Transient voltage protection device

Abstract

To provide a transient voltage protection characteristic device capable of suppressing deterioration of transient voltage protection characteristics.SOLUTION: A transient voltage protection device includes an element body 2, a first external electrode disposed on a surface of the element body 2, a second external electrode disposed on the surface of the element body 2 and separated from the first external electrode, an internal electrode 5, and an internal electrode 6. The internal electrode 5 is disposed in the element body 2 and is connected to the first external electrode. The internal electrodes 6 face the internal electrodes 5 in the element body 2 and are connected to the second external electrode. The internal electrodes 5 include ends exposed to the surfaces of the element body 2 and connected to the first external electrodes, and an end 5f located in the element body 2 and separated from the surfaces of the element body 2. The end 5f includes a corner portion 51 including an edge 51a facing the internal electrodes 6. The edge 51a is curved in a plan view of the internal electrodes 5.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a transient voltage protection device. [Background technology]

[0002] A known transient voltage protection device includes an element body, a pair of external electrodes, and a pair of internal electrodes (see, for example, Patent Document 1). The pair of external electrodes are arranged on the surface of the element body and are spaced apart from each other. The pair of internal electrodes face each other within the element body and are connected to corresponding ones of the pair of external electrodes. Each of the pair of internal electrodes has a rectangular shape in a plan view of the internal electrode. Each of the pair of internal electrodes includes a first end exposed on the surface of the element body and connected to the corresponding external electrode, and a second end located within the element body and away from the surface of the element body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2014 / 98084 Summary of the Invention [Problem to be solved by the invention]

[0004] In the transient voltage protection device described above, discharge occurs between a pair of opposing internal electrodes. When each of the pair of internal electrodes has a rectangular shape in a plan view of the internal electrodes, the electric field tends to concentrate at the second end, and the discharge tends to concentrate locally. For example, the electric field tends to concentrate at a corner of the second end. When the discharge concentrates locally, the transient voltage protection characteristics may be degraded.

[0005] An object of one aspect of the present invention is to provide a transient voltage protection device that can suppress degradation of transient voltage protection characteristics. [Means for solving the problem]

[0006] A transient voltage protection device according to one embodiment comprises an element body, a first external electrode, a second external electrode, a first internal electrode, and a second internal electrode. The first external electrode is disposed on the surface of the element body. The second external electrode is disposed on the surface of the element body and spaced apart from the first external electrode. The first internal electrode is disposed within the element body and connected to the first external electrode. The second internal electrode faces the first internal electrode within the element body and is connected to the second external electrode. The first internal electrode includes a first end exposed on the surface of the element body and connected to the first external electrode, and a second end located within the element body and away from the surface of the element body. The second ends are a pair of corners adjacent to each other in the direction in which the first internal electrode and the second internal electrode face each other, including a first corner including an edge facing the second internal electrode and a second corner farther from the second internal electrode than the first corner. The edge included in the first corner is curved in a plan view of the first internal electrode.

[0007] In the above-described one aspect, the edge included in the first corner portion is curved in a plan view of the first internal electrode. Therefore, a location where an electric field is likely to concentrate at the second end is unlikely to occur, and discharge is unlikely to concentrate locally. As a result, the above-described one aspect can suppress deterioration of transient voltage protection characteristics. [Effects of the Invention]

[0008] One aspect of the present invention provides a transient voltage protection device that can suppress degradation of the transient voltage protection characteristics. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view illustrating a transient voltage protection device according to one embodiment. [Figure 2] FIG. 2 is an exploded perspective view showing the configuration of the element body. [Figure 3] FIG. 3 is a plan view showing the configuration of the internal electrodes and the discharge auxiliary parts. [Figure 4] FIG. 4 is a diagram showing a cross-sectional configuration of the transient voltage protection device according to this embodiment. [Figure 5] FIG. 5 is a plan view showing the configuration of the internal electrodes. [Figure 6] FIG. 6 is a plan view showing the configuration of the internal electrodes. [Figure 7] FIG. 7 is a plan view showing the configuration of the internal electrodes. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same elements or elements having the same functions will be denoted by the same reference numerals, and redundant description will be omitted.

[0011] The configuration of a transient voltage protection device 1 according to this embodiment will be described with reference to Figs. 1 to 5. Fig. 1 is a perspective view showing the transient voltage protection device according to this embodiment. Fig. 2 is an exploded perspective view showing the configuration of the element body. Fig. 3 is a plan view showing the configuration of the internal electrodes and discharge auxiliary section. Fig. 4 is a diagram showing the cross-sectional configuration of the transient voltage protection device according to this embodiment. Fig. 5 is a plan view showing the configuration of the internal electrodes.

[0012] As shown in FIGS. 1 and 2, the transient voltage protection device 1 includes an element body 2, a pair of external electrodes 3 and 4, a pair of internal electrodes 5 and 6, and a discharge auxiliary section 7. The transient voltage protection device 1 is mounted in an electronic device (not shown). The transient voltage protection device 1 protects the electronic device from transient voltages. The electronic device protected by the transient voltage protection device 1 includes, for example, a circuit board or an electronic component. The transient voltage is caused, for example, by electrostatic discharge (ESD).

[0013] The element body 2 has a rectangular parallelepiped shape. Examples of rectangular parallelepiped shapes include a rectangular parallelepiped shape with chamfered corners and ridges, and a rectangular parallelepiped shape with rounded corners and ridges. The element body 2 includes a pair of end faces 2a, 2b facing each other, a pair of side faces 2c, 2d facing each other, and a pair of side faces 2e, 2f facing each other. In this embodiment, the pair of end faces 2a, 2b face each other in a first direction D1, the pair of side faces 2e, 2f face each other in a second direction D2, and the pair of side faces 2c, 2d face each other in a third direction D3. The first direction D1, the second direction D2, and the third direction D3 intersect with each other, for example. In this embodiment, the first direction D1, the second direction D2, and the third direction D3 are perpendicular to each other.

