Multilayer Varistor

Abstract

To provide a multilayer varistor capable of suppressing the occurrence of migration on the high resistance layer surface.SOLUTION: A multilayer varistor (1) includes: a sintered body (11); Internal electrode (12) provided inside the sintered body (11); a high resistance layer (13) containing Si element formed to cover at least part of the sintered body (11); and a silver-based external electrode (14) electrically connected to the internal electrode (12) formed to cover part of the high resistance layer (13). The ratio of the total mass of alkali metal elements and alkaline earth metal elements to the mass of Si element in the surface layer of the high resistance layer (13) is 0.6 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a multilayer varistor, and more particularly to a multilayer varistor including a sintered body, an internal electrode, a high-resistance layer, and an external electrode. [Background technology]

[0002] Varistors are used to protect various electronic equipment and devices from abnormal voltages caused by lightning surges, static electricity, etc., and to prevent malfunctions of electronic equipment and devices caused by noise generated in circuits.

[0003] Patent Document 1 discloses a varistor comprising a varistor element body, an internal electrode, and an external electrode, the external electrode having a fired electrode layer formed by applying a conductive paste containing an alkali metal to the surface of the varistor element body and firing it, and the varistor element body having a high resistance region formed by the alkali metal contained in the conductive paste diffusing into the varistor element body from the interface between the surface of the varistor element body and the fired electrode layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-26447 Summary of the Invention [Problem to be solved by the invention]

[0005] In the varistor of Patent Document 1, the resistance of the varistor element surface is increased by including a large amount of alkali metal, which is thought to suppress plating deposition on the high-resistance layer surface during plating. However, in such varistors, particularly in connection with the use of external electrodes whose main component is Ag, migration may occur on the high-resistance layer surface under conditions of applied voltage and humidity.

[0006] An object of the present disclosure is to provide a multilayer varistor capable of suppressing the occurrence of migration on the surface of a high-resistance layer. [Means for solving the problem]

[0007] A laminated varistor according to one embodiment of the present disclosure comprises a sintered body, an internal electrode provided inside the sintered body, a high-resistance layer containing Si element provided so as to cover at least a part of the sintered body, and an external electrode mainly composed of silver provided so as to cover a part of the high-resistance layer and electrically connected to the internal electrode, wherein the ratio of the total mass of alkali metal element and alkaline earth metal element to the mass of Si element in the surface layer of the high-resistance layer is 0.6 or less. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a multilayer varistor capable of suppressing the occurrence of migration on the surface of a high-resistance layer. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view of a multilayer varistor according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] (1) Overview A multilayer varistor according to an embodiment of the present disclosure will be described below with reference to the drawings. Note that Figure 1 described in the following embodiment is a schematic diagram, and the ratios of the sizes and thicknesses of the components in Figure 1 do not necessarily reflect the actual dimensional ratios.

[0011] As shown in Fig. 1, the multilayer varistor 1 of this embodiment comprises a sintered body 11, an internal electrode 12, a high-resistance layer 13, and an external electrode 14. The multilayer varistor 1 may also comprise a plated electrode 15, as shown in Fig. 1.

[0012] The multilayer varistor 1 is characterized in that the ratio of the total mass of alkali metal elements and alkaline earth metal elements to the mass of Si element in the surface layer of the high-resistance layer 13 ((total mass of alkali metal elements and alkaline earth metal elements) / mass of Si element, hereinafter also referred to as element mass ratio (X)) is 0.6 or less. In this specification, the "surface layer of the high-resistance layer" refers to an exposed area of ​​the high-resistance layer 13 of the multilayer varistor 1 that is not covered by other layers, etc., and whose depth from the surface of the high-resistance layer 13 is within the detection depth of an EPMA (Electron Probe Micro Analyzer). An EPMA is a measuring device that analyzes constituent elements from the wavelength and intensity of characteristic X-rays generated by irradiating an object to be measured with an electron beam, and its detection depth is usually in the range of 0.1 μm to 10 μm, preferably in the range of 0.5 μm to 2 μm, and more preferably 1 μm.

