between the internal electrodes that exert varistor performance, but also between the internal electrodes and other external electrodes, which makes the capacitance prone to variation due to variations in the external electrodes in particular. [Means for solving the problem]

[0005] In view of the above problems, the laminated varistor of the present disclosure has the following configuration. That is, the laminated varistor of the present disclosure includes a sintered body, a first external electrode, a second external electrode, a third external electrode, a fourth external electrode, a first internal electrode, a second internal electrode, a third internal electrode, a first varistor region, a second varistor region, a first internal electrode protrusion, and a second internal electrode protrusion. The sintered body has a varistor layer. The sintered body is formed by stacking and firing the varistor layers. The sintered body has a rectangular parallelepiped shape. The sintered body further has a first side surface, a second side surface, a first end surface, and a second end surface. The first side surface is arranged along the longitudinal direction of the rectangular parallelepiped. The second side surface is arranged parallel to the first side surface. The second side surface is arranged at a position sandwiching the rectangular parallelepiped when viewed from the first side surface. The first end face is disposed perpendicular to the longitudinal direction of the rectangular parallelepiped. The second end face is disposed parallel to the first end face. The second end face is disposed at a position sandwiching the rectangular parallelepiped when viewed from the first end face. The first external electrode is provided on the first end face. The second external electrode is provided on the second end face. The third external electrode is provided on the second side face. The first internal electrode is provided inside the sintered body. The first internal electrode is electrically connected to the first external electrode. The second internal electrode is provided inside the sintered body. The second internal electrode is electrically connected to the second external electrode. The third internal electrode is provided inside the sintered body. The third internal electrode is electrically connected to the third external electrode and the fourth external electrode. In the first varistor region, the first internal electrode and the third internal electrode overlap in the stacking direction via a varistor layer. In the second varistor region, the second internal electrode and the third internal electrode overlap in the stacking direction with the varistor layer interposed between them. The first internal electrode projection is located between the first side surface and the first varistor region in the stacking direction. The first internal electrode projection extends from the third internal electrode toward the first end face in the stacking direction. The second internal electrode projection is located between the first side surface and the second varistor region in the stacking direction. The second internal electrode projection extends from the third internal electrode toward the second end face in the stacking direction. Effect of the Invention

[0006] With the above-described configuration, the laminated varistor of the present disclosure can reduce the variation in stray capacitance due to the variation in the external electrodes, and therefore the laminated varistor of the present disclosure can reduce the variation in capacitance between varistor pairs. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view of a laminated varistor according to an embodiment of the present disclosure; [Diagram 2] FIG. 1 is a perspective view of a laminated varistor according to an embodiment of the present disclosure. [Diagram 3] 1 is a cross-sectional view of a laminated varistor according to an embodiment of the present disclosure; [Figure 4] FIG. 1 is a perspective view of a laminated varistor according to a modified example of an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, a laminated varistor according to an embodiment of the present disclosure will be described with reference to the drawings.

[0009] FIG. 1 is a perspective view of a laminated varistor according to an embodiment of the present disclosure, FIG. 2 is a perspective view of the laminated varistor from the lamination direction, and FIG. 3 is a cross-sectional view of the laminated varistor cut along a plane passing through line III-III in FIG. 1. In each figure, an xyz orthogonal coordinate system is defined with the length direction of the sintered body 12 as the x-axis, the width direction as the y-axis, and the height direction as the z-axis. The height direction coincides with the lamination direction of the varistor layer 11. In each figure, not only the diagram related to the laminated varistor but also the xyz coordinate system is illustrated. The sintered body 12 of this laminated varistor excluding the external electrodes has a rectangular parallelepiped shape with a length of 1.6 mm, a width of 0.8 mm, and a height of 0.6 mm.

[0010] The sintered body 12 is formed by stacking and sintering the varistor layers 11. The sintered body 12 has a first end face 13, a second end face 15, a first side face 17, a second side face 18, a bottom face 28, and a top face 29. The first side face 17 is arranged along the longitudinal direction of the rectangular parallelepiped, i.e., the length direction of the sintered body 12. The second side face 18 is arranged parallel to the first side face 17 and at a position that sandwiches the rectangular parallelepiped when viewed from the first side face 17. The first end face 13 is arranged perpendicular to the longitudinal direction of the rectangular parallelepiped. The second end face 15 is arranged parallel to the first end face 13 and at a position that sandwiches the rectangular parallelepiped when viewed from the first end face 13.