[0014] The surface of the element body 2 includes a pair of end faces 2a, 2b and four side faces 2c, 2d, 2e, and 2f. The four side faces 2c, 2d, 2e, and 2f are adjacent to the end face 2a and the end face 2b, respectively, and extend in the first direction D1 to connect the end faces 2a and 2b. One of the four side faces 2c, 2d, 2e, and 2f is defined as a mounting surface that faces an electronic device in which the transient voltage protection device 1 is mounted.

[0015] As shown in Fig. 2, the element body 2 is configured by stacking multiple insulator layers 20 in the third direction D3. The element body 2 includes multiple stacked insulator layers 20. In the element body 2, the insulator layers 20 are integrated to the extent that the boundaries between the insulator layers 20 are not visible. Each insulator layer 20 is configured, for example, as a sintered body of a ceramic green sheet containing an insulating material.

[0016] The insulator material includes, for example, a ceramic material. The ceramic material is, for example, selected from the group consisting of Fe2O3, NiO, CuO, ZnO, MgO, SiO2, TiO2, MnCO3, SrCO3, CaCO3, BaCO3, Al2O3, ZrO2, and BO3. The insulator layer 20 may include a single ceramic material or may include two or more ceramic materials. The insulator layer 20 may include glass. The insulator layer 20 may include copper oxide (CuO or Cu2O) to enable low-temperature sintering.

[0017] The external electrodes 3 and 4 are arranged on the element body 2. The external electrodes 3 and 4 are arranged on the surface of the element body 2. The external electrodes 3 and 4 are arranged on the element body 2 so as to face each other in the first direction D1. The external electrodes 3 and 4 are arranged at both ends of the element body 2 in the first direction D1. The external electrode 4 is spaced apart from the external electrode 3. That is, the external electrodes 3 and 4 are spaced apart from each other. In this embodiment, the external electrodes 3 and 4 are spaced apart from each other in the first direction D1. That is, in this embodiment, the direction in which the external electrodes 3 and 4 are spaced apart from each other includes the first direction D1. For example, if the external electrode 3 includes a first external electrode, the external electrode 4 includes a second external electrode.

[0018] The external electrode 3 is disposed on the end face 2a. The external electrode 3 is connected to the internal electrode 5. The external electrode 3 is physically and electrically connected to the internal electrode 5. The external electrode 3 covers the end face 2a. The external electrode 3 also covers a portion of each of the four side faces 2c, 2d, 2e, and 2f. Each portion of the four side faces 2c, 2d, 2e, and 2f that is covered by the external electrode 3 is located closer to the end face 2a on the corresponding side face 2c, 2d, 2e, and 2f. The external electrode 3 is disposed over the entire end face 2a and on the ends of the side faces 2c, 2d, 2e, and 2f that are closer to the end face 2a.

[0019] The external electrode 4 is disposed on the end face 2b. The external electrode 4 is connected to the internal electrode 6. The external electrode 4 is physically and electrically connected to the internal electrode 6. The external electrode 4 covers the end face 2b. The external electrode 4 also covers a portion of each of the four side faces 2c, 2d, 2e, and 2f. Each portion of the four side faces 2c, 2d, 2e, and 2f that is covered by the external electrode 4 is located closer to the end face 2b on the corresponding side face 2c, 2d, 2e, and 2f. The external electrode 4 is disposed over the entire end face 2b and on the ends of the side faces 2c, 2d, 2e, and 2f that are closer to the end face 2b.

[0020] The internal electrodes 5 and 6 are arranged within the element body 2. The internal electrode 6 faces the internal electrode 5 within the element body 2. That is, the internal electrodes 5 and 6 face each other within the element body 2. In this embodiment, the internal electrodes 5 and 6 face each other in the second direction D2. That is, in this embodiment, the direction in which the internal electrodes 5 and 6 face each other includes the second direction D2. Each of the internal electrodes 5 and 6 extends in the first direction D1. The internal electrode 5 is arranged closer to the side surface 2e. The internal electrode 6 is arranged closer to the side surface 2f.

[0021] The internal electrodes 5 and 6 are arranged, for example, in the same layer. In this embodiment, the internal electrodes 5 and 6 are arranged at the same height position, i.e., the same stacking position, in the third direction D3. As shown in FIG. 2, the internal electrodes 5 and 6 are arranged on the same insulator layer 20. The internal electrodes 5 and 6 are arranged approximately in the center in the third direction D3, i.e., the stacking direction of the insulator layers 20.

[0022] As shown in FIG. 3, the internal electrode 5 includes a pair of edges 5a and 5b, a pair of faces 5c and 5d, and a pair of ends 5e and 5f. The pair of edges 5a and 5b face each other. In this embodiment, the pair of edges 5a and 5b face each other in the second direction D2. The edge 5a faces the internal electrode 6. The edge 5a faces the internal electrode 6 in the second direction D2. The edge 5b is farther from the internal electrode 6 than the edge 5a. Each of the edges 5a and 5b may form a surface. Each of the edges 5a and 5b is adjacent to the surface 5c and the surface 5d, respectively. The pair of surfaces 5c and 5d face each other. In this embodiment, the pair of surfaces 5c and 5d face each other in the third direction D3. The internal electrode 5 is spaced apart from the end surface 2b and the side surfaces 2c, 2d, 2e, and 2f. For example, if edge 5 a comprises a first edge of internal electrode 5 , edge 5 b comprises a second edge of internal electrode 5 .

[0023] The end 5e is exposed on the surface of the element body 2. The end 5e is exposed at the end face 2a. The end 5e is connected to the external electrode 3. In this embodiment, the end 5e is directly connected to the external electrode 3. The end 5e includes a connection end connected to the external electrode 3. The end 5e includes a tip face.

[0024] The end 5f is located within the element body 2. The end 5f is away from the surface of the element body 2. The end 5f is not exposed on the surface of the element body 2. The end 5f is spaced apart from each end face 2a, 2b. In this embodiment, the end 5f includes not only the tip of the internal electrode 5 but also a region extending from the tip of the internal electrode 5 to a predetermined length. Therefore, the end 5f has the predetermined length in the first direction D1. When viewed from the third direction D3, the end 5f is spaced apart from the external electrode 4 and does not overlap with the external electrode 4. For example, if the end 5e includes the first end, the end 5f includes the second end.