[0013] The inventors have found that the occurrence of migration on the surface of the multilayer varistor 1 can be suppressed by controlling the element mass ratio (X) in the surface layer of the high-resistance layer 13 formed on the surface of the sintered body 11 to a specific value or less. The reason why the multilayer varistor 1 having the above-mentioned configuration achieves the above-mentioned effect is not entirely clear, but can be inferred as follows, for example. Migration in the multilayer varistor 1 occurs via the elution, migration, and precipitation of Ag ions and the like from the external electrodes 14. However, since the alkali metal elements and alkaline earth metal elements in the high-resistance layer 13 exist as metal oxides and are prone to hygroscopicity, it is thought that this makes ionization of silver and the like more likely to occur, making migration more likely to occur. In contrast, in the multilayer varistor 1, it is thought that the occurrence of migration on the surface of the high-resistance layer can be suppressed by controlling the element mass ratio (X), which corresponds to the amount of alkali metal elements and alkaline earth metal elements present in the surface layer of the high-resistance layer 13 and is the mass ratio to Si element, which is considered to be a less hygroscopic portion, to a specific value or less.

[0014] (2) Details <Multilayer varistor> 1 is a cross-sectional view of a multilayer varistor 1 according to an embodiment of the present disclosure. The multilayer varistor 1 comprises a sintered body 11, an internal electrode 12, a high-resistance layer 13, an external electrode 14, and a plated electrode 15.

[0015] The sintered body 11 is made of a semiconductor ceramic component having non-linear resistance characteristics.

[0016] The external electrode 14 is provided so as to cover a portion of the high-resistance layer 13 and is electrically connected to the internal electrode 12. The multilayer varistor 1 is only required to be provided with at least one pair of external electrodes 14. Here, the pair of external electrodes 14 includes a first external electrode 14A provided on one end surface of the sintered body 11 and a second external electrode 14B provided on the other end surface of the sintered body 11. When a voltage is applied between the first external electrode 14A and the second external electrode 14B, one of the first external electrode 14A and the second external electrode 14B becomes a high-potential electrode, and the other of the first external electrode 14A and the second external electrode 14B becomes a low-potential electrode.

[0017] The internal electrodes 12 are provided inside the sintered body 11. It is sufficient that one or more internal electrodes 12 are electrically connected to each of the external electrodes 14. In the multilayer varistor 1 of FIG. 1, the number of internal electrodes 12 is two. That is, the internal electrodes 12 include a first internal electrode 12A and a second internal electrode 12B, and the first internal electrode 12A is electrically connected to the first external electrode 14A, and the second internal electrode 12B is electrically connected to the second external electrode 14B.

[0018] The plated electrodes 15 are provided so as to cover at least a portion of the external electrodes 14. Of the pair of external electrodes 14, the multilayer varistor 1 has a first plated electrode 15A provided so as to cover at least a portion of the first external electrode 14A, and a second plated electrode 15B provided so as to cover at least a portion of the second external electrode 14B.

[0019] At least one pair of external electrodes 14 is mounted on a printed wiring board on which an electric circuit is formed. The multilayer varistor 1 is connected, for example, to the input side of the electric circuit. When a voltage exceeding a predetermined threshold voltage is applied between the first external electrode 14A and the second external electrode 14B, the electric resistance between the first external electrode 14A and the second external electrode 14B suddenly decreases, allowing a current to flow through the varistor layer, thereby protecting the electric circuit downstream of the multilayer varistor 1.

[0020] [Sintered body] The semiconductor ceramic component having nonlinear resistance characteristics that constitutes the sintered body 11 is, for example, composed of ZnO as the main component and Bi2O3, Co2O3, MnO2, Sb2O3, Pr6O as the secondary components. 11 , CaCO3, Cr2O3, etc. The varistor layer constituting the sintered body 11 is formed, for example, by firing a ceramic sheet containing these components, in such a way that the main components such as ZnO are dissolved and sintered with some of the secondary components, and the remaining secondary components are precipitated at the grain boundaries.

