Surge suppression component

Abstract

To provide a surge suppression component capable of suppressing the decline in reliability while maintaining a satisfactory inhibitory effect.SOLUTION: A surge suppression component 1 includes a base material 10 and at least a pair of electrodes. At least a part of the electrodes is placed on the surface or inside of the base material 10. The base material 10 includes a functional part 11 with a void between the pair of electrodes, which is made of polycrystalline material that shows voltage nonlinearity. At least one of the pair of electrodes includes multiple insulating particles 20 at least inside the electrode and near the interface between the electrode and the functional part 11.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a surge protection component, and more particularly to a surge protection component that absorbs surge current. [Background technology]

[0002] Patent Document 1 discloses a surge absorbing element. This surge absorbing element includes a first electrode, a second electrode provided opposite to the first electrode, and a ceramic layer having a polycrystalline structure composed of a plurality of crystal grains exhibiting voltage nonlinearity characteristics, at least a portion of which is in contact with the first electrode and the second electrode, and the ceramic layer has voids therein.

[0003] Patent Document 2 discloses an overvoltage protection component. This overvoltage protection component includes a first discharge electrode, a second discharge electrode, and an overvoltage protection unit formed between these electrodes, and the overvoltage protection unit contains a mixture of an insulating resin, conductive particles, and voltage nonlinear resistor particles. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2010 / 122732 [Patent Document 2] JP 2016-157896 A Summary of the Invention [Problem to be solved by the invention]

[0005] The surge absorption element of Patent Document 1 and the overvoltage protection component of Patent Document 2 can reduce the suppression effect, i.e., the suppression voltage, and can effectively cut off abnormal voltage, and are excellent in the ability to protect the protected object, but the surge absorption element of Patent Document 1 has an internal cavity structure, and the insulation reliability may be reduced due to the low resistance of the material in the cavity caused by thermal shock that occurs when a large current is applied during operation, and the overvoltage protection component of Patent Document 2 has a structure in which the electrodes face each other on the same plane, and when a large current is applied during operation, the electrodes wear out and the gap widens, which may increase the suppression voltage and reduce the suppression effect. Thus, these conventional surge protection components have the possibility of reducing reliability.

[0006] An object of the present disclosure is to provide a surge protection component that can suppress a decrease in reliability while maintaining a good suppression effect. [Means for solving the problem]

[0007] A surge protection component according to one aspect of the present disclosure includes an element body and at least a pair of electrodes. At least a portion of each of the pair of electrodes is disposed on a surface or inside of the element body. The element body includes a functional unit between the pair of electrodes, the functional unit being made of a polycrystalline material exhibiting voltage nonlinearity and having a gap. In at least one of the pair of electrodes, a plurality of insulating particles are present inside the electrode and at least one of the vicinity of the interface between the electrode and the functional unit. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide a surge protection component that can suppress a decrease in reliability while maintaining a good suppression effect. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view of a surge protection component according to a first embodiment of the present disclosure. [Diagram 2]FIG. 2 is a schematic cross-sectional view of the surge protection component according to the first embodiment of the present disclosure. [Diagram 3] FIG. 3 is a schematic cross-sectional view of the surge protection component according to the first embodiment of the present disclosure. [Figure 4] FIG. 4 is a schematic cross-sectional view of the surge protection component according to the first embodiment of the present disclosure. [Diagram 5] FIG. 5 is a schematic cross-sectional view of the surge protection component according to the first embodiment of the present disclosure. [Figure 6] FIG. 6 is a schematic cross-sectional view of the surge protection component according to the first embodiment of the present disclosure. [Figure 7] FIG. 7 is a schematic cross-sectional view of the surge protection component according to the first embodiment of the present disclosure. [Figure 8] FIG. 8 is a schematic cross-sectional view of a surge protection component according to a second embodiment of the present disclosure. [Figure 9] FIG. 9 is a schematic cross-sectional view of a surge protection component according to the second embodiment of the present disclosure. [Figure 10] FIG. 10 is a schematic cross-sectional view of a surge protection component according to a second embodiment of the present disclosure. [Figure 11] FIG. 11 is a schematic cross-sectional view of a surge protection component according to a third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] A surge protection component 1 according to an embodiment of the present disclosure will be described in detail. Note that the embodiment described below is merely an example of the present disclosure, and the present disclosure is not limited to the embodiment. Various modifications other than the embodiment are possible according to the design, etc., as long as they do not deviate from the technical idea of ​​the present disclosure. In addition, the following embodiments may be realized in appropriate combination.

[0011] (1) Overview An overview of the surge protection component 1 will now be given.

[0012] The surge protection component 1 includes an element body 10 and at least a pair of electrodes. There is usually a pair of electrodes (also referred to as a first electrode 31 and a second electrode 32), but there may be two or more pairs. At least a portion of each of the pair of electrodes 31, 32 is disposed on the surface or inside of the element body 10. Each of the pair of electrodes 31, 32 has two main surfaces with the largest areas and four end surfaces that are surfaces other than the main surfaces.

[0013] The element body 10 includes a functional part 11 between a pair of electrodes 31, 32. The functional part 11 is made of a polycrystalline body (hereinafter also referred to as polycrystalline body C) that exhibits voltage nonlinearity, and has voids. The functional part 11 usually has multiple voids. The polycrystalline body C includes multiple crystals and grain boundaries, and may be amorphous, single crystal, or twin crystal. The functional part 11 may also be made of a sintered body or a compact.

[0014] The pair of electrodes 31, 32 includes a functional part 11 between them, and at least a portion of the pair of electrodes 31, 32 may face each other via the functional part 11, or the end faces of the pair of electrodes 31, 32 may face each other via the functional part 11.

[0015] The surge protection component 1 of the present disclosure is characterized in that a plurality of insulating particles 20 are present in at least one of the pair of electrodes 31, 32, inside the electrodes 31, 32, and in at least one of the vicinity of the interface between the electrodes 31, 32 and the functional part 11. The term "insulating particles" refers to particles having a resistivity higher than that of polycrystalline body C. The resistivity of the insulating particles 20 can be measured by a nanoprober system on a cross section of the surge protection component 1 that has been mirror-polished and then dry-etched with CF4 gas. The measurement is performed by selecting any five or more insulating particles 20 in the polished cross section. The resistivity is obtained by placing the tips of two tungsten probes on each insulating particle 20 with an interval of 0.5 μm, applying a voltage of 10 V, and arithmetically averaging the results. The resistivity of polycrystalline body C is obtained by selecting any five points in polycrystalline body C from the polished cross section of surge protection component 1, applying a current of 5 μA to the points with the tips of two tungsten probes spaced 0.5 μm apart using a nanoprober system, and calculating the arithmetic average of the results obtained by applying a current of 5 μA. The resistivity may also be obtained from the material constants by performing elemental analysis (area analysis or point analysis) using elemental analysis EDS or EPMA on the cross section of surge protection component 1 prepared by polishing and then polishing with Ar ions using the cross section polisher (CP) method.

[0016] Furthermore, the surge protection component 1 usually includes at least a pair of external electrodes. There is usually a pair of external electrodes (also referred to as a first external electrode 41 and a second external electrode 42), but there may be two or more pairs.

[0017] The first external electrode 41 is usually provided on one end surface of the element body 10 and is electrically connected to the first electrode 31. The second external electrode 42 is usually provided on the other end surface of the element body 10 and is electrically connected to the second electrode.

[0018] The surge protection component 1 is mounted on a substrate, for example, by bonding the first external electrode 41 and the second external electrode 42 to the substrate using a bonding material such as solder. When a surge voltage is applied between the first external electrode 41 and the second external electrode 42 in a state where the surge protection component 1 is mounted on the substrate, a surge current flows through the functional part 11 between the first electrode 31 electrically connected to the first external electrode 41 and the second electrode 32 electrically connected to the second external electrode 42.