[0025] The internal electrode 6 includes a pair of edges 6a, 6b, a pair of surfaces 6c, 6d, and a pair of ends 6e, 6f. The pair of edges 6a, 6b face each other. In this embodiment, the pair of edges 6a, 6b face each other in the second direction D2. The edge 6a faces the internal electrode 5. The edge 6a faces the internal electrode 5 in the second direction D2. In this embodiment, the edge 6a faces the edge 5a in the second direction D2. That is, in this embodiment, the edges 5a, 6a face each other in the second direction D2. The edge 6b is farther from the internal electrode 5 than the edge 6a. Each of the edges 6a, 6b may form a surface. Each of the edges 6a, 6b is adjacent to the surface 6c and the surface 6d, respectively. The pair of surfaces 6c, 6d face each other. In this embodiment, the pair of surfaces 6c, 6d face each other in the third direction D3. The internal electrode 6 is spaced apart from the end face 2a and the side faces 2c, 2d, 2e, and 2f. For example, if the edge 6a comprises a first edge of the internal electrode 6, the edge 6b comprises a second edge of the internal electrode 6.

[0026] The end 6e is exposed on the surface of the element body 2. The end 6e is exposed at the end face 2b. The end 6e is connected to the external electrode 4. In this embodiment, the end 6e is directly connected to the external electrode 4. The end 6e includes a connection end connected to the external electrode 4. The end 6e includes a tip face.

[0027] The end 6f is located within the element body 2. The end 6f is away from the surface of the element body 2. The end 6f is not exposed on the surface of the element body 2. The end 6f is spaced apart from each end face 2a, 2b. In this embodiment, the end 6f includes not only the tip of the internal electrode 6 but also a region extending from the tip of the internal electrode 6 to a predetermined length. Therefore, the end 6f has the predetermined length in the first direction D1. When viewed from the third direction D3, the end 6f is spaced apart from the external electrode 3 and does not overlap with the external electrode 3. For example, if the end 6e includes the third end, the end 6f includes the fourth end.

[0028] The external electrodes 3, 4 and the internal electrodes 5, 6 contain a conductive material. The conductive material may include, for example, Ag, Pd, Au, Pt, Cu, Ni, Al, Mo, or W. The conductive material may include, for example, an Ag-Pd alloy, an Ag-Cu alloy, an Ag-Au alloy, or an Ag-Pt alloy. The external electrodes 3, 4 and the internal electrodes 5, 6 may contain the same conductive material. The external electrodes 3, 4 and the internal electrodes 5, 6 may also contain different conductive materials.

[0029] The external electrodes 3, 4 are formed, for example, by baking a conductive paste applied to the outer surface of the element body 2. The conductive paste for forming the external electrodes 3, 4 contains the above-mentioned conductive material. The internal electrodes 5, 6 are formed, for example, by firing a conductive paste applied to an insulator green sheet together with the insulator green sheet. The conductive paste is applied to the insulator green sheet by, for example, printing. The conductive paste for forming the internal electrodes 5, 6 also contains the above-mentioned conductive material.

[0030] As shown in FIGS. 2 to 4, the discharge auxiliary part 7 is disposed within the element body 2. The discharge auxiliary part 7 is disposed within the element body 2 so as to contact the internal electrodes 5 and 6. The discharge auxiliary part 7 is spaced apart from the surface of the element body 2. The discharge auxiliary part 7 is not exposed from the element body 2. The discharge auxiliary part 7 includes a pair of opposing edges 7a, 7b and a pair of opposing edges 7c, 7d. The pair of edges 7a, 7b face each other in the first direction D1, and the pair of edges 7c, 7d face each other in the second direction D2. In this embodiment, the edge 7a is located closer to the end face 2a, and the edge 7b is located closer to the end face 2b. The edge 7c is located closer to the side face 2f, and the edge 7d is located closer to the side face 2e. When viewed from the third direction D3, the discharge auxiliary part 7 has a rectangular shape defined by the four edges 7a, 7b, 7c, and 7d. The discharge auxiliary part 7 may have a rectangular shape with rounded corners or a rectangular shape with rounded corners. The discharge auxiliary part 7 is spaced apart from the outer surface of the element body 2.

[0031] The discharge auxiliary part 7 further includes a pair of surfaces 7e, 7f facing each other. The pair of surfaces 7e, 7f face each other in the third direction D3. The surface 7e contacts the internal electrodes 5, 6. The surface 7e contacts the surface 5d of the internal electrode 5 and the surface 6d of the internal electrode 6. The internal electrodes 5, 6 are disposed on the surface 7e. The surface 7e includes an area covered by the internal electrodes 5, 6 and an area exposed from the internal electrodes 5, 6. The surface 7f contacts the element body 2. The entire surface 7f is covered by the element body 2. The discharge auxiliary part 7 contacts the internal electrodes 5, 6 and connects the internal electrodes 5, 6 to each other. The internal electrodes 5 and 6 are connected to each other via the discharge auxiliary part 7. The discharge auxiliary part 7, together with the internal electrodes 5, 6, constitutes a transient voltage suppressor. The transient voltage suppressor has transient voltage absorption capabilities.

[0032] The discharge auxiliary part 7 includes an insulator and metal particles. The insulator includes, for example, a ceramic material. The ceramic material is selected from the group consisting of, for example, Fe2O3, NiO, CuO, ZnO, MgO, SiO2, TiO2, MnCO3, SrCO3, CaCO3, BaCO3, Al2O3, ZrO2, and B2O3. The discharge auxiliary part 7 may include only one ceramic material selected from this group, or may include two or more ceramic materials selected from this group. The metal particles include, for example, Ag, Pd, Au, Pt, Ag-Pd alloy, Ag-Cu alloy, Ag-Au alloy, or Ag-Pt alloy. The discharge auxiliary part 7 may include semiconductor particles. The semiconductor particles include, for example, RuO2. The discharge auxiliary part 7 may include glass.

[0033] The discharge auxiliary portion 7 is formed, for example, by applying a slurry to an insulator green sheet and firing the slurry together with the insulator green sheet. The slurry contains the ceramic material and metal particles. The slurry is applied to the insulator green sheet by, for example, printing.