[0021] More specifically, the sintered body 11 is produced by, for example, cutting a laminate of ceramic sheets containing the above-mentioned components perpendicularly to the lamination surface, and firing the resulting pieces.

[0022] [Internal electrode] The internal electrodes 12 are provided inside the sintered body 11. The internal electrodes 12 contain, for example, Ag, Pd, PdAg, PtAg, etc., and are usually formed by stacking ceramic sheets coated with an internal electrode paste and firing them.

[0023] [High resistance layer] The high-resistance layer 13 is provided so as to cover at least a part of the sintered body 11. The high-resistance layer 13 contains Si element. The value of the element mass ratio (X) in the surface layer of the high-resistance layer 13 can be controlled by appropriately selecting a method for forming the high-resistance layer 13, which will be described later.

[0024] Examples of alkali metal elements that can be contained in the high-resistance layer 13 include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs). Examples of alkaline earth metal elements that can be contained in the high-resistance layer 13 include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba).

[0025] Of these elements, Na, K, Mg, and Ca are elements that can be contained in the multilayer varistor 1 obtained by a normal manufacturing method. In other words, the value of "the total mass of Na, K, Mg, and Ca elements" can be used as an approximation of the value of "the total mass of alkali metal elements and alkaline earth metal elements."

[0026] The element mass ratio (X) in the surface layer of the high-resistance layer 13 is 0.6 or less. This makes it possible to suppress the occurrence of migration on the surface of the high-resistance layer 13. If the element mass ratio (X) is greater than this value, the high-resistance layer 13 becomes too hygroscopic, making it easier for silver and other elements to ionize, and making it impossible to suppress the occurrence of migration in the high-resistance layer 13. The element mass ratio (X) is preferably 0.4 or less, more preferably 0.2 or less, even more preferably 0.1 or less, and particularly preferably 0.01 or less. The element mass ratio (X) is preferably 0.001 or more. In this case, the resistivity of the high-resistance layer 13 can be increased, thereby further suppressing plating deposition on the high-resistance layer 13. The element mass ratio (X) is more preferably 0.002 or more, and even more preferably 0.004 or more. The element mass ratio (X) in the surface layer of the high-resistance layer 13 can be determined by measuring the amount of each of the Si element, alkali metal element, and alkaline earth metal element present in the surface layer of the high-resistance layer 13 using an EPMA, and calculating the mass ratio using the atomic weight of each element.

[0027] The high resistance layer 13 contains Si elements. The proportion of Si elements in the high resistance layer 13 is preferably 5 mass % or more, and more preferably 10 mass % or more.

[0028] The main component of the high-resistance layer 13 is preferably SiO2 or ZnSiO4. By using SiO2 or ZnSiO4, which have low hygroscopicity, as the main component of the high-resistance layer 13, it is possible to further suppress the occurrence of migration on the surface of the high-resistance layer 13. In this specification, the term "main component" refers to the component with the largest mass percentage, preferably 30 mass% or more, and more preferably 50 mass% or more.

[0029] When the main component of the high-resistance layer 13 is SiO2 or ZnSiO4, the proportion of SiO2 or ZnSiO4 in the high-resistance layer 13 is preferably 50 mass% or more, more preferably 70 mass% or more, and even more preferably 90 mass% or more. The proportion of SiO2 or ZnSiO4 in the high-resistance layer 13 may be 100 mass%, and is preferably 99.9 mass% or less.

[0030] Furthermore, the mass concentrations of the alkali metal elements and alkaline earth metal elements in the high-resistance layer 13 are preferably lower than the mass concentrations of the alkali metal elements and alkaline earth metal elements in the sintered body 11. That is, the mass concentrations of the alkali metal elements and alkaline earth metal elements are preferably lower in the high-resistance layer 13 than in the sintered body 11. In this case, the alkali metal elements and alkaline earth metal elements in the sintered body 11 can control electrical characteristics such as the varistor voltage and can also suppress the occurrence of migration on the surface of the high-resistance layer 13.

