Transient Voltage Protection Devices

Abstract

To provide a transient voltage protection device that can control a discharge part.SOLUTION: A transient voltage protection device 1 comprises: an element assembly 2 that has a cavity S formed therein; internal electrodes 5, 6 that extend along a first direction D1 and are provided in the element assembly 2 to face each other across the cavity S; external electrodes 3, 4 that are connected with the internal electrodes 5, 6; and a discharge auxiliary unit 7 that is provided in the element assembly 2 to be in contact with the internal electrodes 5. 6. The internal electrodes 5, 6 have a principal surface 5f and a principal surface 6f facing each other in a second direction D2 orthogonal to the first direction D1, and apical surfaces 5b, 6b connecting the principal surface 5f and principal surface 6f with each other, respectively. Principal surfaces are in contact with the discharge auxiliary unit 7. The principal surfaces 5f, 6f are in contact with the element assembly 2. The apical surfaces 5b, 6b are in contact with the element assembly 2. The element assembly 2 has a projection that enters the inside of the cavity S from between the principal surfaces 5f, 6f and is located between the apical surfaces 5b, 6b.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to transient voltage protection devices. [Background technology]

[0002] Patent Document 1 describes an ESD (Electro-Static Discharge) protection device that includes a magnetic substrate having a cavity formed therein, a pair of opposing electrodes arranged opposite each other within the cavity, a pair of external electrodes connected to the pair of opposing electrodes, and a discharge auxiliary electrode in contact with the pair of opposing electrodes. This ESD protection device can achieve high ESD resistance because discharge is easily generated in the cavity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2012 / 050073 Summary of the Invention [Problem to be solved by the invention]

[0004] The ESD protection device described in Patent Document 1 cannot control the location of discharge.

[0005] One aspect of the present disclosure provides a transient voltage protection device that can control the location of discharge. [Means for solving the problem]

[0006] A transient voltage protection device according to one aspect of the present disclosure comprises an element body having a cavity formed therein, a pair of internal electrodes extending along a first direction and provided within the element body so as to face each other across the cavity, a pair of external electrodes each connected to a corresponding one of the pair of internal electrodes, and a discharge auxiliary portion provided within the element body so as to be in contact with the pair of internal electrodes, wherein the pair of internal electrodes each have a first surface and a second surface facing each other in a second direction perpendicular to the first direction, and a third surface connecting the first surface and the second surface, wherein the first surface is in contact with the discharge auxiliary portion, the second surface is in contact with the element body, and the third surface is exposed to the cavity, and the element body has a protrusion extending into the cavity from between the pair of second surfaces and positioned between the pair of third surfaces.

[0007] In the transient voltage protection device, a pair of internal electrodes face each other across a cavity. Each of the pair of internal electrodes has a first surface in contact with the discharge auxiliary part, a second surface in contact with the element body, and a third surface connecting the first and second surfaces and exposed to the cavity. The element body has a protruding portion that extends into the cavity from between the pair of second surfaces and is located between the pair of third surfaces. This allows discharge to occur in a portion of the third surface closer to the first surface than in a portion of the third surface closer to the second surface.

[0008] The pair of internal electrodes may face each other in the first direction, in which case the element body can be made smaller in size in a direction perpendicular to the first direction.

[0009] The length of the pair of internal electrodes in the second direction may be longer than the length of the discharge auxiliary portion in the second direction. In this case, since the internal electrodes are thick, heat generation in the internal electrodes during discharge can be suppressed, thereby improving durability.

[0010] The protrusion may be provided so as to connect the pair of second surfaces to each other, in which case discharge at the portion of the third surface close to the second surface can be further suppressed.

[0011] The length of the pair of internal electrodes in the second direction may be longer than the length of the protruding portions in the second direction, in which case the protruding portions are prevented from interfering with discharge in the portion of the third surface closer to the first surface.

[0012] The distance between the pair of first surfaces may be shorter than the distance between the pair of second surfaces. In this case, the area of the discharge auxiliary portion exposed to the cavity is reduced, which can prevent the metal components contained in the discharge auxiliary portion from scattering. As a result, the possibility of a short circuit occurring can be reduced.