[0019] In the surge protection component 1 of the present disclosure, the functional part 11 arranged between the first electrode 31 and the second electrode 32 is made of polycrystalline bodies C exhibiting voltage nonlinearity, has voids, and has a plurality of insulating particles 20 present inside the first electrode 31 and the second electrode 32 and at least one of the vicinity of the interface between the first electrode 31 and the second electrode 32 and the functional part 11. The surge protection component 1 can improve insulation when a rated voltage is applied by having the plurality of insulating particles 20 present in this manner, and can improve the suppression effect by lowering the discharge start voltage, suppress thermal runaway due to heat generation during operation, and suppress the reduction in resistance of the polycrystalline bodies C in the voids of the functional part 11, and further suppress wear of the electrodes 31 and 32 due to the presence of the insulating particles 20. It is considered that the surge protection component 1 can suppress a decrease in reliability while maintaining a good suppression effect.

[0020] (2)Details <Surge protection components> The surge protection component 1 of this embodiment will be described in detail below with reference to the drawings. Note that each drawing described in the following embodiment is a schematic drawing, and the size and thickness ratios of each component in each drawing do not necessarily reflect the actual dimensional ratios.

[0021] In the surge protection component 1 of this embodiment, the element body 10 excluding the first external electrode 41 and the second external electrode 42 of the surge protection component 1 is formed into a rectangular parallelepiped shape with a length of 0.6 mm, a width of 0.3 mm, and a thickness of 0.3 mm, for example. The corners of the element body 10 may be appropriately chamfered, or the corners of the element body 10 may be rounded.

[0022] In the following description, the length direction of the element body 10 is referred to as the "X direction", the width direction as the "Y direction", and the thickness direction as the "Z direction". These directions are perpendicular to each other. However, these directions are merely examples, and are not intended to specify the directions in which the surge protection component 1 is used.

[0023] Examples of the surge protection component 1 of this embodiment include a first embodiment, a second embodiment, and a third embodiment described below. First embodiment: A pair of electrodes 31, 32 are arranged inside the element body 10 such that at least parts of their main surfaces face each other via the functional section 11 (hereinafter also referred to as arrangement I). Second embodiment: A pair of electrodes 31, 32 are arranged so that their end faces face each other with the functional section 11 interposed therebetween (hereinafter, also referred to as arrangement II). Third embodiment: The electrodes 31, 32 have both configurations I and II. Each embodiment will be described below.

[0024] [First embodiment] As shown in FIG. 1, in the surge protection component 1 of the first embodiment, a pair of electrodes are arranged inside the element body 10 as a pair of internal electrodes 31, 32 in which at least parts of their main surfaces face each other via a functional section 11 (arrangement I).

[0025] The surge protection component 1 of the first embodiment can improve insulation when a rated voltage is applied, and can suppress a decrease in resistance of the polycrystalline bodies C in the gaps due to suppression of thermal runaway caused by heat generation during operation, thereby further suppressing a decrease in reliability. The surge protection component 1 of the first embodiment can be suitably used as, for example, a surge absorbing element.

[0026] Hereinafter, each component of the surge protection component 1 of the first embodiment will be described.

[0027] [Internal electrode] 1, the first internal electrode 31 and the second internal electrode 32 are provided facing each other inside the element body 10. The first internal electrode 31 and the second internal electrode 32 are provided so that at least a portion of them faces each other via the functional section 11. The first internal electrode 31 and the second internal electrode 32 preferably have a thickness of 5 μm or more. By providing such a thickness, it is possible to prevent the internal electrodes from being burned away due to discharge and to improve resistance to static electricity.

[0028] The first internal electrode 31 and the second internal electrode 32 include, for example, an Ag-Pd alloy. The first internal electrode 31 and the second internal electrode 32 may include at least one of Pd, Au, Ag, Pt, and the like.

[0029] The first internal electrode 31 and the second internal electrode 32 are, for example, rectangular in shape with the X direction as the longitudinal direction and the Y direction as the transverse direction. The shape and the area of ​​the opposing portions are appropriately designed in accordance with the distance between the first internal electrode 31 and the second internal electrode 32 and the thickness of the functional section 11 according to the capacitance of the surge protection component 1. The longitudinal and transverse dimensions of the first internal electrode 31 and the second internal electrode 32 are determined by arithmetic averages of measurements taken at five or more points on any five cross sections selected in the surge protection component 1. In the first embodiment, the shapes of the first internal electrode 31 and the second internal electrode 32 are rectangular in shape with a length of 380 μm in the X direction and a length of 85 μm in the Y direction so that the capacitance of the surge protection component 1 is 0.05 to 0.2 pF. The portion where the first internal electrode 31 and the second internal electrode 32 are opposing has a length of 160 μm in the X direction and a length of 82 μm in the Y direction. Although it depends on the process and the precision of the equipment, since the repeat printing precision is generally within 10 μm and the lamination precision is within 10 μm, a difference of within 20 μm from the design value is acceptable. In the first embodiment, a difference of 20 μm or more is used as the standard for judging the size of the shape. However, this is not limited to the case where a more precise process or equipment is used.

[0030] As shown in FIG. 1, each of the first internal electrode 31 and the second internal electrode 32 has a first surface S1 that faces each other, and a second surface S2 that is on the opposite side to the first surface S1 and does not face each other.

[0031] [External electrode] The first external electrode 41 and the second external electrode 42 are provided so as to be in contact with the surface of the element body 10. In detail, the first external electrode 41 is provided so as to cover one entire end face of the element body 10, two side faces adjacent to this end face, and one end of each of the two main faces. The second external electrode 42 is provided so as to cover the other entire end face of the element body 10, two side faces adjacent to this end face, and the other end of each of the two main faces.

[0032] The first external electrode 41 and the second external electrode 42 include a conductive metal such as silver (Ag). The conductive metal may include at least one of Cu, Ni, Pd, an Ag-Pd alloy, Au, and the like. In addition, it is preferable that the first external electrode 41 and the second external electrode 42 do not include resin. With such a configuration, even when static electricity or the like is applied, a large current can be instantaneously passed and heat generation can be suppressed, thereby improving the reliability of the surge protection component 1. The first external electrode 41 and the second external electrode 42 may be formed by plating. In addition, plated electrodes may be formed on the first external electrode 41 and the second external electrode 42.

[0033] The first external electrode 41 and the second external electrode 42 are formed by applying a paste of powder such as Ag to one and the other ends of the element body 10 and then subjecting it to a heat treatment.

[0034] The first external electrode 41 and the second external electrode 42 (primary external electrode) may include a secondary external electrode that covers at least a part of the primary external electrode. The thickness of the thickest part of the primary external electrode is, for example, 20 to 200 μm, but is not limited to this. When suppression of high voltage or higher repetition resistance is required, the primary external electrode is preferably 100 μm or more. With such a configuration, it is possible to suppress burnout when a large current is applied. In the first embodiment, the thickness is about 120 μm. The secondary external electrode may include a resin such as an amino resin such as an epoxy resin or a urea resin, a phenolic resin such as a resol type or a novolac type, or a silicone-modified organic resin such as a silicone epoxy. Specifically, the secondary external electrode may include an epoxy resin and a conductive metal such as Ag. The secondary external electrode may further include, as an additive, a low-melting point metal having a melting point lower than that of the conductive metal such as Ag. Examples of the low-melting point metal include metals such as Sn, In, and Pb having a melting point of 400° C. or less. The secondary external electrode is formed by applying a paste made by mixing epoxy resin in a fluid state before hardening, conductive metal powder, and a low-melting point metal onto the primary external electrode, and then heat treating it. By configuring the secondary external electrode in this way, the effect of alleviating internal and external stress is obtained, and the resistance of the surge protection component 1 to repeated application of static electricity and the mounting reliability can be improved. A nickel layer and a tin layer may be formed in sequence on the surface of this secondary external electrode by electroplating.