[0011] The first end face 13 and the second end face 15 are parallel to the yz plane. The first side face 17 and the second side face 18 are parallel to the xz plane. The bottom face 28 and the top face 29 are parallel to the xy plane. The plane passing through the line III-III shown in FIG. 1 is parallel to the xz plane.

[0012] The varistor layer 11 constituting the sintered body 12 is mainly composed of ZnO, and the secondary components are Bi2O3, Co2O3, MnO2, Sb2O3, or Pr6O 11, Co2O3, CaCO3, Cr2O3, etc. The sintered body 12 is formed by sintering ZnO and precipitating other subcomponents at its grain boundaries. In the sintered body 12, a first internal electrode 21, a second internal electrode 22, and a third internal electrode 23 are formed between each of the stacked varistor layers 11. More specifically, as shown in the cross-sectional structure of FIG. 3, the sintered body 12 has a structure in which six varistor layers 11, that is, a first varistor layer 11a, a second varistor layer 11b, a third varistor layer 11c, a fourth varistor layer 11d, a fifth varistor layer 11e, and a sixth varistor layer 11f are stacked in this order. A first internal electrode 21 and a second internal electrode 22 are provided between the first varistor layer 11a and the second varistor layer 11b. In addition, a third internal electrode 23 is provided between the second varistor layer 11b and the third varistor layer 11c. A first internal electrode 21 and a second internal electrode 22 are provided between the third varistor layer 11c and the fourth varistor layer 11d. A third internal electrode 23 is provided between the fourth varistor layer 11d and the fifth varistor layer 11e. A first internal electrode 21 and a second internal electrode 22 are provided between the fifth varistor layer 11e and the sixth varistor layer 11f. The surface of the first varistor layer 11a opposite to the surface on which the second varistor layer 11b is arranged coincides with the lower surface 28. Moreover, the surface of the sixth varistor layer 11f opposite to the surface on which the fifth varistor layer 11e is arranged coincides with the upper surface 29.

[0013] A first external electrode 14 is provided on the first end face 13 of the sintered body 12. The first external electrode 14 is provided across a part of the first side face 17, a part of the second side face, a part of the lower face 28, and a part of the upper face 29. The first external electrode 14 is electrically connected to the first internal electrode 21. A second external electrode 16 is provided on the second end face 15. The second external electrode 16 is provided across a part of the first side face 17, a part of the second side face, a part of the lower face 28, and a part of the upper face 29. The second external electrode 16 is electrically connected to the second internal electrode 22. A third external electrode 19 is provided on the first side face 17. The third external electrode 19 is provided across a part of the lower face 28 and a part of the upper face 29. The third external electrode 19 is electrically connected to the third internal electrode 23. A fourth external electrode 20 is provided on the second side face 18. The fourth external electrode 20 is provided across a part of the lower surface 28 and a part of the upper surface 29. The fourth external electrode 20 is electrically connected to the third internal electrode 23.

[0014] A first varistor region 24 is formed by a part of the first internal electrode 21 and a part of the third internal electrode 23 facing each other in the stacking direction. A second varistor region 25 is formed by a part of the second internal electrode 22 and a part of the third internal electrode 23 facing each other in the stacking direction.

[0015] The sintered body 12 further has a first internal electrode projection 26 and a second internal electrode projection 27 .

[0016] When the sintered body 12 is viewed from the stacking direction of the varistor layer 11 (the positive direction of the z-axis), the first internal electrode protrusion 26 is arranged between the first side surface 17 and the first varistor region 24 as shown in Figure 2, and extends in a direction from the third internal electrode 23 toward the first end face 13.

[0017] The point on the first varistor region 24 that is closest to the first end face 13 is designated as point P. Additionally, the point on the third external electrode 19 that is closest to the first end face 13 is designated as point Q. A part of the first internal electrode projection 26, i.e., a part of its tip portion 26s, extends to a position closer to the first end face 13 than the line connecting points P and Q (line segment PQ shown by a dashed line in FIG. 2).