[0013] The pair of third surfaces may be inclined with respect to the second direction. In this case, the inclination of the third surfaces makes it possible to make the distance between the pair of first surfaces shorter than the distance between the pair of second surfaces. Therefore, the electric field is concentrated at the edge between the third surface and the first surface, thereby further controlling the discharge location. [Effects of the Invention]

[0014] According to one aspect of the present disclosure, the discharge location can be controlled. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view showing a transient voltage protection device according to an embodiment. [Figure 2] FIG. 2 is an exploded perspective view of the transient voltage protection device of FIG. [Figure 3] FIG. 3 is a perspective view of the transient voltage protection device of FIG. 1 as seen from the stacking direction. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Figure 5] FIG. 5 is a cross-sectional view of a transient voltage protection device according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, the embodiments 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.

[0017] The transient voltage protection device 1 according to this embodiment shown in FIGS. 1 to 4 is an electronic component mounted in an electronic device (not shown) to protect the electronic device from transient voltages such as ESD. The electronic device protected by the transient voltage protection device 1 includes, for example, a circuit board or an electronic component. 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 unit 7. The internal electrodes 5 and 6 are discharge electrodes configured to discharge. The internal electrodes 5 and 6, together with the discharge auxiliary unit 7, constitute a transient voltage suppressor. The transient voltage suppressor has transient voltage absorption capabilities.

[0018] 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 has, as its outer surfaces, a pair of opposing end faces 2a and 2b, a pair of opposing side faces 2c and 2d, and a pair of opposing side faces 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 opposing direction of the end faces 2a and 2b so as to connect the end face 2a and the end face 2b. One of the four side faces 2c, 2d, 2e, and 2f is defined as a mounting surface facing the electronic device to be protected.

[0019] In this embodiment, the opposing direction of the end faces 2a, 2b is defined as a first direction D1, the opposing direction of the side faces 2c, 2d as a second direction D2, and the opposing direction of the side faces 2e, 2f as a third direction D3. The first direction D1 is the length direction of the element body 2, the second direction D2 is the height direction of the element body 2, and the third direction D3 is the width direction of the element body 2. The length of the element body 2 (the length of the element body 2 in the first direction D1) is, for example, 0.4 mm or more and 2.0 mm or less. The height of the element body 2 (the length of the element body 2 in the second direction D2) is, for example, 0.2 mm or more and 1.2 mm or less. The width of the element body 2 (the length of the element body 2 in the third direction D3) is, for example, 0.2 mm or more and 1.2 mm or less. In this embodiment, the length of the element body 2 is 1.6 mm, the height of the element body 2 is 0.8 mm, and the width of the element body 2 is 0.8 mm.

[0020] A cavity S is formed inside the element body 2. The cavity S is formed away from the outer surface of the element body 2. The cavity S is formed in approximately the center of the element body 2 in each of the first direction D1, the second direction D2, and the third direction D3. The cavity S is located between the front end surface 5b of the internal electrode 5 and the front end surface 6b of the internal electrode 6 in the first direction D1. The length of the cavity S (the length of the cavity S in the first direction D1) is, for example, 0.01 mm or more and 0.2 mm or less. The height of the cavity S (the length of the cavity S in the second direction D2) is, for example, 5 μm or more and 50 μm or less. The width of the cavity S (the length of the cavity S in the third direction D3) is, for example, 0.05 mm or more and 0.6 mm or less.

[0021] 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.

[0022] As shown in Figure 2, the element body 2 has a plurality of insulator layers 10, a plurality of insulator layers 11, and a plurality of insulator layers 12 stacked in the second direction D2. A plurality of insulator layers 10 are arranged at both ends of the element body 2 in the stacking direction (second direction D2). The insulator layer 10 arranged at one end in the stacking direction has a side surface 2c. The insulator layer 10 arranged at the other end in the stacking direction has a side surface 2d.

[0023] In the center of the element body 2 in the stacking direction, multiple insulator layers 11 and multiple insulator layers 12 are arranged together with the internal electrodes 5 and 6 and the discharge auxiliary portions 7. The multiple insulator layers 11 are patterned to eliminate steps caused by stacking the discharge auxiliary portions 7. Each insulator layer 11 has a through-hole formed therein corresponding to the shape of the discharge auxiliary portion 7. The multiple insulator layers 11 are stacked in combination with the discharge auxiliary portions 7. The multiple insulator layers 12 are patterned to eliminate steps caused by stacking the internal electrodes 5 and 6. Each insulator layer 12 includes two patterns arranged on both sides of the internal electrodes 5 and 6 and the cavity S in the third direction D3. The multiple insulator layers 12 are stacked in combination with the internal electrodes 5 and 6 and the cavity S. The number of stacked insulator layers 11 is less than the number of stacked insulator layers 12. In this embodiment, the number is two, but it may be one, three, or more.