[0034] 3 and 4, a cavity S is formed inside the element body 2. The cavity S is spaced apart from the outer surface of the element body 2. The surfaces defining the cavity S include the inner wall of the element body 2, the edges 5a, 5b and face 5c of the internal electrode 5, and the edges 6a, 6b and face 6c of the internal electrode 6. The surfaces defining the cavity S also include the areas of the discharge auxiliary part 7 that are exposed from the internal electrodes 5, 6. The discharge auxiliary part 7 includes an area exposed to the cavity S.

[0035] The cavity S is formed, for example, by firing an organic lacquer applied to the insulator green sheet together with the insulator green sheet. The cavity S is formed by burning off the organic lacquer. The organic lacquer contains an organic solvent and an organic binder. The organic lacquer is applied to the insulator green sheet by, for example, printing.

[0036] As shown in FIG. 3 , the end 5f of the internal electrode 5 and the end 6f of the internal electrode 6 are located between a pair of edges 7a and 7b of the discharge auxiliary portion 7 in the first direction D1. In this embodiment, the tips of the ends 5f and 6f are located between the pair of edges 7a and 7b in the first direction D1. The ends 5f and 6f are located inside the discharge auxiliary portion 7 when viewed from the third direction D3. The ends 5f and 6f do not have to be located between the pair of edges 7a and 7b in the first direction D1. The end 5f may be located between the edge 7b and the end face 2b in the first direction D1. The end 6f may be located between the edge 7a and the end face 2a in the first direction D1. The pair of edges 7a and 7b may be located between the tips of the ends 5f and 6f in the first direction D1. The ends 5f and 6f may be located outside the discharge auxiliary portion 7 when viewed from the third direction D3. The tip of the end 5f may overlap the edge 7b when viewed from the third direction D3, and the tip of the end 6f may overlap the edge 7a when viewed from the third direction D3.

[0037] The edge 5b of the internal electrode 5 and the edge 6b of the internal electrode 6 are located, for example, between a pair of edges 7c and 7d in the second direction D2. The edges 5b and 6b do not have to be located between the pair of edges 7c and 7d in the second direction D2. The edge 5b may be located between the edge 7d and the side surface 2e in the second direction D2. The edge 6b may be located between the edge 7c and the side surface 2f in the second direction D2. The pair of edges 7c and 7d may be located between the edge 5b and the edge 6b in the second direction D2. The edge 7c may be located, for example, between the edge 6a and the edge 6b in the second direction D2. The edge 7d may be located, for example, between the edge 5a and the edge 5b in the second direction D2. The edge 5b may overlap the edge 7d when viewed in the third direction D3. The edge 6b may overlap the edge 7c when viewed from the third direction D3.

[0038] The tip of the end 5f overlaps, for example, with the end S1, which is one end of the cavity S in the first direction D1 and is closer to the end face 2b, as viewed from the third direction D3. The tip of the end 6f overlaps, for example, with the end S2, which is the other end of the cavity S in the first direction D1 and is closer to the end face 2a, as viewed from the third direction D3. The tip of the end 5f does not have to overlap with the end S1 when viewed from the third direction D3. The tip of the end 5f may be located inside the cavity S or outside the cavity S when viewed from the third direction D3. The tip of the end 5f may be located between the end S1 and the end S2, or between the end S1 and the end face 2b in the second direction D2.

[0039] The tip of the end 6f does not have to overlap with the end S2 when viewed from the third direction D3. The tip of the end 6f may be located inside the cavity S or outside the cavity S when viewed from the third direction D3. The tip of the end 6f may be located between the end S1 and the end S2, or between the end S2 and the end face 2a in the second direction D2.

[0040] For example, the edges 5b and 6b are located in the second direction D2 between an edge S3, which is one end of the cavity S in the second direction D2 and is closer to the side surface 2e, and an edge S4, which is the other end of the cavity S in the second direction D2 and is closer to the side surface 2f. The edges 5b and 6b do not have to be located between the edges S3 and S4 in the second direction D2. The edge 5b may be located between the edge S3 and the side surface 2e in the second direction D2. The edge 6b may be located between the edge S4 and the side surface 2f in the second direction D2. The edges S3 and S4 may be located between the edges 5b and 6b in the second direction D2. The edge 5b may overlap the edge S3 when viewed from the third direction D3. The edge 6b may overlap the edge S4 when viewed from the third direction D3.

[0041] In this embodiment, the ends S1 and S2 are located, for example, between the pair of edges 7a and 7b in the first direction D1. The ends S1 and S2 are located inside the discharge auxiliary part 7 when viewed from the third direction D3. The ends S1 and S2 do not have to be located between the pair of edges 7a and 7b in the first direction D1. The end S1 may be located between the edge 7b and the end face 2b in the first direction D1. The end S2 may be located between the edge 7a and the end face 2a in the first direction D1. The ends S1 and S2 may be located outside the discharge auxiliary part 7 when viewed from the third direction D3. The end S1 may overlap the edge 7a when viewed from the third direction D3. The end S2 may overlap the edge 7b when viewed from the third direction D3.

[0042] In this embodiment, the end S3 overlaps with the edge 7d when viewed from the third direction D3, for example, and the end S4 overlaps with the edge 7c when viewed from the third direction D3, for example. End S3 does not have to overlap with edge 7d when viewed from the third direction D3. End S3 may be located inside or outside discharge auxiliary part 7 when viewed from the third direction D3. End S3 may be located between the pair of edges 7c, 7d in the second direction D2, or between edge 7d and side surface 2e. End S4 does not have to overlap with edge 7c when viewed from third direction D3. End S4 may be located inside or outside discharge auxiliary part 7 when viewed from third direction D3. End S4 may be located between the pair of edges 7c, 7d, or between edge 7c and side surface 2f in second direction D2.

[0043] The length d1 of the cavity S in the first direction D1 and the length d2 in the second direction D2 are equal to or greater than the shortest distance d3 between the internal electrodes 5 and 6 at the positions where the internal electrodes 5 and 6 face each other. The length d1 is determined, for example, by the distance between the ends S1 and S2 in the first direction D1. The length d2 is determined, for example, by the distance between the ends S3 and S4 in the second direction D2. The shortest distance d3 is determined, for example, by the shortest distance between the edges 5a and 6a at the positions where the internal electrodes 5 and 6 face each other.