[0035] [Base body] 1, the element 10 has a functional portion 11 and an outer peripheral portion 12. The outer peripheral portion 12 covers the functional portion 11. The main component of the functional portion 11 is usually different from the main component of the outer peripheral portion 12.

[0036] Moreover, the outer peripheral portion 12 has a smaller porosity than the functional portion 11. That is, the porosity of the functional portion 11 is larger than the porosity of the outer peripheral portion 12. By making the porosity of the functional portion 11 larger than that of the outer peripheral portion 12, the surge protection component 1 can selectively discharge at the functional portion 11, and the reliability can be further improved. The "porosity" of the functional portion 11 or the outer peripheral portion 12 refers to the ratio of the total volume of voids to the volume of the functional portion 11 or the outer peripheral portion 12. The porosity can be obtained by calculating the ratio of the area occupied by voids in a polished cross section of the functional portion 11 or the outer peripheral portion 12. For example, the polished cross section is prepared by Ar ion polishing using a cross-section polisher (CP) method, and the area ratio occupied by voids is calculated from the observation of the polished cross section. The porosity is measured by performing the measurement at any five or more points for each of the functional portion 11 and the outer peripheral portion 12 in the cross section of the central portion of the surge protection component 1, and calculating the arithmetic average value of these measured values.

[0037] (Outer periphery) The main component of the outer peripheral part 12 includes, for example, glass ceramics. When the outer peripheral part 12 includes an element having a smaller work function than the functional part 11, discharge at a low voltage is possible, and the surge absorption effect can be further improved. The "work function" means the minimum energy required to extract electrons in a solid into a vacuum. Discharge is promoted by including an element having a small work function on the surface of the outer peripheral part 12 on the functional part 11 side. The glass ceramic may be, for example, a low-temperature fired ceramic including alumina particles and borosilicate glass. In the first embodiment, glass ceramics (relative dielectric constant is about 10) in which MgO, SiO2, and Gd2O3 are added to alumina particles and borosilicate glass is used. In this way, by configuring the outer peripheral part 12 to include an element having a small relative dielectric constant and a small work function, discharge is promoted and the capacitance of the surge protection component 1 can be reduced, making it an element suitable for application to high-speed communication circuits.

[0038] The porosity of the outer circumferential part 12 is preferably 20% or less, and is, for example, 6%. With such a configuration, the mechanical strength of the surge protection component 1 is maintained good, and discharge can be more selectively performed in the functional part 11, thereby further improving reliability.

[0039] (Functional part) The first internal electrode 31 and the second internal electrode 32 face each other with at least a portion thereof interposing the functional portion 11 therebetween. That is, the functional portion 11 is provided inside the element body 10 between the first internal electrode 31 and the second internal electrode 32 that are arranged facing each other in the Z direction. It is preferable that at least a portion of the functional portion 11 contacts at least one of the first internal electrode 31 and the second internal electrode 32, and it is more preferable that the functional portion 11 contacts both the first internal electrode 31 and the second internal electrode 32.

[0040] The functional part 11 is made of a polycrystalline body C having a voltage nonlinear characteristic, i.e., a nonlinear voltage dependency of the resistance value, and has voids. The polycrystalline body C constituting the functional part 11 usually has a plurality of voids that communicate within the functional part 11 from the first internal electrode 31 side to the second internal electrode 32 side. In detail, when the voltage applied to the functional part 11 is lower than a predetermined voltage value, no current flows, and when a surge voltage equal to or higher than the predetermined voltage value is applied to the functional part 11, a creeping discharge occurs along the voids of the polycrystalline body C, causing a surge current to flow. This allows the functional part 11 to absorb the surge current.

[0041] The polycrystalline body C constituting the functional part 11 contains, for example, ZnO as a main component. The functional part 11 also contains elements such as Sr, Ca, Co, Cr, Mn, and Al as secondary components. The functional part 11 contains a crystal mainly composed of ZnO and a grain boundary containing at least a part of the secondary component. This secondary component exhibits characteristics as a p-type semiconductor and forms a barrier at the interface with ZnO, which is an n-type semiconductor. These secondary components may also be present as a solid solution of a perovskite structure of the composition formula ABO3 at the grain boundary of the ZnO crystal. Here, the A site is at least one of alkaline earth metals Sr, Ca, and Ba, and the B site is at least one of transition metals Co, Mn, and Cr. In this way, the polycrystalline body C contains an element with a melting point higher than that of ZnO, thereby improving thermal stability and surge resistance. A film of the composition of the first external electrode 41 and the second external electrode 42 may be provided on a part of the outer periphery of the polycrystalline body C constituting the functional part 11. With such a configuration, it is possible to increase the adhesion between the crystals and improve the structural stability of the polycrystalline body C. The thickness of the functional part 11 in the Z direction is appropriately changed depending on the desired suppression voltage. For example, by setting the thickness of the functional part 11 in the Z direction to be 2 μm or more and 60 μm or less, better surge absorption characteristics can be achieved. For example, in the first embodiment, it is 12 μm.

[0042] It is preferable that the functional part 11 does not substantially contain a rare gas. In this case, the short circuit prevention effect can be further improved. If the functional part 11 contains a rare gas, continuous application of a high voltage may lead to a state in which discharge continues, i.e., a short circuit continues, making it difficult to suppress repeated surges. In that case, the surge protection component 1 operates even at a circuit operating voltage that does not require suppression, thereby hindering the operation of the circuit. "Substantially free" means that the substance is not actively added, except in cases where it is unavoidably mixed in. Specifically, the partial pressure of the rare gas is 1% or less of the total gas contained in the functional part 11. The rare gas is a gas of an element belonging to Group 18 of the periodic table, and examples of such gas include helium, argon, neon, krypton, and xenon. When an electric field of about 500 V / mm is applied to argon at atmospheric pressure, it leads to continuous aerial discharge, thereby hindering the operation of the circuit to be protected. The discharge inception voltage increases as the partial pressure of argon gas decreases. The discharge start voltage of air is about 3 kV / mm, and unlike argon, it does not lead to continuous discharge. Air contains about 1% argon. In other words, if the partial pressure of the rare gas is 1% or less of the total gas contained in the functional part 11, stable repeated operation is possible.

[0043] The porosity of the functional part 11 is preferably 25% to 92%, for example, 85%. By setting the porosity of the functional part 11 within the above range, the structure in the polycrystalline body C can be connected, the functional part 11 can function as a discharge mechanism, and better surge resistance can be obtained.

[0044] (Insulating particles) The resistivity of the insulating particles 20 is greater than the resistivity of the polycrystalline body C of the functional portion 11 .

[0045] As shown in FIG. 1, in the surge protection component 1, multiple insulating particles 20 are present inside the first internal electrode 31 and the second internal electrode 32, and at least one of the vicinity of the interface between the first internal electrode 31 and the second internal electrode 32 and the functional section 11.

[0046] The insulating particles 20 may be uniformly dispersed within the first internal electrode 31 and the second internal electrode 32, or in the region near the interface between the first internal electrode 31 and the second internal electrode 32 and the functional section 11, or may be concentrated in a specific region.

[0047] As shown in Fig. 2, the insulating particles 20 are preferably present inside the first internal electrode 31 and the second internal electrode 32. In this case, the insulating particles 20 reduce the shrinkage rate of the first internal electrode 31 and the second internal electrode 32 during the sintering process, and thus have the effect of preventing structural defects between the functional part 11 and the outer peripheral part 12 and the first internal electrode 31 and the second internal electrode 32. This makes it possible to form the first internal electrode 31 and the second internal electrode 32 thick, preventing the internal electrodes from disappearing due to discharge, and improving resistance to static electricity.