[0024] Each of the insulator layers 10, 11, and 12 is an electrically insulating insulator and is made of a sintered insulator green sheet. In the actual element body 2, the insulator layers 10, 11, and 12 are integrated to the extent that the boundaries between them are not visible. The thicknesses (lengths in the second direction D2) of the insulator layers 10, 11, and 12 are, for example, the same as each other.

[0025] The insulator layers 10, 11, and 12 are formed of, for example, the same material. Each of the insulator layers 10, 11, and 12 is made of a ceramic material such as Fe2O3, NiO, CuO, ZnO, MgO, SiO2, TiO2, MnCO3, SrCO3, CaCO3, BaCO3, Al2O3, ZrO2, or BO3. The insulator layer 10 may be made of a single ceramic material or a mixture of two or more ceramic materials. The insulator layers 10, 11, and 12 may contain glass. The insulator layers 10, 11, and 12 may contain copper oxide (CuO, Cu2O) to enable low-temperature sintering.

[0026] As shown in Figures 1 and 3, the external electrodes 3, 4 are provided on the outer surface of the element body 2. The external electrodes 3, 4 are arranged on the element body 2 so as to face each other in the first direction D1. The external electrodes 3, 4 are provided at both ends of the element body 2 in the first direction D1. The external electrodes 3, 4 are spaced apart from each other in the first direction D1. The external electrodes 3, 4 are not shown in Figure 2.

[0027] The external electrode 3 is provided on the end face 2a and connected to the internal electrode 5. The external electrode 3 is formed so as to cover the end face 2a and to have a portion thereof wrap around onto the side faces 2c, 2d, 2e, and 2f. The external electrode 3 is provided on the entire surface of the end face 2a and on the ends of the side faces 2c, 2d, 2e, and 2f on the end face 2a side.

[0028] The external electrode 4 is provided on the end face 2b and connected to the internal electrode 6. The external electrode 4 is formed so as to cover the end face 2b and to have a portion thereof wrap around onto the side faces 2c, 2d, 2e, and 2f. The external electrode 4 is provided on the entire surface of the end face 2b and on the ends of the side faces 2c, 2d, 2e, and 2f on the end face 2b side.

[0029] As shown in FIGS. 2 to 4, the internal electrodes 5, 6 are provided in the element body 2 at a distance from each other. The internal electrodes 5, 6 extend along the first direction D1. The internal electrodes 5, 6 face each other in the first direction D1 across the cavity S. The internal electrodes 5, 6 are arranged at the same height position (i.e., the same stacking position) in the second direction D2. The internal electrodes 5, 6 are arranged on the same insulator layer 11. The internal electrodes 5, 6 are provided approximately in the center of the stacking direction (second direction D2).

[0030] The internal electrodes 5 and 6 are provided approximately in the center of the element body 2 in the third direction D3. The internal electrodes 5 and 6 are arranged so that their centers in the third direction D3 coincide with each other. The center position of the internal electrode 5 in the third direction D3 is the intermediate position between the point on the internal electrode 5 that is closest to one side in the third direction D3 and the point on the internal electrode 5 that is closest to the other side in the third direction D3. The center position of the internal electrode 6 in the third direction D3 is the intermediate position between the point on the internal electrode 6 that is closest to one side in the third direction D3 and the point on the internal electrode 6 that is closest to the other side in the third direction D3. When viewed from the second direction D2, the center line of the internal electrode 5 in the third direction D3 and the center line of the internal electrode 6 in the third direction D3 coincide with each other. When viewed from the first direction D1, the internal electrodes 5 and 6 completely overlap each other.

[0031] The internal electrode 5 has a connection end face 5a, a tip face 5b, a side face 5c, a side face 5d, a main face 5e, and a main face 5f. The connection end face 5a is exposed at the end face 2a and is connected to the external electrode 3. The tip face 5b is located on the opposite side from the external electrode 3. The tip face 5b is spaced from the end face 2b. The connection end face 5a and the tip face 5b face each other in the first direction D1. The connection end face 5a and the tip face 5b each have a rectangular shape. The connection end face 5a and the tip face 5b connect the main face 5e and the main face 5f, respectively, and also connect the side face 5c and the side face 5d.