[0044] The length d1 may be, for example, equal to or less than the length of the discharge auxiliary part 7 in the first direction D1, or may be greater than the length of the discharge auxiliary part 7 in the first direction D1. The length d2 may be, for example, equal to or less than the length of the discharge auxiliary part 7 in the second direction D2, or may be greater than the length of the discharge auxiliary part 7 in the second direction D2. The length of the discharge auxiliary part 7 in the first direction D1 is determined, for example, by the distance between the edge 7a and the edge 7b in the first direction D1. The length of the discharge auxiliary part 7 in the second direction D2 is determined, for example, by the distance between the edge 7c and the edge 7d in the second direction D2.

[0045] As described above, in this embodiment, the end 5f has a predetermined length in the first direction D1. As shown in FIG. 5, in this embodiment, both ends of the end 5f in the first direction D1 are defined by points P1, P2, and P3. Point P1 is, for example, one end of the end 5f in the first direction D1, and is the tip of the end 5f. Points P2 and P3 are, for example, the other ends of the end 5f in the first direction D1, and are located closer to the end 5e than point P1. In this embodiment, points P2 and P3 are located at the same position in the first direction D1, and point P2 is located closer to the internal electrode 6 than point P3.

[0046] The end 5f of the internal electrode 5 includes a pair of corner portions 51, 52 adjacent to each other in the second direction D2. In this embodiment, the corner portion 51 is formed at the end 5f by the surface 5c and the edge 5a. The corner portion 51 includes an edge 51a facing the internal electrode 6. The edge 51a is included in, for example, the edge 5a. That is, the edge 5a includes, for example, the edge 51a. In this embodiment, the portion of the edge 5a that is located between the point P1 and the point P2 constitutes the edge 51a.

[0047] Corner portion 52 is formed at end 5f by surface 5c and edge 5b. Corner portion 52 includes edge 52a. Edge 52a is included in edge 5b, for example. That is, edge 5b includes edge 52a, for example. In this embodiment, the portion of edge 5b that is located between points P1 and P3 constitutes edge 52a.

[0048] The edge 51a is curved in a plan view of the internal electrode 5. That is, in the internal electrode 5, the corners of the corner portions 51 are rounded at the end 5f. The plan view of the internal electrode 5 includes, for example, viewing the surface 5c of the internal electrode 5 from the third direction D3. In this embodiment, the edge 51a is curved between points P1 and P2 in a plan view of the internal electrode 5. The edge 51a is curved such that, for example, the distance between the edge 51a and the internal electrode 6 in the second direction D2 increases toward point P1. That is, at the end 5f, the distance between the internal electrode 5 and the internal electrode 6 in the second direction D2 increases toward the tip of the end 5f.

[0049] In this embodiment, the radius of curvature R1 of the edge 51a is constant, for example, between points P1 and P2. In this embodiment, the radius of curvature R1 is the same as the width of the internal electrode 5. That is, in this embodiment, the edge 51a has a radius of curvature R1 that is the same as the width of the internal electrode 5. The width of the internal electrode 5 is determined, for example, by the length of the internal electrode 5 in the second direction D2. The length of the internal electrode 5 in the second direction D2 includes, for example, the distance between the edge 5a and the edge 5b in the second direction D2 at a position closer to the end 5e than points P2 and P3. The radius of curvature R1 does not have to be constant, for example, between points P1 and P2.

[0050] In the present embodiment, the edge 52a is not curved in a plan view of the internal electrode 5. The edge 52a extends, for example, along the first direction D1 in a plan view of the internal electrode 5. That is, in the internal electrode 5, the corner of the corner portion 52 at the end 5f is not rounded. For example, when the corner portion 51 includes a first corner portion of the internal electrode 5 , the corner portion 52 includes a second corner portion of the internal electrode 5 .

[0051] As described above, in this embodiment, the end 6f has a predetermined length in the first direction D1. In this embodiment, both ends of the end 6f in the first direction D1 are defined by points P4, P5, and P6. Point P4 is, for example, one end of the end 6f in the first direction D1 and is the tip of the end 6f. Points P5 and P6 are, for example, the other ends of the end 6f in the first direction D1 and are located closer to the end 6f than point P4. In this embodiment, points P5 and P6 are located at the same position in the first direction D1, and point P5 is located closer to the internal electrode 5 than point P6.

[0052] The end 6f of the internal electrode 6 includes a pair of corner portions 61, 62 adjacent to each other in the second direction D2. In this embodiment, the corner portion 61 is formed by the surface 6c and the edge 6a at the end 6f. The corner portion 61 includes an edge 61a facing the internal electrode 5. The edge 61a is included in, for example, the edge 6a. That is, the edge 6a includes, for example, the edge 61a. In this embodiment, the portion of the edge 6a that is located between the point P4 and the point P5 forms the edge 61a.

[0053] The corner portion 62 is formed at the end 6f by the surface 6c and the edge 6b. The corner portion 62 includes an edge 62a. The edge 62a is included in the edge 6b, for example. That is, the edge 6b includes the edge 62a, for example. In this embodiment, the portion of the edge 6b that is located between the point P4 and the point P6 constitutes the edge 62a.

[0054] The edge 61a is curved in a plan view of the internal electrode 6. That is, in the internal electrode 6, the corners of the corner portions 61 are rounded at the end 6f. The plan view of the internal electrode 6 includes, for example, viewing the surface 6c of the internal electrode 6 from the third direction D3. In this embodiment, the edge 61a is curved between points P4 and P5 in a plan view of the internal electrode 6. The edge 61a is curved such that, for example, the distance between the edge 61a and the internal electrode 5 in the second direction D2 increases toward point P4. That is, at the end 6f, the distance between the internal electrode 5 and the internal electrode 6 in the second direction D2 increases toward the tip of the end 6f.