[0031] The average thickness of the high-resistance layer 13 is preferably 0.01 μm or more and 5 μm or less, more preferably 0.05 μm or more and 3 μm or less, and even more preferably 0.1 μm or more and 1 μm or less. The "average thickness" refers to the arithmetic mean value of the thickness of the high-resistance layer 13 measured at multiple points (for example, any 10 points) on the high-resistance layer 13.

[0032] [External electrode] The external electrode 14 is provided so as to cover a part of the high resistance layer 13. The external electrode 14 is also electrically connected to the internal electrode 12.

[0033] The external electrode 14 may have a single layer structure consisting of only a primary external electrode, or may have a multi-layer structure including a primary external electrode and a secondary external electrode provided so as to cover the primary external electrode.

[0034] The main component of the external electrode 14 is silver. The proportion of silver in the external electrode 14 is preferably 30% by mass or more, more preferably 60% by mass or more, and even more preferably 90% by mass or more. The proportion of silver in the external electrode 14 may be 100% by mass.

[0035] The external electrodes 14 contain a component containing silver, such as Ag, AgPd, or AgPt, and a glass component, such as Bi2O3, SiO2, or B2O5.

[0036] [Plating electrode] The plating electrodes 15 are provided so as to cover at least a portion of the external electrodes 14. The plating electrodes 15 include, for example, Ni electrodes provided so as to cover at least a portion of the external electrodes 14, and Sn electrodes provided so as to cover at least a portion of the Ni electrodes.

[0037] <Manufacturing method for multilayer varistors> The multilayer varistor 1 can be manufactured by, for example, a manufacturing method including the following first to third steps. First step: A sintered body containing a semiconductor ceramic component as a main component and having an internal electrode disposed therein is prepared. Second step: A high-resistance layer containing Si elements is formed so as to cover at least a part of the sintered body obtained after the first step. Third step: Apply an external electrode paste containing silver as its main component so as to cover part of the high resistance layer and come into contact with part of the internal electrode.

[0038] The production method may further include the following fourth step. Fourth step: A plating electrode is formed so as to cover at least a part of the external electrodes formed from the external electrode paste. Each step will be described below.

[0039] [1st step] In the first step, a sintered body 11 containing a semiconductor ceramic component as a main component and having an internal electrode 12 disposed therein is prepared.

[0040] The semiconductor ceramic component preferably contains ZnO.

[0041] The sintered body 11 can be produced by applying an internal electrode paste to ceramic sheets prepared using a slurry containing semiconductor ceramic components, laminating the ceramic sheets, pressing, cutting, and then removing the binder and firing. The slurry contains, for example, a semiconductor ceramic component such as ZnO as the main raw material, and auxiliary raw materials such as Bi2O3, Co2O3, MnO2, Sb2O3, and Pr6O. 11 , Co2O 3、 It can be prepared by mixing CaCO3, Cr2O3, etc. with a binder.

[0042] As the internal electrode paste, for example, Ag paste, Pd paste, Pt paste, PdAg paste, PtAg paste, etc. can be used.

[0043] The temperature for removing the binder is, for example, 300° C. to 500° C. The temperature for firing can be appropriately adjusted depending on the structure, composition, etc. of the sintered body 11 to be obtained, and is, for example, 800° C. to 1300° C.

[0044] [Second process] In the second step, a high resistance layer 13 containing Si elements is formed so as to cover at least a part of the sintered body 11 after the first step.

[0045] Methods for forming the high-resistance layer 13 containing Si element include, for example, (i) a method of applying a solution containing a precursor of the high-resistance layer 13 to the sintered body 11, and (ii) a method of reacting SiO2 with the sintered body 11 whose main component is ZnO.