[0032] The tip surface 5b is inclined with respect to the first direction D1 and the second direction D2. The tip surface 5b is parallel to the third direction D3. The tip surface 5b is inclined from the main surface 5e toward the main surface 5f so as to approach the connecting end surface 5a.

[0033] Each side surface 5c, 5d extends in the first direction D1 so as to connect the connection end surface 5a and the tip surface 5b. The side surfaces 5c, 5d face each other in the third direction D3. The side surface 5c faces the side surface 2e in the third direction D3. The side surface 5d faces the side surface 2f in the third direction D3. When viewed from the second direction D2, the side surfaces 5c and 5d are parallel to each other. The side surfaces 5c, 5d have the same shape. The entire side surfaces 5c, 5d are in contact with the element body 2.

[0034] The main surfaces 5e, 5f extend in the first direction D1 so as to connect the connecting end surface 5a and the tip surface 5b. The main surfaces 5e, 5f face each other in the second direction D2. The main surface 5e faces the side surface 2c (see FIG. 1) in the second direction D2. The main surface 5e includes a portion in contact with the discharge auxiliary part 7. The main surface 5f faces the side surface 2d (see FIG. 1) in the second direction D2. The entire main surface 5f faces the element body 2. Each of the main surfaces 5e, 5f is adjacent to the connecting end surface 5a, the side surface 5c, and the side surface 5d, respectively. The length of the main surface 5e in the first direction D1 is longer than the length of the main surface 5f in the first direction D1.

[0035] The internal electrode 6 has a connection end face 6a, a tip face 6b, a side face 6c, a side face 6d, a main face 6e, and a main face 6f. The connection end face 6a is exposed at the end face 2b and is connected to the external electrode 4. The tip face 6b is located on the opposite side from the external electrode 4. The tip face 6b is spaced apart from the end face 2a. The connection end face 6a and the tip face 6b face each other in the first direction D1. The connection end face 6a and the tip face 6b each have a rectangular shape. The connection end face 6a and the tip face 6b connect the main face 6e and the main face 6f, and also connect the side face 6c and the side face 6d, respectively.

[0036] The tip surface 6b is inclined with respect to the first direction D1 and the second direction D2. The tip surface 6b is parallel to the third direction D3. The tip surface 6b is non-parallel to the tip surface 5b. The tip surface 6b is inclined from the main surface 6e toward the main surface 6f so as to approach the connecting end surface 6a.

[0037] Each side surface 6c, 6d extends in the first direction D1 so as to connect the connecting end surface 6a and the tip surface 6b. The side surfaces 6c, 6d face each other in the third direction D3. The side surface 6c faces the side surface 2e in the third direction D3. The side surface 6d faces the side surface 2f in the third direction D3. When viewed from the second direction D2, the side surfaces 6c and 6d are parallel to each other. The side surfaces 6c, 6d have the same shape. The entire side surfaces 6c, 6d are in contact with the element body 2.

[0038] The main surfaces 6e, 6f extend in the first direction D1 so as to connect the connecting end surface 6a and the tip surface 6b. The main surfaces 6e, 6f face each other in the second direction D2. The main surface 6e faces the side surface 2c (see FIG. 1) in the second direction D2. The main surface 6e includes a portion in contact with the discharge auxiliary part 7. The main surface 6f faces the side surface 2d (see FIG. 1) in the second direction D2. The entire main surface 6f faces the element body 2. Each of the main surfaces 6e, 6f is adjacent to the connecting end surface 6a, the side surface 6c, and the side surface 6d, respectively. The length of the main surface 6e in the first direction D1 is longer than the length of the main surface 6f in the first direction D1.

[0039] The internal electrodes 5, 6 have, for example, the same shape as each other. The length (maximum length) L1 in the second direction of the internal electrodes 5, 6 is 1 / 100 to 1 / 10 of the length in the second direction D2 of the element body 2. The length L1 is, for example, 5 μm to 50 μm. The length in the first direction D1 of the principal surfaces 5e, 6e is, for example, 0.2 mm to 1 mm. The length in the first direction D1 of the principal surfaces 5f, 6f is, for example, 0.2 mm to 1 mm. The length in the third direction D3 of the internal electrodes 5, 6 is, for example, 0.05 mm to 0.5 mm.