[0055] In this embodiment, the radius of curvature R2 of the edge 61a is constant, for example, between points P4 and P5. In this embodiment, the radius of curvature R2 is the same as the width of the internal electrode 6. That is, in this embodiment, the edge 61a has a radius of curvature R2 that is the same as the width of the internal electrode 6. The width of the internal electrode 6 is determined, for example, by the length of the internal electrode 6 in the second direction D2. The length of the internal electrode 6 in the second direction D2 includes, for example, the distance between the edge 6a and the edge 6b in the second direction D2 at a position closer to the end 6e than points P5 and P6. In this embodiment, the radius of curvature R1 and the radius of curvature R2 are the same. The radius of curvature R1 and the radius of curvature R2 may be different from each other. The radius of curvature R2 may not be constant, for example, between points P4 and P5.

[0056] In this embodiment, the edge 62a is not curved in a plan view of the internal electrode 6. The edge 62a extends, for example, along the first direction D1 in a plan view of the internal electrode 6. That is, in the internal electrode 6, the corner of the corner portion 62 at the end 6f is not rounded. For example, when the corner portion 61 includes the third corner portion of the internal electrode 6, the corner portion 62 includes the fourth corner portion of the internal electrode 6.

[0057] As described above, in the transient voltage protection device 1, the edge 51a included in the corner portion 51 is curved in a plan view of the internal electrode 5. Therefore, a location where an electric field is likely to concentrate is unlikely to occur at the end 5f, and discharge is unlikely to concentrate locally. Similarly, in the transient voltage protection device 1, the edge 61a included in the corner portion 61 is curved in a plan view of the internal electrode 6. Therefore, a location where an electric field is likely to concentrate is unlikely to occur at the end 6f, and discharge is unlikely to concentrate locally. As a result, the transient voltage protection device 1 suppresses deterioration of the transient voltage protection characteristics.

[0058] As described above, the internal electrodes 5, 6 are formed, for example, by firing a conductive paste applied to an insulator green sheet together with the insulator green sheet. A slurry for forming the discharge auxiliary portion 7 is applied to the insulator green sheet on which the conductive paste is applied. That is, when forming the internal electrodes 5, 6, the conductive paste for forming the internal electrodes 5, 6 is applied to the insulator green sheet on top of the slurry for forming the discharge auxiliary portion 7. When the conductive paste is applied to the insulator green sheet so that the ends 5f and 6f are positioned outside the pair of edges 7a, 7b in the first direction D1, the conductive paste may spread outward from the applied locations at the positions that will become the edges 7a, 7b.

[0059] If the insulator green sheet is fired with the conductive paste spreading outward from the applied area, the internal electrodes 5 and 6 may be electrically connected outside the discharge auxiliary section 7, which could result in a short circuit. In contrast, if the conductive paste is applied to the insulator green sheet so that the ends 5f and 6f are located between the pair of edges 7a and 7b in the first direction D1, the internal electrodes 5 and 6 are unlikely to be electrically connected even if the conductive paste spreads outward from the applied area. In other words, the transient voltage protection device 1 in which the ends 5f and 6f are located between the pair of edges 7a and 7b in the first direction D1 suppresses the occurrence of a short circuit between the internal electrodes 5 and 6.

[0060] In the transient voltage protection device 1, repeated discharges between the internal electrodes 5 and 6 may cause the length of the discharge auxiliary portion 7 in the second direction D2 to decrease. If the length of the discharge auxiliary portion 7 in the second direction D2 decreases, the pair of edges 7c and 7d may be positioned between the edges 5a and 6a in the second direction D2, potentially causing the discharge auxiliary portion 7 to lose contact with the internal electrodes 5 and 6. If the discharge auxiliary portion 7 does not contact the internal electrodes 5 and 6, the discharge start voltage may increase, potentially degrading the transient voltage protection characteristics. In contrast, in the transient voltage protection device 1 in which the edges 5b and 6b are positioned between the pair of edges 7c and 7d in the second direction D2, the discharge auxiliary portion 7 is more likely to come into contact with the internal electrodes 5 and 6 even if the length of the discharge auxiliary portion 7 in the second direction D2 decreases. As a result, the transient voltage protection device 1 can further suppress degradation of the transient voltage protection characteristics.

[0061] Next, a modified example of the transient voltage protection device 1 according to this embodiment will be described with reference to Fig. 6. Fig. 6 is a plan view showing the configuration of the internal electrodes. This modified example differs from the above-described embodiment in terms of the configurations of the internal electrodes 5 and 6. The following mainly describes the differences between this modified example and the above-described embodiment.

[0062] 6, in this modification, the edge 51a is curved between points P2 and P7 in a plan view of the internal electrode 5. Point P7 is located at the same position as point P1 in the first direction D1 and between points P2 and P3 in the second direction D2. In this modification, the edge 51a is curved such that, for example, the distance between the edge 51a and the internal electrode 6 in the second direction D2 increases with increasing distance from point P7. As described above, the position of point P7 in the first direction D1 is the same as the position of point P1 in the first direction D1. Therefore, in this modification, the distance between the internal electrode 5 and the internal electrode 6 in the second direction D2 at the end 5f also increases with increasing distance from the tip of the end 5f.

[0063] In this modified example, the radius of curvature R1 is constant, for example, between points P2 and P7. In this modified example, the radius of curvature R1 is smaller than the width of the internal electrode 5. The edge 51a has a radius of curvature R1 whose length is smaller than the width of the internal electrode 5. The radius of curvature R1 may be, for example, greater than or equal to 1 / 4 and less than or equal to 1 / 2 of the width of the internal electrode 5. In this modified example, the radius of curvature R1 is 1 / 2 of the width of the internal electrode 5. The radius of curvature R1 does not have to be constant between points P2 and P7.

[0064] In this modification, the edge 61a is curved between points P5 and P8 in a plan view of the internal electrode 6. Point P8 is located at the same position as point P4 in the first direction D1 and between points P5 and P6 in the second direction D2. In this modification, the edge 61a is curved such that, for example, the distance between the edge 61a and the internal electrode 5 in the second direction D2 increases with increasing distance to point P8. As described above, the position of point P8 in the first direction D1 is the same as the position of point P4 in the first direction D1. Therefore, in this modification as well, at the end 6f, the distance between the internal electrode 5 and the internal electrode 6 in the second direction D2 increases with increasing distance to the tip of the end 6f.