[0048] As shown in FIG. 3, the insulating particles 20 are preferably unevenly distributed on the first surfaces S1 of the first internal electrode 31 and the second internal electrode 32, which face each other. In this case, the insulating particles 20 are interposed between the first surfaces S1 of the first internal electrode 31 and the second internal electrode 32, which face each other, and the functional part 11, thereby improving the insulation when the rated voltage is applied, and further preventing the insulation resistance of the surge protection component 1 from decreasing due to thermal damage of the functional part 11 caused by static electricity. The insulation resistance of the surge protection component 1 is, for example, a resistance value when DC 0.1 V is applied, and is preferably 1 kΩ or more in applications without DC application, and 1 MΩ or more under the rated voltage application in applications with the rated voltage application. In addition, when the work function of the insulating particles 20 is smaller than that of the functional part 11, discharge is promoted, and the suppression voltage can also be reduced. Furthermore, when the thermal conductivity of the insulating particles 20 is higher than that of the functional part 11, heat dissipation to the first internal electrode 31 and the second internal electrode 32 is promoted, thermal damage to the functional part 11 is prevented, and the effect of preventing insulation deterioration of the surge protection component 1 is also obtained. In addition, it is preferable that the insulating particles 20 are present more on the mutually opposing first surface S1 side of the first internal electrode 31 and the second internal electrode 32 than on the mutually not opposing second surface S2 side of the first internal electrode 31 and the second internal electrode 32. Furthermore, it is more preferable that the insulating particles 20 are not present on the mutually not opposing second surface S2 side of the first internal electrode 31 and the second internal electrode 32. In this case, the bonding property between the mutually opposing first surface S1 side of the first internal electrode 31 and the second internal electrode 32 and the outer circumferential part 12 is selectively improved, and it is possible to prevent the surge protection component 1 from breaking from the functional part 11 due to internal stress generated by heat generation when static electricity is applied.

[0049] On the other hand, when static electricity is continuously applied and the heat generation amount of the functional part 11 becomes large, the insulating particles 20 may be present on the second surface S2 side of the first internal electrode 31 and the second internal electrode 32, which do not face each other. In addition, it is preferable that the insulating particles 20 are present more on the second surface S2 side of the first internal electrode 31 and the second internal electrode 32, which do not face each other, than on the first surface S1 side of the first internal electrode 31 and the second internal electrode 32, which face each other. It is preferable that the insulating particles 20 are unevenly distributed on the second surface S2 side of the first internal electrode 31 and the second internal electrode 32, which do not face each other. Furthermore, it is more preferable that the insulating particles 20 are not present on the first surface S1 side of the first internal electrode 31 and the second internal electrode 32, which face each other. In this case, it is preferable that the insulating particles 20 have a high thermal conductivity. With this configuration, the anchor effect increases the bonding strength between the second surface sides of the first internal electrode 31 and the second internal electrode 32 and the outer circumferential portion 12, and the heat dissipation is promoted, improving resistance to thermal shock.

[0050] Furthermore, the insulating particles 20 may be present on the side (S3) of the first surface S1 and the second surface S2 of the first internal electrode 31 and the second internal electrode 32, which is perpendicular to the first surface S1 and the second surface S2. That is, the first internal electrode 31 and the second internal electrode 32 have ends at the ends in a direction perpendicular to the direction in which the first internal electrode 31 and the second internal electrode 32 face each other, and the insulating particles 20 may be present on the end side. In addition, it is preferable that the insulating particles 20 are unevenly distributed on the end side of the first internal electrode 31 and the second internal electrode 32. With this configuration, the first internal electrode 31 and the second internal electrode 32 are prevented from diffusing to the outer periphery 12. With this effect, it is possible to prevent a current path caused by a decrease in resistance between the first external electrode 41 and the second external electrode 42 and the first internal electrode 31 and the second internal electrode 32, and the reliability of the surge protection component 1 can be further improved.

[0051] As shown in FIG. 4, the insulating particles 20 are preferably unevenly distributed in the area where the first internal electrode 31 and the second internal electrode 32 overlap when viewed from the direction in which the first internal electrode 31 and the second internal electrode 32 face each other (Z direction). In this case, the effective volume through which the current flows is increased in the first internal electrode 31 and the second internal electrode 32 other than the area where the first internal electrode 31 and the second internal electrode 32 overlap, so that a higher suppression effect can be obtained. In addition, a short circuit prevention effect is also obtained in the area where the first internal electrode 31 and the second internal electrode 32 overlap. The insulating particles 20 are "distributed unevenly in the area where the pair of internal electrodes overlap" means that the amount of insulating particles is greater in the area where the internal electrodes overlap than in areas other than the area where the internal electrodes overlap. In addition, in such a case, as shown in FIG. 5, it is more preferable that the insulating particles 20 are unevenly distributed on the center side of the area where the first internal electrode 31 and the second internal electrode 32 overlap. In this case, if a material with high thermal conductivity is used for the insulating particles 20, heat generated when static electricity is applied can be dissipated from inside the surge protection component 1, which is more effective in preventing insulation deterioration. The insulating particles 20 being "distributed unevenly toward the center" means that in the region where the internal electrodes overlap, the amount of insulating particles 20 is greater in the region closer to the outer periphery 12 than in the center in the X direction.

[0052] In addition, when viewed from the direction in which the first internal electrode 31 and the second internal electrode face each other (Z direction), it is also preferable that the insulating particles 20 are unevenly distributed outside the region where the first internal electrode 31 and the second internal electrode 32 overlap each other. For example, when the first internal electrode 31 and the second internal electrode 32 are formed thick or a plurality of internal electrodes are formed, if there is a possibility of a structural defect occurring at the end face of the element body 10, the anchor effect improves the bonding strength between the first internal electrode 31 and the second internal electrode 32 and the outer periphery 12, and the surge protection component 1 is prevented from breaking. The insulating particles 20 being "distributed unevenly outside the region where the pair of internal electrodes overlap" means that the amount of insulating particles is greater in the region other than the region where the internal electrodes overlap than in the region where the internal electrodes overlap. In such a case, it is more preferable that the insulating particles 20 are unevenly distributed in the vicinity of the external electrodes 41 and 42 of the internal electrodes 31 and 32 as shown in FIG. 6. In this case, when plating the first external electrode 41 and the second external electrode 42, a short circuit in the functional part 11 caused by the infiltration of plating liquid from the end face of the element body 10 can be prevented, and the reliability of the surge protection component 1 can be further improved.

[0053] The surge protection component 1 of the first embodiment also includes a component including a plurality of pairs of a first internal electrode 31 and a second internal electrode 32, as shown in FIG.

[0054] Examples of the form in which the insulating particles 20 are present include those attached to the surfaces of the pair of internal electrodes 31 and 32, those exposed to the surfaces of the pair of internal electrodes 31 and 32, those embedded inside the pair of internal electrodes 31 and 32, and those present near the interface between the pair of internal electrodes 31 and 32 and the functional section 11. A diffusion layer may be present at the interface between the insulating particles 20 and the functional section 11 or at the interface between the insulating particles 20 and the internal electrodes 31 and 32. The diffusion layer refers to a location where the components contained in the insulating particles 20 and the conductive metals of the internal electrodes 31 and 32 coexist, or a location where a reaction product of the components contained in the insulating particles 20 and the conductive metals of the internal electrodes 31 and 32 is generated. The diffusion layer can be confirmed by elemental analysis using an energy dispersive X-ray spectrometer (EDS) or an electron probe microanalyzer (EPMA).

[0055] 1 and the like, the insulating particles 20 have a substantially spherical or substantially elongated spheroid shape, but preferably have a scale shape or a surface irregular shape. The "surface irregular shape" means that irregularities are formed on the surface of the insulating particles 20. By having such a shape, the insulating particles 20 can be more easily interposed between the polycrystalline body C, which is in the vicinity of the interface between the pair of internal electrodes 31, 32 and the functional part 11, and the DC resistance can be further improved.