[0040] The distance d1 in the first direction D1 between the principal surfaces 5e and 6e is shorter than the distance d2 in the first direction D1 between the principal surfaces 5f and 6f. The distance d1 is, for example, 0.01 mm or more and 0.1 mm or less. The distance d2 is, for example, 0.01 mm or more and 0.2 mm or less. The tip surfaces 5b and 6b face each other in the first direction D1 via a cavity S. The tip surfaces 5b and 6b are inclined with respect to the second direction D2 so that the distance d between the tip surfaces 5b and 6b in the first direction D1 increases from the principal surfaces 5e and 6e toward the principal surfaces 5f and 6f. The distance d varies between d1 and d2. The tip surfaces 5b and 6b are inclined with respect to the second direction D2 so that the distance d increases with increasing distance from the discharge auxiliary portion 7 in the second direction D2. The length of the cavity S in the first direction D1 is equal to the distance d, and increases with increasing distance from the discharge auxiliary part 7 in the second direction D2.

[0041] The external electrodes 3, 4 and the internal electrodes 5, 6 are made of a conductive material containing, for example, Ag, Pd, Au, Pt, Cu, Ni, Al, Mo, or W. The external electrodes 3, 4 and the internal electrodes 5, 6 may be made of, 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 be made of the same material or different materials.

[0042] The external electrodes 3, 4 are formed, for example, by applying a conductive paste containing the above-mentioned conductive material to the outer surface of the element body 2 and then baking the conductive paste. The external electrodes 3, 4 may have a plating layer. The internal electrodes 5, 6 are formed, for example, by applying a conductive paste containing the above-mentioned conductive material to an insulator green sheet by printing and then baking the conductive paste together with the insulator green sheet.

[0043] The discharge auxiliary portion 7 is provided within the element body 2 so as to contact the main surfaces 5e, 6e of the internal electrodes 5, 6. The discharge auxiliary portion 7 is provided away from the outer surface of the element body 2. The discharge auxiliary portion 7 connects the internal electrodes 5, 6 to each other. The discharge auxiliary portion 7 is exposed from the internal electrodes 5, 6. The discharge auxiliary portion 7 is exposed to the cavity S.

[0044] As shown in FIG. 3, the discharge auxiliary portion 7 has a rectangular shape in a plan view (i.e., when viewed from the second direction D2). When viewed from the second direction D2, the discharge auxiliary portion 7 overlaps the cavity S and the front end faces 5b and 6b. When viewed from the second direction D2, the discharge auxiliary portion 7 overlaps the cavity S and the entire front end faces 5b and 6b. The length of the discharge auxiliary portion 7 in the first direction D1 is, for example, 0.01 mm or more and 0.2 mm or less. The length of the discharge auxiliary portion 7 in the third direction D3 is, for example, 0.05 mm or more and 0.6 mm or less. As shown in FIG. 4, the length L1 of the internal electrodes 5 and 6 in the second direction D2 is longer than the length L2 of the discharge auxiliary portion 7 in the second direction D2 (L1>L2). The length L2 of the discharge auxiliary portion 7 in the second direction D2 is, for example, 1 μm or more and 10 μm or less.

[0045] The discharge auxiliary part 7 includes an insulator and metal particles. The insulator is made of, for example, a ceramic material. Examples of ceramic materials include Fe2O3, NiO, CuO, ZnO, MgO, SiO2, TiO2, MnCO3, SrCO3, CaCO3, BaCO3, Al2O3, ZrO2, and B2O3. The discharge auxiliary part 7 may include only one of these ceramic materials or a mixture of two or more of them. The metal particles may be made of, 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 such as RuO2. The discharge auxiliary part 7 may include glass.

[0046] The discharge auxiliary portion 7 is formed, for example, by applying a slurry containing the above-mentioned ceramic material and metal particles onto an insulator green sheet by printing, and then firing the slurry together with the insulator green sheet.