[0018] When the sintered body 12 is viewed from the positive direction of the z-axis, the second internal electrode protrusion 27 is positioned between the first side surface 17 and the second varistor region 25 as shown in Figure 2, and extends in a direction from the third internal electrode 23 toward the second end face 15.

[0019] The point of the second varistor region 25 that is closest to the second end face 15 is designated as point T. Moreover, the point of the third external electrode 19 that is closest to the second end face 15 is designated as point U. A part of the second internal electrode projection 27, i.e., a part of its tip portion 27s, extends to a position closer to the second end face 15 than the line connecting points T and U (line segment TU shown by a dashed line in FIG. 2).

[0020] By providing the first internal electrode projection 26 in this manner, the first internal electrode projection 26 straddles the line segment PQ. Therefore, even if the shape of the third external electrode 19 varies, there is no variation in the stray capacitance between the first varistor region 24 and the third external electrode 19. Furthermore, by providing the second internal electrode projection 27, the second internal electrode projection 27 straddles the line segment TU. Therefore, even if the shape of the third external electrode 19 varies, there is no variation in the stray capacitance between the second varistor region 25 and the third external electrode 19.

[0021] In this manner, it is possible to reduce the variation in stray capacitance of the multilayer varistor caused by the variation in the shape of the third external electrode 19, and as a result, it is possible to reduce the variation in capacitance between pairs.

[0022] (Modification) A perspective view of a laminated varistor according to a modified example of an embodiment of the present disclosure is shown in Fig. 4. Since the configuration, appearance and cross section of this modified example are similar to those of the laminated varistor of the above embodiment shown in Fig. 1 and Fig. 3, detailed description of overlapping parts will be avoided, and only differences from the laminated varistor of the above embodiment will be described.

[0023] 4, the tip 26s of the first internal electrode projection 26 extends so as to be at the same position as the closest position to the first end face 13 of the first varistor region 24 or closer to the first end face 13 than that. Moreover, the tip 27s of the second internal electrode projection 27 extends so as to be at the same position as the closest position to the second end face 15 of the second varistor region 25 or closer to the second end face 15 than that. In this way, the variation in stray capacitance due to the variation in the shape of the third external electrode 19 can be further reduced.

[0024] However, when the sintered body 12 is viewed from the stacking direction, it is preferable that the first external electrode 14 and the first internal electrode projection 26, and the second external electrode 16 and the second internal electrode projection 27 do not overlap each other. By doing so, it is possible to reduce the stray capacitance generated between the first external electrode 14 and the first internal electrode projection 26, or between the second external electrode 16 and the second internal electrode projection 27.

[0025] (Desired example) More preferable examples of the above embodiment and its modifications will be described below.

[0026] It is desirable that the first internal electrode 21 and the second internal electrode 22 are formed in the same layer. With this configuration, efficient production can be achieved.

[0027] When the sintered body 12 is viewed in the stacking direction, it is desirable that the length of the first internal electrode protrusion 26 and the second internal electrode protrusion 27 in the y-axis direction be 5% or more and 20% or less of the length of the first end face 13 in the y-axis direction. This will be described with reference to FIG. 2. In FIG. 2, let the length of the first end face 13 in the y-axis direction be Ly, and the length of the protrusion of the first internal electrode protrusion 26 in the y-axis direction be W26. Note that the length of the protrusion of the second internal electrode protrusion 27 in the y-axis direction is equal to the length of the protrusion of the first internal electrode protrusion 26 in the y-axis direction (W26). At this time, it is desirable that 0.05Ly ≤ W26 ≤ 0.2Ly.

[0028] If W26 < 0.05Ly, the effect of the internal electrode protrusion will be reduced. Also, if 0.2Ly < W26, the capacitance between the third internal electrode 23 and the first external electrode 14 and the second external electrode 16 will increase.

[0029] Also, the gap in the y-axis direction between the first internal electrode protrusion 26 and the first varistor region 24 is preferably 10% or more and 30% or less of the length of the first end face 13 in the y-axis direction. This will be described with reference to FIG. 2. In FIG. 2, if the gap in the y-axis direction between the first internal electrode protrusion 26 and the first varistor region 24 is Wg, it is desirable that 0.1Ly ≤ Wg ≤ 0.3Ly. If Wg < 0.1Ly, since the distance between the first varistor region 24 and the first internal electrode protrusion 26 is short, the effect of suppressing the variation in parasitic capacitance will be reduced. Note that the same applies to the second internal electrode protrusion 27 as to the first internal electrode protrusion 26.