[0056] When the insulating particles 20 have an uneven surface, they exert an anchor effect at the interface with the polycrystalline body C, improving the stability of the functional part 11 as a structure. In addition, in this case, the connectivity during powder compaction is improved, and the heat dissipation effect due to the enlarged surface area is improved. Therefore, when a surge is continuously applied, heat dissipation inside the surge protection component 1 is promoted, so that thermal destruction such as melting of the functional part 11 due to heat generation can be prevented, and reliability can be improved. It is preferable that the convex parts of the insulating particles 20 have low crystallinity, and the concave surfaces have high crystallinity. In this case, the convex parts have low hardness and high deformability, whereas the concave parts are hard and difficult to deform. Therefore, the deformation of the convex parts during powder compaction improves the bonding at the particle interface, and the structure of the functional part 11 becomes stronger. The unevenness can be formed on the surface of the insulating particles, for example, by using a surface modification device (for example, "Nobilta" manufactured by Hosokawa Micron Corporation) that selectively applies shear stress to the particle surface in a dry manner. The crystallinity of the particle surface can be compared by the peak half-width in a micro X-ray diffraction pattern. It can also be compared by observing lattice images with a transmission electron microscope (TEM). Insulating particles 20 with an uneven surface have a larger surface area and higher heat dissipation properties compared to other shapes. In applications where surge protection component 1 is continuously loaded, it promotes heat dissipation inside surge protection component 1, thereby suppressing thermal destruction such as melting of functional part 11 due to heat generation and further improving reliability.

[0057] The ratio of the total volume of the insulating particles 20 is preferably 3% by volume or more, and more preferably 25% by volume or more, relative to the total volume of the metal contained in the internal electrodes 31, 32. In this case, the insulating particles 20 are more uniformly dispersed, and the effect of preventing short circuits when the rated voltage is applied is more obtained. The ratio of the total volume of the insulating particles 20 is preferably 70% by volume or less, and more preferably 45% by volume or less, relative to the total volume of the metal contained in the internal electrodes 31, 32. In this case, the aggregation of the insulating particles 20 and the effect on the sintering property of the functional part 11 are not apparent, and the effect of preventing short circuits and mechanical reliability can be further improved.

[0058] The average diameter of the insulating particles 20 is preferably smaller than the average diameter of the polycrystalline body C in the functional part 11. In this case, the insulating particles 20 are more likely to appear on the surface of the polycrystalline body C in the functional part 11, thereby reducing the discharge start voltage and further improving the insulation reliability.

[0059] It is also preferable that the average diameter of the insulating particles 20 is larger than the average diameter of the polycrystalline bodies C in the functional part 11. In this case, the insulating particles 20 can be easily interposed between the polycrystalline bodies C in the functional part 11, and the DC resistance of the surge protection component 1 can be further improved, making it suitable for use in applications where DC resistance is required.

[0060] The "average diameter" of the insulating particle 20 or the polycrystalline body C means the arithmetic mean diameter calculated by the intercept method for each of the insulating particle 20 or the polycrystalline body C in any five polished cross sections including the functional part 11. The polished cross sections are prepared by Ar ion polishing using a cross-section polisher (CP) method.

[0061] The melting point of the insulating particles 20 is preferably higher than the melting point of the polycrystalline body C and the melting point of the metal contained in the internal electrodes 31, 32. In this case, it is possible to further improve the durability against heat generated by application during operation, and therefore the surge protection component 1 can further improve the insulation reliability.

[0062] The insulating particles 20 preferably contain an oxide of at least one element selected from the group consisting of B, Al, Y, Nd, Sm, Dy, Ca, Sr, Ba, Co, and Mg. When the insulating particles 20 contain such a substance with a low work function, the surge protection component 1 can further lower the suppression voltage and further improve the suppression effect, and can be suitably used even when a high suppression effect is required.

[0063] Moreover, the insulating particles 20 preferably contain an oxide, a nitride, a carbide, or a combination thereof of at least one element selected from the group consisting of Al, Zr, Y, and Si. When the insulating particles 20 contain such a highly heat dissipating substance, the surge protection component 1 can further improve the heat dissipation, and therefore the insulation reliability can further be improved.

[0064] The work function of the insulating particles 20 is preferably smaller than that of the polycrystalline C in the functional portion 11. In this case, the surge protection component 1 can promote discharge and further improve the suppression effect, and can be suitably used even when a high suppression effect is required. When the functional portion 11 is mainly composed of ZnO (work function: 3.0 to 4.3 eV), examples of materials having such a work function include Y2O3 (2.0 eV), Nd2O3 (2.3 eV), Dy2O3 (2.1 eV), CaO (1.6 eV), SrO (1.3 eV), BaO (1.1 eV), and Gd2O3 (2.1 eV).

[0065] It is also preferable that the work function of the insulating particles 20 is larger than that of the polycrystalline body C in the functional section 11. In this case, the suppression voltage can be adjusted without changing the element design such as the thickness of the functional section 11, and insulation reliability can be maintained even when a high rated voltage is required. When the functional section 11 is mainly composed of ZnO, examples of materials having such a work function include Al2O3 (4.7 eV), MgO (4.7 eV), and ZrO2 (5.8 eV).

[0066] The thermal conductivity of the insulating particles 20 is preferably higher than that of the polycrystalline body C in the functional part 11. In this case, the discharge starting voltage can be controlled, and the surge protection component 1 can be selected according to the operating voltage of the object to be protected. When the functional part 11 is mainly composed of ZnO (thermal conductivity: 25 to 40 W / m·K), examples of materials having such thermal conductivity include Al2O3 (30 to 35 W / m·K), MgO (60 W / m·K), BN (170 W / m·K), SiC (150 W / m·K), AlN (170 W / m·K), Si3N4 (28 W / m·K), etc.

[0067] It is also preferable that the thermal conductivity of the insulating particles 20 is smaller than that of the polycrystalline body C in the functional part 11. In this case, it is possible to suppress the occurrence of breakage of the surge protection component 1 caused by heat shock. When the functional part 11 is mainly composed of ZnO, examples of materials having such thermal conductivity include ZrO2 (3 W / m·K), SiO2 (1.4 W / m·K), Y2O3 (14 W / m·K), Si3N4 (28 W / m·K), cordierite (2MgO·2Al2O3·5SiO2) (2 W / m·K), etc.

[0068] [Second embodiment] In the surge protection component 1 of the second embodiment, a pair of electrodes 31, 32 are arranged on the surface of the outer periphery 12 of the element body 10 so that their end faces face each other with the functional part 11 interposed therebetween (arrangement II). In the surge protection component 1 of FIG. 8, the pair of electrodes 31, 32 are provided on the same plane. According to the surge protection component 1 of the second embodiment, wear of the electrodes 31, 32 can be further suppressed, thereby making it possible to further maintain reliability. The surge protection component 1 of the second embodiment can be suitably used as, for example, an ESD suppressor.

[0069] The surge protection component 1 of the second embodiment differs from the surge protection component 1 of the first embodiment in that the pair of electrodes 31, 32 are arranged with their end faces facing each other (arrangement II) and that the pair of electrodes 31, 32 may be present on the surface of the element body 10, but the other components are the same. In the surge protection component 1 of the second embodiment, the polycrystalline body C constituting the functional part 11 usually has a plurality of voids that connect the functional part 11 from the first electrode 31 side to the second electrode 32 side.

[0070] In the surge protection component 1 of the second embodiment, the pair of electrodes 31, 32 may be arranged so long as their end faces face each other via the functional portion 11, and the pair of electrodes 31, 32 may be arranged on different planes rather than on the same plane, as shown in Fig. 9. With this configuration, the distance between the facing electrodes 31, 32 can be adjusted, and the discharge voltage can be controlled.

[0071] The surge protection component of the second embodiment also includes one in which a pair of electrodes 31, 32 are disposed inside the element body 10, as shown in FIG.

[0072] [Third embodiment] As shown in FIG. 11, the surge protection component 1 of the third embodiment has the arrangement of a pair of electrodes 31, 32 in both the arrangement (arrangement I) of the first embodiment and the arrangement (arrangement 2) of the second embodiment.