[0065] In this modified example, the radius of curvature R2 is constant, for example, between points P5 and P8. In this modified example, the radius of curvature R2 is smaller than the width of the internal electrode 6. The edge 61a has a radius of curvature R2 whose length is smaller than the width of the internal electrode 6. The radius of curvature R2 may be, for example, greater than or equal to 1 / 4 and less than or equal to 1 / 2 of the width of the internal electrode 6. In this modified example, the radius of curvature R2 is 1 / 2 of the width of the internal electrode 6. The radius of curvature R2 does not have to be constant between points P5 and P8.

[0066] Next, another modified example of the transient voltage protection device 1 according to this embodiment will be described with reference to Fig. 7. Fig. 7 is a plan view showing the configuration of the internal electrodes. This modified example differs from the modified example described above in terms of the configurations of the internal electrodes 5 and 6. The following mainly describes the differences between this modified example and the modified example described above.

[0067] As shown in FIG. 7 , in this modification, the edge 52a is curved in a plan view of the internal electrode 5. That is, in this modification, the corner portion 52 includes an edge 52a that is curved in a plan view of the internal electrode 5. For example, the edge 52a is curved between points P9 and P1 in a plan view of the internal electrode 5. Point P9 is located between points P1 and P3 in the first direction D1 and is located at the same position as point P3 in the second direction D2. In this modification, the edge 52a is curved such that the distance between the edge 52a and the side surface 2e in the second direction D2 increases toward point P1. The edge 52a extends along the first direction D1 between points P3 and P9 in a plan view of the internal electrode 5. That is, in this modification, the edge 52a includes a curved portion and a portion that extends along the first direction D1 in a plan view of the internal electrode 5.

[0068] In this modification, the radius of curvature R3 of the edge 52a is constant, for example, between points P1 and P9. As shown in FIG. 7, in this modification, the radius of curvature R3 is smaller than the radius of curvature R1. That is, the edge 51a has a radius of curvature R1 that is larger than the radius of curvature R3 of the edge 52a. The radius of curvature R3 may be, for example, greater than or equal to 1 / 6 and less than or equal to 1 / 2 of the radius of curvature R1. The radius of curvature R3 may also be the same as the radius of curvature R1.

[0069] In this modification, the edge 62a is curved in a plan view of the internal electrode 6. That is, in this modification, the corner portion 62 includes an edge 62a that is curved in a plan view of the internal electrode 6. For example, the edge 62a is curved between points P4 and P10 in a plan view of the internal electrode 6. Point P10 is located between points P4 and P6 in the first direction D1 and is located at the same position as point P6 in the second direction D2. In this modification, the edge 62a is curved such that the distance between the edge 62a and the side surface 2f in the second direction D2 increases toward point P4. The edge 62a extends along the first direction D1 between points P6 and P10 in a plan view of the internal electrode 6. That is, in this modification, the edge 62a includes a curved portion and a portion extending along the first direction D1 in a plan view of the internal electrode 6.

[0070] In this modification, the radius of curvature R4 of the edge 62a is constant, for example, between points P4 and P10. In this modification, the radius of curvature R4 is smaller than the radius of curvature R2. That is, the edge 61a has a radius of curvature R2 that is larger than the radius of curvature R4 of the edge 62a. The radius of curvature R4 may be, for example, greater than or equal to 1 / 6 and less than or equal to 1 / 2 of the radius of curvature R2. In this modification, the radius of curvature R4 is 1 / 2 of the radius of curvature R2. The radius of curvature R4 may be the same as the radius of curvature R2.

[0071] The above describes the embodiments and modifications of the present invention, but the present invention is not necessarily limited to the above-described embodiments and modifications, and various modifications are possible within the scope of the gist of the present invention.

[0072] In the above-described embodiment and each modified example, the edge 51 a of the corner portion 51 is curved in a plan view of the internal electrode 5, and the edge 61 a of the corner portion 61 is curved in a plan view of the internal electrode 6. However, the edges 51 a and 61 a of both the internal electrodes 5 and 6 do not have to be curved as described above. For example, in the transient voltage protection device 1, the edge 51 a may be curved in a plan view of the internal electrode 5, and the edge 61 a may not be curved in a plan view of the internal electrode 6. Alternatively, in the transient voltage protection device 1, the edge 61 a may be curved in a plan view of the internal electrode 6, and the edge 51 a may not be curved in a plan view of the internal electrode 5. In other words, one of the internal electrodes 5 and 6 may have a rectangular shape in a plan view of the internal electrode.