[0046] In the method (i), for example, a solution containing a precursor of the high-resistance layer 13 is applied to the sintered body 11, followed by dehydration and curing, thereby forming a high-resistance layer 13 containing Si element on the surface of the sintered body 11. Examples of precursors of the high-resistance layer 13 include glass components having Si element in the main chain, such as polysilazane. By using a glass component having Si element in the main chain, such as polysilazane, as the precursor of the high-resistance layer 13, a continuous high-resistance layer 13 containing SiO2 as the main component can be formed. By using SiO2, which has low hygroscopicity, as the main component of the high-resistance layer 13, the occurrence of migration on the surface of the high-resistance layer 13 can be further suppressed. When a precursor containing a salt containing an alkali metal element or an alkaline earth metal element is used, the amount of the alkali metal element and alkaline earth metal element is adjusted so that the element mass ratio (X) in the surface layer of the high-resistance layer 13 to be formed falls within a predetermined range.

[0047] Examples of methods for applying the solution containing the precursor include spraying, dipping, printing, and the like.

[0048] In method (ii), the high-resistance layer 13 can be formed by reacting the sintered body 11, which is primarily composed of ZnO, with SiO2 to convert the region near the surface of the sintered body 11 into a high-resistance layer 13, which is primarily composed of Zn2SiO4. By using ZnSiO4, which has low hygroscopicity, as the primary component of the high-resistance layer 13, the occurrence of migration on the surface of the high-resistance layer 13 can be further suppressed. Specifically, this method can be performed by, for example, applying a powder or liquid containing SiO2 to the sintered body 11, which is primarily composed of ZnO, followed by heat treatment. When the sintered body 11 contains an alkali metal element or an alkaline earth metal element, the content of the alkali metal element and alkaline earth metal element is adjusted so that the element mass ratio (X) in the surface layer of the high-resistance layer 13 to be formed falls within a predetermined range.

[0049] [3rd step] In the third step, an external electrode paste containing silver as a main component is applied so as to cover a part of the high resistance layer 13 and come into contact with a part of the internal electrode 12 .

[0050] An external electrode paste containing silver as its main component can be prepared by mixing a silver component such as Ag powder, AgPd powder, or AgPt powder with a glass component containing Bi2O3, SiO2, or B2O5, and a solvent. Alternatively, an external electrode paste containing silver as its main component and a resin component can also be used. After applying the external electrode paste, baking at a temperature of 700°C or higher and 800°C or lower can promote alloying with the internal electrode 12, resulting in the formation of an external electrode 14 with improved adhesion.

[0051] [4th step] In the fourth step, the plating electrode 15 is formed so as to cover at least a part of the external electrode 14 formed from the external electrode paste. The plating electrode 15 can be formed, for example, by electroplating, in which Ni plating and Sn plating are carried out in this order. [Example]

[0052] Hereinafter, the present disclosure will be specifically described with reference to examples, but the present disclosure is not limited to only these examples.

[0053] <Manufacturing of multilayer varistors> The multilayer varistors of Examples 1 and 2 and Comparative Examples 1 and 2 were manufactured according to the following procedure.

[0054] [Preparation of sintered body] (Preparation of slurry) The main raw material is ZnO and the secondary raw material is Pr6O 11 , Co2O 3、 CaCO3, Cr2O3, etc. were mixed with a binder to prepare a slurry.

[0055] (Ceramic sheet fabrication) The prepared slurry was molded into a ceramic sheet having a predetermined thickness of 20 μm or more and 50 μm or less.

[0056] (Laminate production) The internal electrode paste was a Pd paste, and the internal electrode paste was printed in a predetermined shape on the ceramic sheet prepared above. The ceramic sheet on which the internal electrode paste was printed and the ceramic sheet on which the internal electrode paste was not printed were laminated to form a predetermined electrode structure. The resulting laminate was pressed to a predetermined thickness, and then cut to a length of 1.0 mm, a width of 0.5 mm, and a height of 0.5 mm to obtain individual pieces of the laminate.