[0073] The surge protection component 1 of the third embodiment differs from the surge protection components 1 of the first and second embodiments in that it has both arrangement I and arrangement II for at least one pair of electrodes, but the other components are the same.

[0074] The surge protection component 1 of the third embodiment can improve insulation when the rated voltage is applied, suppress thermal runaway caused by heat generation during operation, thereby suppressing a decrease in resistance of the polycrystalline body C, and suppress wear of the electrodes 31 and 32, thereby further suppressing a decrease in reliability.

[0075] <Manufacturing method for surge protection components> A method for manufacturing the surge protection component 1 of this embodiment will be described.

[0076] First, the insulating particles 20 are prepared. In this embodiment, glass ceramics obtained by adding BaO, SiO2, MgO, and Gd2O3 to alumina particles and borosilicate glass are used as the insulating particles 20. The particle diameter of the insulating particles 20 can be, for example, 0.1 to 5 μm. Preferably, the particle diameter of the insulating particles 20 is one-third or less of the thickness of the functional part. By adopting such a configuration, the insulating particles 20 can be uniformly dispersed, and higher reliability can be achieved. In addition, the particle shape of these particles may be any shape, such as spherical, needle-like, scale-like, and hollow particles. When a high rated voltage is required, the insulating reliability is improved by uniformly distributing the insulating particles 20, so the particle shape is preferably spherical. When a higher ESD resistance (repeated application) is required, the particle diameter of the raw material of the insulating particles 20 is preferably needle-like or scale-like. The insulating particles 20 having these particle shapes are likely to have their longitudinal direction parallel to the internal electrodes (31, 32) in the functional part. Therefore, the heat dissipation is improved in the X and Y directions, which reduces the load in the Z direction, and the electrode thickness can be increased, preventing interface peeling between the electrodes (31, 32) and the functional part 11, and solder cracks. In addition, in cases where a high-voltage ESD of 20 kV or more is applied only once, it is preferable to use particles with a high porosity such as hollow particles as a raw material, since the heat capacity of the insulating particles 20 can be reduced to prevent the surge protection component 1 from being destroyed by heat shock. The insulating particles 20 may have an uneven surface, that is, the surface may have unevenness. By using the insulating particles 20 having an uneven surface, the surge protection component 1 can improve the connectivity during powder molding and improve the heat dissipation by expanding the surface area. Therefore, when a surge is continuously applied, heat dissipation inside the surge protection component 1 is promoted, preventing thermal destruction such as melting of the functional part 11 due to heat generation, and improving reliability. Since the effects of the shapes of the insulating particles 20 are independent, it is also possible to obtain the effect of combining them.

[0077] The insulating particles 20 are uniformly mixed with a metal such as an Ag-Pd alloy, Pd, Au, Ag, or Pt, an organic binder, and a solvent to prepare a conductive paste. The conductive paste forms a conductive base that will become the internal electrodes 31 and 32 after firing, which will be described later.

[0078] Next, the ceramic powder exhibiting the voltage nonlinearity characteristic, the organic binder, the solvent, and more preferably, the resin particles are mixed uniformly. In this case, the insulating particles 20 may be added. In this manner, the voltage nonlinearity ceramic slurry or ceramic paste for forming the functional part 11 is prepared. The composition of the ceramic powder used in this embodiment is 97.5 mol % of ZnO as the main component, and 2.5 mol % of elements such as Sr, Ca, Co, Cr, Mn, and Al as other subcomponents, thereby realizing a configuration with a high suppression effect. Furthermore, the ceramic powder exhibiting the voltage nonlinearity characteristic may be coated with conductive elements such as Ag-Pd alloy and Ag by vapor deposition, mechanical bonding, electroless plating, or the like. By adopting such a configuration, the stability of the porous structure in the functional part 11 can be improved.

[0079] The ceramic slurry or ceramic paste may contain a plasticizer or the like. The resin particles are formed of a polymeric material that completes thermal decomposition at approximately 600°C or less, and preferably a thermoplastic resin is used. The resin particles may be at least one of a spherical shape or an elliptical shape, and may be a true sphere. Examples of the spherical or elliptical shape include particles in which the ratio of the longest diameter to the shortest diameter is 1.25 or less for 95% or more of the number of particles. In this embodiment, spherical acrylic resin particles are used to obtain the effect of improving dispersibility during paste mixing. The porosity of the functional part 11 can be controlled by adjusting the amount of thermoplastic resin added. The functional part 11 can be formed by using this ceramic slurry or ceramic paste.

[0080] Next, an outer layer green sheet and a conductive paste for forming a conductive base are prepared. After firing, which will be described later, the outer layer green sheet becomes the outer peripheral portion 12. The outer layer green sheet is a glass ceramic sheet containing alumina particles and borosilicate glass, and has a relative dielectric constant of about 10 after firing. With this configuration, the stray capacitance of the surge protection component 1 can be reduced. The alumina particles and borosilicate glass are mixed with La2O3, CeO2, Pr6O 11 Alternatively, at least one of Nd2O3, Sm2O3, MgO, SiO2, and Gd2O3 may be added. In the present embodiment, glass ceramics in which MgO, SiO2, and Gd2O3 are added to alumina particles and borosilicate glass are used. In this way, by configuring the outer peripheral portion 12 to include an element with a small work function, discharge is promoted and the protective effect is improved.

[0081] Next, a conductive paste is applied on the outer layer green sheet by screen printing or the like and dried to form a thin conductive base having a predetermined shape. After firing, which will be described later, the conductive base becomes the internal electrodes 31 and 32. In this embodiment, an Ag-Pd alloy (Ag / Pd ratio: 70 / 30) is used as the internal electrode material, making it possible to perform heat treatment in the atmosphere. The locations where the insulating particles 20 are unevenly distributed in the surge protection component 1 can be controlled by preparing several types of conductive paste with different contents of the insulating particles 20 and printing using a screen plate patterned with a predetermined printing location. Next, a nonlinear voltage characteristic ceramic green body and an outer layer green sheet are formed on the outer layer green sheet and the conductive base. The nonlinear voltage characteristic ceramic green body becomes the functional part 11 after firing.

[0082] In the above-described manufacturing method, the conductive paste is applied by printing, but the method is not limited to this. As the printing method, for example, a doctor blade method, a calendar method, a spin coating method, a dip coating method, an inkjet method, an offset method, a die coating method, a spray method, etc. may be used.

[0083] The ceramic green body contains a plurality of resin particles and is formed on a conductive substrate by forming a ceramic slurry by a doctor blade method, a reverse roll coater method, or the like, or by forming a ceramic paste by screen printing, gravure printing, or the like.

[0084] Next, the laminate is heated to a temperature at which the organic binder and resin particles can be eliminated, and the laminate is heat-treated to decompose and remove the organic binder and resin particles contained in the ceramic green body, forming the functional part 11 having voids. In this embodiment, the firing is performed at 900°C or higher and 1050°C or lower. In this manner, by including a plurality of resin particles in the voltage nonlinearity characteristic ceramic slurry or ceramic paste, it becomes easier to form a structure in which the polycrystalline bodies C of the functional part 11 are connected to each other and contact the voids. As a result, the suppression voltage can be reduced.

[0085] In addition, by using resin particles, the opening surface of the gap is formed by dispersing the resin particles on the main surface of the internal electrode in the gap region. Therefore, it is possible to reduce the concentration of current density in the internal electrode due to ESD, and to suppress the burnout and wear of the internal electrode due to discharge, thereby lowering the suppression voltage. The volume ratio of the resin particles contained in the voltage nonlinearity characteristic ceramic slurry or ceramic paste to the total volume of the ceramic powder and the resin particles is set to 70%. The volume ratio of the resin particles is preferably 10% or more and 80% or less, thereby making it possible to significantly lower the suppression voltage. In addition, the average particle diameter of the resin particles is set to 1.8 μm, and the average particle diameter of the voltage nonlinearity characteristic ceramic powder is set to 1.1 μm. The average particle diameter of the resin particles is preferably larger than the average particle diameter of the ceramic powder. This makes it easier to form a structure in which the polycrystalline bodies C of the functional part 11 are connected to each other and contact the gap, making it possible to lower the suppression voltage. In addition, the average particle diameter of the resin particles is preferably equal to or smaller than the thickness of the functional part 11.