[0073] As can be understood from the above description of the embodiments, the present specification includes disclosure of the following aspects. (Appendix 1) The base body and a first external electrode disposed on a surface of the element body; a second external electrode disposed on the surface of the element body and spaced apart from the first external electrode; a first internal electrode disposed within the element body and connected to the first external electrode; a second internal electrode facing the first internal electrode within the element body and connected to the second external electrode, The first internal electrode is a first end exposed on the surface of the element body and connected to the first external electrode; a second end located within the element body and spaced from the surface of the element body; the second end includes a pair of corner portions adjacent to each other in a direction in which the first internal electrode and the second internal electrode face each other, the first corner portion including an edge facing the second internal electrode, and a second corner portion being farther from the second internal electrode than the first corner portion, A transient voltage protection device, wherein the edge included in the first corner portion is curved in a plan view of the first internal electrode. (Appendix 2) the second corner portion includes an edge of the first internal electrode that is curved in a plan view, 2. The transient voltage protection device of claim 1, wherein the edge included in the first corner portion has a radius of curvature that is greater than the radius of curvature of the edge included in the second corner portion. (Appendix 3) 3. The transient voltage protection device of claim 1, wherein the first internal electrode and the second internal electrode are located in the same layer. (Appendix 4) A transient voltage protection device according to any one of appendices 1 to 3, wherein the edge included in the first corner portion has a radius of curvature the same length as the width of the first internal electrode. (Appendix 5) a discharge auxiliary part disposed in the element body so as to be in contact with the first internal electrode and the second internal electrode, The second internal electrode is a third end exposed on the surface of the element body and connected to the second external electrode; a fourth end located within the element body and spaced from the surface of the element body; the discharge auxiliary portion includes a pair of edges facing each other in a direction in which the first external electrode and the second external electrode are spaced apart from each other, The transient voltage protection device according to any one of appendices 1 to 4, wherein the second end and the fourth end are located between the pair of edges in the direction in which the first external electrode and the second external electrode are spaced apart from each other. (Appendix 6) each of the first internal electrode and the second internal electrode includes a first edge and a second edge facing each other in the direction in which the first internal electrode and the second internal electrode face each other; the first end edges face each other in the direction in which the first internal electrode and the second internal electrode face each other, the second edge is farther from the corresponding one of the first internal electrode and the second internal electrode than the first edge; the discharge auxiliary portion includes another pair of edges facing each other in the direction in which the first internal electrode and the second internal electrode face each other, 6. The transient voltage protection device of claim 5, wherein each of the second edges is located between another pair of edges in the direction in which the first internal electrode and the second internal electrode face each other. (Appendix 7) A cavity is formed inside the element body, the first internal electrode and the second internal electrode face each other in the cavity, 7. The transient voltage protection device according to any one of appendices 1 to 6, wherein the length of the cavity in the direction in which the first internal electrode and the second internal electrode face each other and the length of the cavity in the direction in which the first external electrode and the second external electrode are separated from each other are equal to or greater than the shortest distance between the first internal electrode and the second internal electrode at the position where the first internal electrode and the second internal electrode face each other. (Appendix 8) The second internal electrode is a third end exposed on the surface of the element body and connected to the second external electrode; a fourth end located within the element body and spaced from the surface of the element body; the fourth end includes a pair of corner portions adjacent to each other in the direction in which the first internal electrode and the second internal electrode face each other, the fourth end including a third corner portion including an edge facing the first internal electrode, and a fourth corner portion farther from the first internal electrode than the third corner portion, The transient voltage protection device according to any one of appendices 1 to 7, wherein the edge included in the third corner portion is curved in a plan view of the second internal electrode. (Appendix 9) the fourth corner portion includes an edge of the second internal electrode that is curved in a plan view, 9. The transient voltage protection device of claim 8, wherein the edge included in the third corner portion has a radius of curvature that is greater than the radius of curvature of the edge included in the fourth corner portion. [Explanation of symbols]

[0074] 1...transient voltage protection device, 2...element body, 5, 6...internal electrodes, 5a, 5b, 6a, 6b...edges, 7...discharge auxiliary portions, 7a, 7b, 7c, 7d...edges, 51, 52, 61, 62...corner portions, 51a, 61a...edges, d1...length, d2...length, d3...shortest distance, R1, R2...radius of curvature, S...cavity.

Claims

1. The base body and a first external electrode disposed on a surface of the element body; a second external electrode disposed on the surface of the element body and spaced apart from the first external electrode; a first internal electrode disposed within the element body and connected to the first external electrode; a second internal electrode facing the first internal electrode within the element body and connected to the second external electrode, The first internal electrode is a first end exposed on the surface of the element body and connected to the first external electrode; a second end located within the element body and spaced from the surface of the element body; the second end includes a pair of corner portions adjacent to each other in a direction in which the first internal electrode and the second internal electrode face each other, the first corner portion including an edge facing the second internal electrode, and a second corner portion being farther from the second internal electrode than the first corner portion, A transient voltage protection device, wherein the edge included in the first corner portion is curved in a plan view of the first internal electrode.

2. the second corner portion includes an edge of the first internal electrode that is curved in a plan view, The transient voltage protection device of claim 1 , wherein the edge included in the first corner portion has a radius of curvature that is greater than the radius of curvature of the edge included in the second corner portion.

3. The transient voltage protection device according to claim 1 or 2, wherein the first internal electrode and the second internal electrode are located in the same layer.

4. The transient voltage protection device according to claim 1 or 2, wherein the edge included in the first corner portion has a radius of curvature the same length as the width of the first internal electrode.

5. a discharge auxiliary part disposed in the element body so as to be in contact with the first internal electrode and the second internal electrode, The second internal electrode is a third end exposed on the surface of the element body and connected to the second external electrode; a fourth end located within the element body and spaced from the surface of the element body; the discharge auxiliary portion includes a pair of edges facing each other in a direction in which the first external electrode and the second external electrode are spaced apart from each other, 3. The transient voltage protection device according to claim 1, wherein the second end and the fourth end are located between the pair of edges in the direction in which the first external electrode and the second external electrode are spaced apart from each other.

6. each of the first internal electrode and the second internal electrode includes a first edge and a second edge facing each other in the direction in which the first internal electrode and the second internal electrode face each other; the first end edges face each other in the direction in which the first internal electrode and the second internal electrode face each other, the second edge is farther from the corresponding one of the first internal electrode and the second internal electrode than the first edge; the discharge auxiliary portion includes another pair of edges facing each other in the direction in which the first internal electrode and the second internal electrode face each other, 6. The transient voltage protection device according to claim 5, wherein each of the second edges is located between the other pair of edges in the direction in which the first internal electrode and the second internal electrode face each other.

7. A cavity is formed inside the element body, the first internal electrode and the second internal electrode face each other in the cavity, 3. The transient voltage protection device according to claim 1, wherein a length of the cavity in the direction in which the first internal electrode and the second internal electrode face each other and a length of the cavity in the direction in which the first external electrode and the second external electrode are separated from each other are equal to or greater than a shortest distance between the first internal electrode and the second internal electrode at a position where the first internal electrode and the second internal electrode face each other.

8. The second internal electrode is a third end exposed on the surface of the element body and connected to the second external electrode; a fourth end located within the element body and spaced from the surface of the element body; the fourth end includes a pair of corner portions adjacent to each other in the direction in which the first internal electrode and the second internal electrode face each other, the fourth end including a third corner portion including an edge facing the first internal electrode, and a fourth corner portion farther from the first internal electrode than the third corner portion, The transient voltage protection device according to claim 1 , wherein the edge included in the third corner portion is curved in a plan view of the second internal electrode.

9. the fourth corner portion includes an edge of the second internal electrode that is curved in a plan view, The transient voltage protection device of claim 8 , wherein the edge included in the third corner portion has a radius of curvature that is greater than the radius of curvature of the edge included in the fourth corner portion.

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