[0057] (Production of sintered body) Each piece of the laminate was subjected to debindering at a temperature of 300° C. to 500° C., and then fired at a temperature of 800° C. to 1300° C. to prepare a sintered body.

[0058] [Formation of high resistance layer] Example 1 A coating liquid containing polysilazane was sprayed onto the prepared sintered body using a sprayer, and then the precursor attached to the sintered body was cured at a temperature of 400°C or higher and 600°C or lower, thereby forming a high-resistance layer.

[0059] Example 2 A sodium silicate aqueous solution with a mass ratio of Si element to Na element of 2:1 was sprayed as a coating liquid using a sprayer, and a high resistance layer of ZnSiO4 was formed by heat treatment at 700°C or more and 900°C or less.

[0060] (Comparative Example 1) Sodium carbonate, potassium carbonate, magnesium carbonate, and calcium carbonate were deposited on the sintered body using a sealed rotary pot. The deposited material was then heat-treated in an electric furnace at 650°C to 900°C in air to diffuse the alkali metal and alkaline earth metal elements, forming a high-resistivity layer.

[0061] (Comparative Example 2) A high resistance layer was formed in the same manner as in Comparative Example 1, except that the composition ratio of sodium carbonate, potassium carbonate, magnesium carbonate, and calcium carbonate as the substances to be attached to the sintered compact was changed.

[0062] [Formation of external electrodes] The external electrode paste was prepared by mixing Ag powder, glass frit, and a solvent. This external electrode paste was applied to the end faces of the sintered body on which the high-resistance layer was formed, and then baked at 800°C to form the external electrodes.

[0063] [Formation of plating electrodes] On the external electrodes formed above, Ni-plated electrodes of a predetermined thickness were formed by electrolytic plating, and Sn-plated electrodes were formed thereon.

[0064] <Evaluation> [Measurement of element mass ratio] For the laminated varistors thus produced, the amounts of Si, K, Na, Mg and Ca present in the surface layer of the high-resistance layer were measured by EPMA using the measurement method shown below, and the element mass ratios of K / Si, Na / Si, Mg / Si and Ca / Si were calculated, as shown in Table 1, and the element mass ratio of (K+Na+Mg+Ca) / Si was determined. (Measurement method) Measurement equipment: JEOL electron probe microanalyzer (JXA-8100-EPMA) Measurement conditions: Acceleration voltage: 15 kV, probe current: 50 nA, measurement time: 10 sec, beam size: 200 μm 2 Analytical X-ray and spectroscopic crystal: Na Kα (1.191 nm) and TAPH (rubidium acid phthalate)

[0065] [Migration occurrence evaluation] The produced laminated varistors were subjected to a humidity load test under the following conditions to evaluate the occurrence of migration. (conditions) Temperature: 85°C, Relative humidity: 85%RH, Load voltage: 18V, Test time: 1000h (Migration evaluation) After the humidity and ambient load test, the appearance was observed to see if silver had deposited on the surface of the high-resistivity layer, i.e., whether migration had occurred.

[0066] [Table 1]

[0067] The results in Table 1 show that the element mass ratios (K+Na+Mg+Ca) / Si of the multilayer varistors of Examples 1 and 2 were 0.004 and 0.552, respectively, which are within the range of the present disclosure, and migration was suppressed. Also, the element mass ratios (K+Na+Mg+Ca) / Si of the multilayer varistors of Comparative Examples 1 and 2 were 0.996 and 0.701, respectively, which are outside the range of the present disclosure, and migration occurred.

[0068] (summary) As is clear from the above-described embodiments and examples, the multilayer varistor (1) of the first aspect comprises a sintered body (11), an internal electrode (12) provided inside the sintered body (11), a high-resistance layer (13) containing Si element provided so as to cover at least a part of the sintered body (11), and an external electrode (14) mainly composed of silver provided so as to cover a part of the high-resistance layer (13) and electrically connected to the internal electrode (12). The ratio of the total mass of alkali metal elements and alkaline earth metal elements to the mass of Si element in the surface layer of the high-resistance layer (13) is 0.6 or less.