[0047] The element body 2 has a protrusion 2g that extends into the cavity S between the main surfaces 5f and 6f and is located between the front end surfaces 5b and 6b. The protrusion 2g protrudes toward the discharge auxiliary part 7 beyond the main surfaces 5f, 6f in the second direction D2. The protrusion 2g faces the discharge auxiliary part 7 across the cavity S in the second direction D2. When viewed from the second direction D2, the protrusion 2g is provided so as to connect the main surfaces 5f and 6f to each other in the first direction D1. When viewed from the second direction D2, the protrusion 2g is provided over the entire region R (see FIG. 3 ) located between the main surfaces 5f and 6f in the first direction D1. The surface of the protrusion 2g is exposed to the cavity S. The surface of the protrusion 2g is curved toward the discharge auxiliary part 7.

[0048] The length L1 of the internal electrodes 5, 6 in the second direction D2 is longer than the length L3 of the protrusion 2g in the second direction D2 (L1>L3). When the main surfaces 5f, 6f are taken as reference planes, the length L3 is the maximum length by which the protrusion 2g protrudes in the second direction D2 from the reference plane.

[0049] As described above, in the transient voltage protection device 1, the pair of internal electrodes 5, 6 face each other across the cavity S. The pair of internal electrodes 5, 6 have main surfaces 5e, 6e in contact with the discharge auxiliary portion 7 and main surfaces 5f, 6f in contact with the element body 2. The element body 2 has a protrusion 2g that extends into the cavity S between the main surfaces 5f and 6f. The protrusion 2g increases the creepage distance at the portions of the tip surfaces 5b, 6b closer to the main surfaces 5f, 6f. Therefore, discharge can be generated at the portions of the tip surfaces 5b, 6b closer to the main surfaces 5e, 6e than at the portions of the tip surfaces 5b, 6b closer to the main surfaces 5f, 6f.

[0050] The pair of internal electrodes 5, 6 face each other in the extension direction (first direction D1). Therefore, the tip surfaces 5b, 6b located at the tips of the pair of internal electrodes 5, 6 in the extension direction face each other. Therefore, the element body 2 can be made smaller in the direction perpendicular to the extension direction than when the pair of internal electrodes 5, 6 face each other in a direction perpendicular to the extension direction (for example, the second direction D2 or the third direction D3).

[0051] The length L1 of the pair of internal electrodes 5, 6 in the second direction D2 is longer than the length L2 of the discharge auxiliary portion 7 in the second direction D2 (L1>L2). Because the internal electrodes 5, 6 are thick in this way, heat generation by the internal electrodes 5, 6 during discharge can be suppressed. This improves the durability of the transient voltage protection device 1. Furthermore, suppressing heat generation by the internal electrodes 5, 6 can suppress scattering of metal components of the discharge auxiliary portion 7. As a result, the possibility of short circuit occurrence can be reduced.

[0052] The protrusion 2g is provided so as to connect the main surface 5f and the main surface 6f to each other, which makes it possible to further suppress discharge at the portions of the tip surfaces 5b, 6b close to the main surfaces 5f, 6f.

[0053] The length L1 of the pair of internal electrodes 5, 6 in the second direction D2 is longer than the length L3 of the protrusion 2g in the second direction D2 (L1>L3), which prevents the protrusion 2g from interfering with discharge in the portions of the tip surfaces 5b, 6b closer to the main surfaces 5e, 6e.

[0054] The distance d1 between the main surfaces 5e and 6e is shorter than the distance d2 between the main surfaces 5f and 6f. This reduces the area of the discharge auxiliary part 7 exposed to the cavity S. This makes it possible to prevent the metal components contained in the discharge auxiliary part 7 from scattering. As a result, the possibility of a short circuit occurring can be reduced. Furthermore, because the distance d2 is longer than the distance d1, discharge can be further suppressed in the portions of the tip surfaces 5b and 6b near the main surfaces 5f and 6f.

[0055] The tip surfaces 5b, 6b are inclined with respect to the second direction D2. This makes it easy to achieve a configuration in which the area of the discharge auxiliary part 7 exposed to the cavity S is small. Furthermore, the inclination of the tip surfaces 5b, 6b makes it easier for the electric field to concentrate on the edges between the tip surfaces 5b, 6b and the main surfaces 5e, 6e. This makes it possible to further control the discharge location and makes it easier to induce discharge.

[0056] The present invention is not necessarily limited to the above-described embodiment, and various modifications are possible without departing from the spirit and scope of the present invention.

