Barista, its manufacturing method, and its sorting method

Abstract

To provide a varistor that can improve electrical characteristics. [Solution] The varistor 1 comprises a ceramic body 11 containing zinc oxide and an oxide of at least one element selected from bismuth, praseodymium, and strontium, an internal electrode 12 disposed inside the ceramic body 11, and an insulating layer 13 disposed to cover the ceramic body 11. * a * b * In the color system, the chromaticity b of the surface S of the insulating layer 13 * However, b * >0

Description

Technical Field

[0001] The present disclosure relates to varistors, a method for manufacturing varistors, and a method for selecting varistors. More specifically, it relates to varistors provided with an insulating layer, a method for manufacturing such varistors, and a method for selecting such varistors.

Background Art

[0002] When an abnormal voltage such as a surge or static electricity is applied to a semiconductor integrated circuit or the like in an electronic device, the electronic device may malfunction or be damaged. A varistor is used as an electronic component to protect an electronic device from such an abnormal voltage. For varistors, it is required to improve electrical characteristics such as characteristics such as voltage non-linearity and leakage current characteristics, and resistances such as moisture resistance and ESD (Electro-Static Discharge) resistance with respect to these characteristics.

[0003] Patent Document 1 discloses a varistor. This varistor includes a sintered body of a voltage non-linear resistor composition having a plurality of zinc oxide particles and an oxide layer provided between the plurality of zinc oxide particles and containing at least one element selected from the group consisting of bismuth element, praseodymium element, and strontium element. And the color difference b* in the L*a*b* color system of the voltage non-linear resistor composition of the sintered body satisfies the range of 0 < b* ≤ 0.95. According to the technique of Patent Document 1, it is possible to measure the color difference of zinc oxide of the varistor and evaluate the resistance of the zinc oxide varistor from the obtained color difference, and thereby it is said that a varistor having good resistance can be stably obtained.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Some varistors have a structure with an insulating layer such as a glass coat layer for the purpose of improving insulation, enhancing mechanical strength, suppressing plating deposition during manufacturing, etc. However, with the technology of Patent Document 1, the electrical characteristics of varistors with an insulating layer cannot be improved.

[0006] An object of the present disclosure is to provide a varistor, a method for manufacturing a varistor, and a method for selecting a varistor that can improve electrical characteristics.

Means for Solving the Problems

[0007] A varistor according to an aspect of the present disclosure includes a ceramic body containing zinc oxide and an oxide of at least one element selected from the group consisting of bismuth element, praseodymium element, and strontium element, an internal electrode disposed inside the ceramic body, and an insulating layer disposed so as to cover the ceramic body. In the L * a * b * In the color system, the chromaticity b of the surface of the insulating layer * is * b > 0.

[0008] A method for manufacturing a varistor according to an aspect of the present disclosure includes a first step of obtaining a sintered body of a voltage non-linear resistor composition containing zinc oxide and an oxide of at least one element selected from the group consisting of bismuth element, praseodymium element, and strontium element, a second step of forming an internal electrode inside the sintered body after the first step, a third step of forming an insulating layer so as to cover the sintered body after the second step, and the L of the surface of the insulating layer of the sintered body after the third step * a * b * Measuring the chromaticity b in the color system * A fourth step, and a fifth step of selecting the sintered body in which the chromaticity b * is b * > 0.

[0009] A method for sorting a varistor according to one aspect of the present disclosure is a method for sorting a varistor comprising a ceramic body, an internal electrode disposed inside the ceramic body, and an insulating layer disposed so as to cover the ceramic body, wherein the surface L of the insulating layer * a * b * chromaticity a in a color system * and chromaticity b * Based on the measured values, the varistors are sorted into good and defective products. [Effects of the Invention]

[0010] According to this disclosure, it is possible to provide a varistor with improved electrical characteristics. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic perspective view of a varistor according to an embodiment of this disclosure. [Figure 2] Figure 2 is a schematic cross-sectional view of a varistor according to an embodiment of the present disclosure along line XX in Figure 1. [Modes for carrying out the invention]

[0012] (1) Overview The following is an overview of Barista 1, with reference to the drawings. Note that the drawings are schematic, and the size and thickness ratios of each component shown may not necessarily reflect the actual dimensional ratios.

[0013] The inventors have found a correlation between the electrical properties and the surface chromaticity of the insulating layer in a varistor comprising a specific ceramic element and an insulating layer, and have completed this disclosure.

[0014] The varistor 1 of this embodiment comprises a ceramic body 11, an internal electrode 12 disposed inside the ceramic body 11, and an insulating layer 13 disposed to cover the ceramic body 11. The ceramic body 11 includes zinc oxide and an oxide of at least one element selected from bismuth, praseodymium, and strontium.