[0030] Note that the shape of the tip 26s of the first internal electrode protrusion 26 and the tip 27s of the second internal electrode protrusion 27 may be any shape, but a rectangular shape is the most effective.

[0031] (Aspect) Embodiments of the present disclosure will be described below.

[0032] The laminated varistor according to the first aspect of the present disclosure comprises a sintered body (12), a first external electrode (14), a second external electrode (16), a third external electrode (19), a fourth external electrode (20), a first internal electrode (21), a second internal electrode (22), a third internal electrode (23), a first varistor region (24), a second varistor region (25), a first internal electrode protrusion (26), and a second internal electrode protrusion (27).

[0033] The sintered body (12) has a varistor layer (11). The sintered body (12) is formed by stacking the varistor layers (11) and firing them. The sintered body (12) has a rectangular parallelepiped shape. The sintered body (12) also has a first side surface (17), a second side surface (18), a first end surface (13), and a second end surface (15).

[0034] The first side surface (17) is disposed along the longitudinal direction of the rectangular parallelepiped. The second side surface (18) is disposed parallel to the first side surface (17). The second side surface (18) is disposed at a position that sandwiches the rectangular parallelepiped when viewed from the first side surface (17). The first end surface (13) is disposed perpendicular to the longitudinal direction of the rectangular parallelepiped. The second end surface (15) is disposed parallel to the first end surface (13). The second end surface (15) is disposed at a position that sandwiches the rectangular parallelepiped when viewed from the first end surface (13).

[0035] The first external electrode (14) is provided on the first end face (13). The second external electrode (16) is provided on the second end face (15). The third external electrode (19) is provided on the first side face (17). The fourth external electrode (20) is provided on the second side face (18).

[0036] The first internal electrode (21) is provided inside the sintered body (12). The first internal electrode (21) is electrically connected to the first external electrode (14). The second internal electrode (22) is provided inside the sintered body (12). The second internal electrode (22) is electrically connected to the second external electrode (16). The third internal electrode (23) is provided inside the sintered body (12). The third internal electrode (23) is electrically connected to the third external electrode (19) and the fourth external electrode (20).

[0037] The first varistor region (24) is formed by the first internal electrode (21) and the third internal electrode (23) overlapping in the stacking direction of the varistor layer (11). The second varistor region (25) is formed by the second internal electrode (22) and the third internal electrode (23) overlapping in the stacking direction.

[0038] The first internal electrode projection (26) is located between the first side surface (17) and the first varistor region (24) when the sintered body (12) is viewed from the stacking direction. Moreover, the first internal electrode projection (26) extends from the third internal electrode (23) toward the first end face (13) when the sintered body (12) is viewed from the stacking direction. The first internal electrode projection (26) extends to the first end face (13) side beyond a line (PQ) connecting a point (P) of the first varistor region (24) closest to the first end face (13) and a point (Q) of the third external electrode (19) closest to the first end face (13).

[0039] The second internal electrode projection (27) is located between the first side surface (17) and the second varistor region (25) when the sintered body (12) is viewed from the stacking direction. Moreover, the second internal electrode projection (27) extends from the third internal electrode (23) toward the second end face (15) when the sintered body (12) is viewed from the stacking direction. The second internal electrode projection (27) extends to the second end face (15) side beyond a line (TU) connecting a point (T) of the second varistor region (25) closest to the second end face (15) and a point (U) of the third external electrode (19) closest to the second end face (15).

[0040] According to this embodiment, by providing the first internal electrode projection (26), the first internal electrode projection (26) straddles the line (PQ). Therefore, even if the shape of the third external electrode (19) varies, the stray capacitance between the first varistor region (24) and the third external electrode (19) does not vary. Furthermore, by providing the second internal electrode projection (27), the second internal electrode projection (27) straddles the line (TU). Therefore, even if the shape of the third external electrode (19) varies, the stray capacitance between the second varistor region (25) and the third external electrode (19) does not vary.