[0086] In this embodiment, the thickness of the functional part 11 is about 12 μm. After the ceramic green body and the conductive base that will become the internal electrode are brought into contact with each other to be integrally formed, the organic binder and the resin particles are removed to form the functional part 11 with a porosity of about 85%. In this way, when ESD is applied between the internal electrodes, a surface discharge can be generated on the surface of the polycrystalline body C that is in contact with the voids provided in the functional part 11. This can significantly reduce the suppression voltage.

[0087] Next, a paste containing conductive particles such as Ag, Cu, etc. is applied to both end faces of the compact, and then baked to form primary external electrodes. In this embodiment, Ag is used as the primary external electrodes. By using Ag-Pd for the internal electrodes and Ag for the primary external electrodes, good internal and external electrode connectivity can be achieved and internal stress can be alleviated. Furthermore, if it is desired to obtain the effect of alleviating stress during mounting and internal stress due to thermal shock during operation, a thermosetting conductive paste may be applied thereon to form secondary external electrodes. Also, in order to suppress oxidation, nitrogen gas or the like is introduced and the electrodes are heated in a low oxygen concentration (8.0×10 -1 The electrode may be baked at a temperature of 1000 ppm or less to further reduce the resistance. Next, a nickel layer and a tin layer may be successively formed on the surface of the electrode by electroplating. In this manner, the surge protection component 1 is obtained.

[0088] (summary) As is apparent from the above-described embodiment, the present disclosure includes the following aspects. In the following, reference symbols are given in parentheses only to clearly indicate the correspondence with the embodiment.

[0089] A surge protection component (1) of a first aspect includes an element body (10) and at least a pair of electrodes (31, 32). At least a portion of each of the pair of electrodes (31, 32) is disposed on the surface or inside the element body (10). The element body (10) includes a functional part (11) between the pair of electrodes (31, 32) that is made of a polycrystalline body (C) exhibiting voltage nonlinearity and has a gap. In at least one of the pair of electrodes (31, 32), a plurality of insulating particles (20) are present inside the electrode (31, 32) and at least one of the vicinity of the interface between the electrode (31, 32) and the functional part (11).

[0090] According to the first aspect, the surge protection component (1) can suppress deterioration of reliability while maintaining a good suppression effect by improving insulation when a rated voltage is applied, suppressing thermal runaway due to heat generation during operation, and suppressing wear of the electrodes (31, 32).

[0091] In the surge protection component (1) of the second embodiment, the pair of electrodes (31, 32) in the first embodiment are arranged inside the element body (10) as a pair of internal electrodes (31, 32) in which at least a part of each other's main surfaces face each other via the functional part (11). The element body (10) further includes an outer circumferential part (12) that covers the functional part (11) and has a smaller porosity than the functional part (11). The resistivity of the plurality of insulating particles (20) is higher than the resistivity of the polycrystalline body (C) of the functional part (11).

[0092] According to the second aspect, the surge protection component (1) can maintain its reliability by improving the insulation when the rated voltage is applied and by suppressing the decrease in resistance of the polycrystalline body (C) in the voids due to the suppression of thermal runaway caused by heat generation during operation, and can be suitably used as a surge absorption element.

[0093] In the surge protection component (1) of the third embodiment, in the second embodiment, each of the pair of internal electrodes (31, 32) has a first surface (S1) facing each other and a second surface (S2) opposite the first surface (S1) and not facing each other. The insulating particles (20) are unevenly distributed on the first surface (S1) side of the internal electrodes (31, 32).

[0094] According to the third aspect, in the surge protection component (1), the insulating particles (20) are interposed between the functional part (11) and the first surfaces (S1) of the first internal electrode (31) and the second internal electrode (32) which face each other, thereby improving the insulation property when the rated voltage is applied, and further suppressing thermal damage to the functional part (11) due to static electricity, and preventing a decrease in the insulation resistance of the surge protection component (1).

[0095] In the surge protection component (1) of the fourth embodiment, the insulating particles (20) of the third embodiment are not present on the second surface (S2) side of the internal electrodes (31, 32).

[0096] According to the fourth aspect, since the insulating particles (20) are not present on the second surface (S2) side, the bonding strength between the opposing first surfaces (S1) of the first internal electrode (31) and the second internal electrode (32) and the outer circumferential portion (12) is selectively improved, and breakage of the surge protection component (1) from the functional portion (11) due to internal stress generated by heat generation when static electricity is applied can be prevented.

[0097] In the surge protection component (1) of the fifth aspect, in the second aspect, each of the pair of internal electrodes (31, 32) has a first surface (S1) facing each other and a second surface (S2) opposite the first surface (S1) and not facing each other. The insulating particles (20) are unevenly distributed on the second surface (S2) side of the internal electrodes (31, 32).

[0098] According to the fifth aspect, the bonding strength between the second surface (S2) side of the first internal electrode (31) and the second internal electrode (32) and the outer circumferential portion (12) can be increased by the anchor effect.

[0099] In the surge protection component (1) of the sixth embodiment, the insulating particles (20) of the fifth embodiment are not present on the first surface (S1) side of the internal electrodes (31, 32).

[0100] According to the sixth aspect, the bonding strength between the second surface (S2) side of the first internal electrode (31) and the second internal electrode (32) and the outer circumferential portion (12) can be further increased.

[0101] In the surge protection component (1) of the seventh aspect, in the second aspect, each of the pair of internal electrodes (31, 32) has an end portion at an end in a direction perpendicular to the direction in which the pair of internal electrodes (31, 32) face each other. The insulating particles (20) are unevenly distributed on the end portion side of the internal electrodes (31, 32).

[0102] According to the seventh aspect, it is possible to prevent the first internal electrode (31) and the second internal electrode (32) from diffusing to the outer circumferential portion (12). This effect also makes it possible to prevent a current path caused by a reduction in resistance between the first external electrode (41) and the second external electrode (42) and the first internal electrode (31) and the second internal electrode (32), and thus it is possible to further improve the reliability of the surge protection component (1).

[0103] In the surge protection component (1) of the eighth aspect, in any one of the second to seventh aspects, when viewed from the direction in which the pair of internal electrodes (31, 32) face each other, the multiple insulating particles (20) are unevenly distributed in the region where the pair of internal electrodes (31, 32) overlap.

[0104] According to the eighth aspect, in the surge protection component (1), the effective volume through which current flows is increased in the first internal electrode (31) and the second internal electrode (32) other than the region where the first internal electrode (31) and the second internal electrode (32) overlap each other, so that a higher suppression effect can be obtained, and a short-circuit prevention effect can also be obtained in the region where the first internal electrode (31) and the second internal electrode (32) overlap each other.

[0105] In the surge protection component (1) of the ninth aspect, in any one of the second to eighth aspects, when viewed from the direction in which the pair of internal electrodes (31, 32) face each other, the multiple insulating particles (20) are unevenly distributed outside the region where the pair of internal electrodes (31, 32) overlap each other.

[0106] According to the ninth aspect, when the first internal electrode (31) and the second internal electrode (32) are formed thick or a plurality of internal electrodes are formed, there is a possibility that structural defects will occur at the end face of the element body (10). In this case, the anchor effect improves the bonding strength between the first internal electrode (31) and the second internal electrode (32) and the outer circumferential portion (12), thereby preventing breakage of the surge protection component (1).

[0107] The surge protection component (1) of a tenth aspect is any one of the second to ninth aspects, further comprising a pair of external electrodes (41, 42) electrically connected to each of the pair of internal electrodes (31, 32) on the surface of the element body (10). The insulating particles (20) are unevenly distributed in the internal electrodes (31, 32) near the external electrodes (41, 42).