[0057] Fig. 5 is a cross-sectional view of a transient voltage protection device according to a modified example. As shown in Fig. 5, the transient voltage protection device 1A according to the modified example differs from the transient voltage protection device 1 in that the tip surfaces 5b, 6b are not inclined with respect to the second direction D2. In the transient voltage protection device 1A as well, the element body 2 has the protrusion 2g, so that discharge can be generated in the portions of the tip surfaces 5b, 6b closer to the main surfaces 5e, 6e rather than the portions closer to the main surfaces 5f, 6f.

[0058] In the transient voltage protection devices 1 and 1A, the tip surfaces 5b and 6b are each formed of a single plane, but may be curved surfaces or may be formed of a plurality of planes and have a step portion.

[0059] In the transient voltage protection device 1, 1A, the protrusion 2g does not have to be provided so as to connect the principal surface 5f and the principal surface 6f to each other. For example, the protrusion 2g may be provided in only a part of the region R when viewed from the second direction D2. Alternatively, multiple protrusions 2g may be provided. Even in such a case, the protrusion 2g increases the creepage distance in the portion of the tip surface 5b, 6b closer to the principal surfaces 5f, 6f. Therefore, discharge can be generated in the portion of the tip surface 5b, 6b closer to the principal surfaces 5e, 6e than in the portion of the tip surface 5b, 6b closer to the principal surfaces 5f, 6f.

[0060] In the transient voltage protection devices 1, 1A, the lengths L1 in the second direction D2 of the internal electrodes 5, 6 are equal to each other, but may be different from each other. In this case, the height positions of the principal surfaces 5f, 6f in the second direction D2 are different. The reference plane for the length L3 in the second direction D2 of the protrusion 2g can be set to one of the principal surfaces 5f, 6f closer to the side surface 2c. The shape of the insulator layer 12 is appropriately set to match the shape of the internal electrodes 5, 6.

[0061] In the transient voltage protection devices 1, 1A, the internal electrodes 5, 6 face each other in the first direction D1, but may face each other in the third direction D3. In this case, for example, the side surfaces 5d, 6d face each other with the cavity S interposed therebetween. [Explanation of symbols]

[0062] 1,1A...transient voltage protection device, 2...element body, 2g...protrusion, 3,4...external electrode, 5,6...internal electrode, 5b,6b...tip surface, 5e,6e...main surface, 5f,6f...main surface, 7...discharge auxiliary portion, D1...first direction, D2...second direction, S...cavity.

Claims

1. an element body having a cavity formed therein; a pair of internal electrodes extending along a first direction and provided within the element body so as to face each other across the cavity; a pair of external electrodes connected to corresponding internal electrodes of the pair of internal electrodes; a discharge auxiliary portion provided within the element body so as to be in contact with the pair of internal electrodes; Equipped with the pair of internal electrodes each have a first surface and a second surface facing each other in a second direction perpendicular to the first direction, and a third surface connecting the first surface and the second surface; the first surface is in contact with the discharge auxiliary part, the second surface is in contact with the element body, the third surface is exposed to the cavity; the element body has a protrusion that extends into the cavity from between the pair of second surfaces and is located between the pair of third surfaces, the second surface is a plane extending in the first direction; Transient voltage protection device.

2. The pair of internal electrodes face each other in the first direction.

10. The transient voltage protection device of claim 1.

3. The length of the pair of internal electrodes in the second direction is longer than the length of the discharge auxiliary portion in the second direction.

3. A transient voltage protection device according to claim 1 or 2.

4. The protrusion is provided to connect the pair of second surfaces to each other. A transient voltage protection device according to any one of claims 1 to 3.

5. The length of the pair of internal electrodes in the second direction is longer than the length of the protrusion in the second direction. A transient voltage protection device according to any one of claims 1 to 4.

6. The distance between the pair of first surfaces is shorter than the distance between the pair of second surfaces. A transient voltage protection device according to any one of claims 1 to 5.

7. the pair of third surfaces are inclined with respect to the second direction; 6. The transient voltage protection device of claim 5.

8. The lengths of the pair of internal electrodes in the second direction monotonically decrease as they move away from the connected external electrode of the pair of external electrodes in the first direction. A transient voltage protection device according to any one of claims 1 to 7.

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