[0041] In this way, it is possible to reduce the variation in stray capacitance of the laminated varistor caused by the variation in the shape of the third external electrode (19), and as a result, it is possible to reduce the variation in capacitance between pairs.

[0042] The laminated varistor according to the second aspect of the present disclosure is the laminated varistor according to the first aspect, wherein the tip portion (26s) of the first internal electrode projection (26) extends to a position equal to or closer to the first end face (13) than the point of the first varistor region (24) closest to the first end face (13), and the tip portion (27s) of the second internal electrode projection (27) extends to a position equal to or closer to the second end face (15) than the point of the second varistor region (25) closest to the second end face (15).

[0043] According to this embodiment, the variation in stray capacitance caused by the variation in the shape of the third external electrode 19 can be further reduced.

[0044] The laminated varistor according to the third embodiment of the present disclosure is the laminated varistor according to the first or second embodiment, and has the following configuration. The direction perpendicular to the first end face (13) and the second end face (15) is defined as the x-axis, and the direction perpendicular to the first side face (17) and the second side face (18) is defined as the y-axis. In this case, the length of the first internal electrode projection (26) and the second internal electrode projection (27) in the y-axis direction is 5% to 20% of the length of the first end face (13) of the sintered body (12) in the y-axis direction. In addition, the gap in the y-axis direction between the first internal electrode projection (26) and the first varistor region (24) is 10% to 30% of the length of the first end face (13) in the y-axis direction. [Industrial Applicability]

[0045] INDUSTRIAL APPLICABILITY The laminated varistor according to the present disclosure is capable of reducing the variation in stray capacitance caused by the variation in the positions of the external electrodes, and is therefore industrially useful. [Explanation of symbols]

[0046] 11 Varistor layer 11a First varistor layer 11b Second Varistor Layer 11c Third Varistor Layer 11d Fourth Varistor Layer 11e 5th Ballista Layer 11f 6th varistor layer 12 Sintered body 13 First end face 14 First external electrode 15 Second end face 16 Second external electrode 17 First aspect 18 The second aspect 19 Third external electrode 20 Fourth external electrode 21 First internal electrode 22 Second internal electrode 23 Third inner electrode 24 First Varistor Area 25 Second Varistor Region 26 First internal electrode protrusion 26s and 27s tip parts 27 second internal electrode protrusion 28 bottom surface 29 top surface

Claims

1. The sintered body has a rectangular parallelepiped shape and includes a plurality of varistor layers stacked in a stacking direction, the sintered body is a laminated varistor having a first side surface arranged along the longitudinal direction of the rectangular parallelepiped, a second side surface arranged at a position opposite to the first side surface, a first end surface arranged at a position between the first side surface and the second side surface, and a second end surface arranged at a position opposite to the first end surface, a first external electrode provided on the first end surface; a second external electrode provided on the second end surface; a third external electrode provided on the first side surface; a fourth external electrode provided on the second side surface; a first internal electrode provided inside the sintered body and electrically connected to the first external electrode; a second internal electrode provided inside the sintered body and electrically connected to the second external electrode; a third internal electrode provided inside the sintered body and electrically connected to the third external electrode and the fourth external electrode; a first varistor region in which the first internal electrode and the third internal electrode overlap each other in the stacking direction via the varistor layer; a second varistor region in which the second internal electrode and the third internal electrode overlap each other in the stacking direction via the varistor layer; In the stacking direction, a first internal electrode protrusion extending from the third internal electrode toward the first end face between the first side surface and the first varistor region; a second internal electrode protrusion extending from the third internal electrode toward the second end face between the first side surface and the second varistor region, Multilayer varistor.

2. a length between a tip of the first internal electrode projection and a tip of the second internal electrode projection in the longitudinal direction is longer than a length of the third external electrode; The multilayer varistor according to claim 1.

3. In the stacking direction, the first internal electrode projection and the second internal electrode projection do not overlap with the first internal electrode and the second internal electrode. The multilayer varistor according to claim 1.

4. In the stacking direction, a first internal electrode protrusion extending from the third internal electrode toward the first end face between the second side surface and the first varistor region; a second internal electrode protrusion extending from the third internal electrode toward the second end face between the second side surface and the second varistor region; The multilayer varistor according to claim 1.

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