[0108] According to the tenth aspect, during plating of the first external electrode (41) and the second external electrode (42), a short circuit of the functional part (11) caused by infiltration of plating liquid from the end face of the element body (10) can be prevented, and the reliability of the surge protection component (1) can be further improved.

[0109] In the surge protection component (1) of the eleventh aspect, in the second to tenth aspects, the polycrystalline body (C) contains ZnO, and the outer circumferential portion (12) contains glass ceramics.

[0110] According to the eleventh aspect, the polycrystalline body (C) of the functional part (11) contains ZnO and the outer peripheral part (12) contains glass ceramics, whereby the work function of the outer peripheral part (12) can be made smaller than that of the polycrystalline body (C), enabling discharge at a low voltage and further improving the surge absorption effect of the surge protection component (1).

[0111] In the surge protection component (1) of the twelfth aspect, in any one of the first to eleventh aspects, the pair of electrodes (31, 32) are arranged such that their end faces face each other with the functional part (11) interposed therebetween.

[0112] According to the twelfth aspect, the surge protection component (1) can further suppress wear of the electrodes (31, 32), thereby maintaining its reliability, and can be suitably used as an ESD suppressor.

[0113] In the surge protection component (1) of the thirteenth aspect, in any one of the first to twelfth aspects, the melting point of the insulating particles (20) is higher than the melting point of the polycrystal (C) of the functional part (11) and the melting point of the metal contained in the electrodes (31, 32).

[0114] According to the thirteenth aspect, the melting point of the insulating particles (20) is set higher than the melting point of the polycrystal (C) and the melting point of the metal contained in the electrodes (31, 32), thereby improving durability against heat generated by application during operation, thereby improving the reliability of the surge protection component (1).

[0115] In the surge protection component (1) of the fourteenth aspect, in any one of the first to thirteenth aspects, the work function of the insulating particles (20) is smaller than the work function of the polycrystalline body (C).

[0116] According to the fourteenth aspect, by using the insulating particles (20) having a work function smaller than that of the polycrystalline body (C), discharge can be promoted, and the surge protection component (1) can be suitably used in cases where a high suppression effect is required.

[0117] In the surge protection component (1) of the fifteenth aspect, in any one of the first to thirteenth aspects, the work function of the insulating particles (20) is greater than the work function of the polycrystalline body (C).

[0118] According to the fifteenth aspect, it is possible to adjust the suppression voltage without changing the element design such as the thickness of the functional portion (11), and reliability can be maintained even when a high rated voltage is required.

[0119] In the surge protection component (1) of the sixteenth aspect, in any one of the first to fifteenth aspects, the thermal conductivity of the insulating particles (20) is greater than the thermal conductivity of the polycrystals (C).

[0120] According to the sixteenth aspect, by using insulating particles (20) having a thermal conductivity greater than that of the polycrystalline body (C), the discharge start voltage can be controlled, and the surge protection component (1) can be selected according to the operating voltage of the object to be protected.

[0121] In the surge protection component (1) of the seventeenth aspect, in any one of the first to fifteenth aspects, the thermal conductivity of the insulating particles (20) is smaller than the thermal conductivity of the polycrystals (C).

[0122] According to the seventeenth aspect, by using insulating particles (20) having a thermal conductivity smaller than that of the polycrystals (C), it is possible to suppress the occurrence of breakage of the surge protection component (1) caused by heat shock.

[0123] In the surge protection component (1) of the 18th aspect, in any one of the 1 to 17 aspects, the insulating particles (20) contain an oxide of at least one element selected from the group consisting of B, Al, Y, Nd, Sm, Dy, Ca, Sr, Ba, Co, and Mg, or an oxide, nitride, or carbide of at least one element selected from the group consisting of Al, Zr, Y, and Si, or a combination thereof.

[0124] According to the 18th aspect, the surge protection component (1) can further improve heat dissipation by including the insulating particles (20) containing such a highly heat dissipating substance, and can further reduce the suppression voltage by including such a substance with a low work function, thereby further improving the suppression effect and further suppressing deterioration of reliability. [Explanation of symbols]

[0125] 1 Surge protection components 10 Base 11 Functional section 12 Outer periphery 20 Insulating particles 31 First electrode (first internal electrode) 32 Second electrode (second internal electrode) S1 First surface S2 Second surface 41 First external electrode 42 Second external electrode

Claims

1. The device includes an element body and at least one pair of electrodes, At least a portion of each of the pair of electrodes is disposed on a surface or inside of the element body, the element body includes a functional portion between the pair of electrodes, the functional portion being made of a polycrystalline material exhibiting voltage nonlinearity and having a gap; In at least one of the pair of electrodes, a plurality of insulating particles are present at least either inside the electrode or in the vicinity of the interface between the electrode and the functional portion. Surge protection components.

2. the pair of electrodes are disposed inside the element body as a pair of internal electrodes in which at least parts of main surfaces face each other via the functional portion, the element body further includes an outer circumferential portion that covers the functional portion and has a smaller porosity than the functional portion, The resistivity of the insulating particles is greater than the resistivity of the polycrystalline body of the functional portion. The surge protection component according to claim 1.

3. Each of the pair of internal electrodes has a first surface facing each other and a second surface opposite to the first surface and not facing each other, The insulating particles are unevenly distributed on the first surface side of the internal electrode. The surge protection component according to claim 2.

4. the insulating particles are not present on the second surface side of the internal electrode; The surge protection component according to claim 3.

5. Each of the pair of internal electrodes has a first surface facing each other and a second surface opposite to the first surface and not facing each other, The insulating particles are unevenly distributed on the second surface side of the internal electrode. The surge protection component according to claim 2.

6. the insulating particles are not present on the first surface side of the internal electrode; The surge protection component according to claim 5.

7. Each of the pair of internal electrodes has an end portion at an end in a direction perpendicular to a direction in which the pair of internal electrodes face each other, the insulating particles are unevenly distributed on the end side of the internal electrode; The surge protection component according to claim 2.

8. When viewed from a direction in which the pair of internal electrodes face each other, the insulating particles are unevenly distributed in a region where the pair of internal electrodes overlap each other. The surge protection component according to claim 2.

9. When viewed from a direction in which the pair of internal electrodes face each other, the insulating particles are unevenly distributed outside a region where the pair of internal electrodes overlap each other. The surge protection component according to claim 2.

10. a pair of external electrodes electrically connected to the pair of internal electrodes on a surface of the element body, the insulating particles are unevenly distributed in the internal electrode in the vicinity of the external electrode; The surge protection component according to claim 2.

11. The polycrystalline body contains ZnO, and the outer periphery contains glass ceramics. The surge protection component according to claim 2.

12. The pair of electrodes are arranged such that end surfaces of the pair of electrodes face each other via the functional portion. The surge protection component according to claim 1.

13. the melting point of the insulating particles is higher than the melting point of the polycrystalline body of the functional portion and the melting point of the metal contained in the electrode; The surge protection component according to claim 1.

14. The work function of the insulating particles is smaller than the work function of the polycrystalline body. The surge protection component according to claim 1.

15. The work function of the insulating particles is greater than the work function of the polycrystalline body. The surge protection component according to claim 1.

16. The thermal conductivity of the insulating particles is greater than the thermal conductivity of the polycrystalline body. The surge protection component according to claim 1.

17. The thermal conductivity of the insulating particles is lower than the thermal conductivity of the polycrystalline body. The surge protection component according to claim 1.

18. The insulating particles include an oxide of at least one element selected from the group consisting of B, Al, Y, Nd, Sm, Dy, Ca, Sr, Ba, Co, and Mg, or an oxide, nitride, carbide, or a combination thereof of at least one element selected from the group consisting of Al, Zr, Y, and Si. The surge protection component according to claim 1.

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