[0069] According to the first aspect, by setting the proportion of alkali metal elements and alkaline earth metal elements, which exist in the high-resistance layer (13) as metal oxides that are easily absorbed by moisture and which facilitate the ionization of silver and the like, to a specific value or less, it is possible to suppress the occurrence of migration on the surface of the high-resistance layer.

[0070] In the laminated varistor (1) of the second embodiment, in the first embodiment, the ratio of the total mass of alkali metal elements and alkaline earth metal elements to the mass of Si elements in the surface layer of the high resistance layer (13) is 0.001 or more.

[0071] According to the second aspect, the resistivity of the high-resistance layer (13) can be increased, and thus plating deposition on the high-resistance layer (13) can be further suppressed.

[0072] In the laminated varistor (1) of the third aspect, in the first or second aspect, the total mass of the alkali metal elements and alkaline earth metal elements is the total mass of Na elements, K elements, Mg elements and Ca elements.

[0073] According to the third aspect, in the laminated varistor (1) obtained by the normal manufacturing method, the elements that can be contained are Na, K, Mg, and Ca, and therefore the value of "the total mass of Na element, K element, Mg element, and Ca element" can be used as an approximation of the value of "the total mass of alkali metal element and alkaline earth metal element."

[0074] In the laminated varistor (1) of the fourth aspect, in any one of the first to third aspects, the main component of the high resistance layer (13) is SiO2.

[0075] According to the fourth aspect, by using SiO2, which has low hygroscopicity, as the main component, it is possible to further suppress the occurrence of migration on the surface of the high resistance layer (13).

[0076] In the laminated varistor (1) of the fifth aspect, in any one of the first to third aspects, the main component of the high resistance layer (13) is ZnSiO4.

[0077] According to the fifth aspect, by using ZnSiO4, which has low hygroscopicity, as the main component, it is possible to further suppress the occurrence of migration on the surface of the high resistance layer (13).

[0078] In the laminated varistor (1) of the sixth aspect, in any one of the first to fifth aspects, the mass concentrations of the alkali metal elements and alkaline earth metal elements in the high resistance layer (13) are smaller than the mass concentrations of the alkali metal elements and alkaline earth metal elements in the sintered body (11).

[0079] According to the sixth aspect, the alkali metal elements and alkaline earth metal elements in the sintered body (11) can control electrical characteristics such as the varistor voltage, and can also suppress the occurrence of migration on the surface of the high resistance layer (13). [Explanation of symbols]

[0080] 1 Multilayer varistor 11 Sintered body 12 Internal electrode 13 High resistance layer 14 External electrode 15 Plating electrode

Claims

1. a sintered body; an internal electrode provided inside the sintered body; a high-resistance layer containing Si element, the high-resistance layer being provided so as to cover at least a portion of the sintered body; an external electrode mainly composed of silver, which is provided so as to cover a part of the high-resistance layer and is electrically connected to the internal electrode; Equipped with a ratio of the total mass of alkali metal elements and alkaline earth metal elements to the mass of Si elements in the surface layer of the high-resistance layer is 0.6 or less; the mass concentrations of the alkali metal element and the alkaline earth metal element in the high-resistance layer are lower than the mass concentrations of the alkali metal element and the alkaline earth metal element in the sintered body; Multilayer varistor.

2. a ratio of the total mass of the alkali metal element and the alkaline earth metal element to the mass of the Si element in the surface layer of the high-resistance layer is 0.001 or more; The multilayer varistor according to claim 1 .

3. the total mass of the alkali metal element and the alkaline earth metal element is the total mass of Na element, K element, Mg element, and Ca element; 3. The multilayer varistor according to claim 1 or 2.

4. The main component of the high resistance layer is SiO ２ That is, The multilayer varistor according to any one of claims 1 to 3.

5. The main component of the high resistance layer is ZnSiO ４ That is, The multilayer varistor according to any one of claims 1 to 3.

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