[0015] In the varistor 1 of this embodiment, L * a * b * In the color system, the chromaticity b of the surface S of the insulating layer 13 * However, b * >0

[0016] According to the varistor 1 of this embodiment, electrical characteristics can be improved. Electrical characteristics of the varistor 1 include, for example, voltage nonlinearity, leakage current characteristics, and resistance to moisture, ESD, etc. for these characteristics. The reason why the varistor 1 achieves the above effect by having the above configuration can be inferred, for example, as follows: When the ceramic body 11 contains zinc oxide and an oxide of at least one element selected from bismuth, praseodymium, and strontium, on the surface S of the insulating layer 13 formed to cover the ceramic body 11, L * a * b * In particular, chromaticity b in color systems * The value of is thought to be related to the surface state of the insulating layer 13. That is, the chromaticity b of the surface S of the insulating layer 13. * If the above-mentioned specific range is present, the surface condition of the insulating layer 13 is considered to be good, and the variation on the surface S of the insulating layer 13 is considered to be small. As a result, a decrease in the insulation resistance value of the surface S and penetration of the plating solution during manufacturing are suppressed, and as a result, the electrical characteristics of the varistor 1 can be improved.

[0017] The manufacturing method of the varistor 1 of this embodiment (hereinafter also referred to as manufacturing method (P)) comprises a first step, a second step, a third step, a fourth step, and a fifth step. In the first step, a sintered body (hereinafter also referred to as sintered body A) of a voltage nonlinear resistor composition (hereinafter also referred to as composition I) containing zinc oxide and an oxide of at least one element selected from bismuth, praseodymium, and strontium is obtained. In the second step, an internal electrode 12 is formed inside the sintered body A after the first step. In the third step, an insulating layer 13 is formed so as to cover the sintered body A after the second step. In the fourth step, the surface S of the insulating layer 13 of the sintered body A after the third step is formed * a * b * chromaticity b in a color system * Measure the chromaticity b. In the fifth step, measure the chromaticity b. * ga b * Select sintered body A where >0.

[0018] According to the manufacturing method (P), the chromaticity b of the surface S of the insulating layer 13 formed on the sintered body A of composition I * ga b * By selecting and using sintered body A with >0, a varistor 1 with improved electrical characteristics can be manufactured simply and reliably.

[0019] The sorting method for the varistor 1 of this embodiment (hereinafter also referred to as sorting method (Q)) is a sorting method for the varistor 1 comprising a ceramic body 11, an internal electrode 12 disposed inside the ceramic body 11, and an insulating layer 13 disposed to cover the ceramic body 11. In sorting method (Q), the L of the surface S of the insulating layer 13 * a * b * chromaticity a in a color system * and chromaticity b * Based on the measured values, Barista 1 is sorted into good and defective products.

[0020] According to the sorting method (Q), the L of the surface S of the insulating layer 13 * a * b * chromaticity a in a color system *and chromaticity b * By sorting varistor 1 into good and defective units based on the measured values, it is possible to easily obtain good varistor 1 units with improved electrical characteristics.

[0021] (2) Details <Barista> The details of Barista 1 will be explained with reference to Figures 1 and 2.

[0022] The varistor 1 comprises a ceramic body 11, an internal electrode 12, and an insulating layer 13, and typically includes an external electrode 14, and may further include a plated electrode (not shown).

[0023] The varistor 1 is provided with at least one pair of internal electrodes 12 and external electrodes 14. The varistor 1 in Figures 1 and 2 is provided with one pair of internal electrodes 12 and one pair of external electrodes 14. The pair of internal electrodes 12 includes, for example, a first internal electrode 12A and a second internal electrode 12B. The pair of external electrodes 14 includes, for example, a first external electrode 14A provided on one end face of the ceramic body 11 and a second external electrode 14B provided on the other end face of the ceramic body 11. 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. In the varistor 1, one of the first external electrode 14A and the second external electrode 14B is the high-potential electrode, and the other of the first external electrode 14A and the second external electrode 14B is the low-potential electrode.

[0024] [Ceramic body] In varistor 1, the ceramic body 11 is composed of a semiconductor ceramic component having nonlinear resistance characteristics, and this semiconductor ceramic component includes zinc oxide and an oxide of at least one element selected from bismuth, praseodymium, and strontium. That is, the ceramic body 11 usually contains zinc oxide such as ZnO as the main component, and bismuth element oxides such as Bi2O3, Pr2O3, and Pr6O as minor components. 11It contains at least one of the following: praseodymium element oxides such as , and strontium element oxides such as SrO, and may also contain other element oxides such as Co2O3, MnO2, Sb2O3, CaCO3, and Cr2O3. The ceramic body 11 is formed in the semiconductor ceramic component by solid solution sintering of the main component such as ZnO with some of the minor components, and the remaining minor components precipitate at the grain boundaries.

[0025] The shape of the ceramic body 11 is, for example, a rectangular parallelepiped. When the ceramic body 11 is a rectangular parallelepiped, the dimensions of each side of the ceramic body 11 are, for example, 0.6 to 1.6 mm, 0.3 to 0.8 mm, 0.3 to 0.8 mm, etc. The corners of the ceramic body 11 may be chamfered as appropriate, and the corners of the ceramic body 11 may be rounded.

[0026] [Internal electrode] The internal electrode 12 is located inside the ceramic body 11. The internal electrode 12 contains a metal such as Ag, Pd, PdAg, or PtAg. The ceramic body 11 having the internal electrode 12 inside is formed, for example, by laminating ceramic sheets coated with an internal electrode paste containing these metals and then firing them.

[0027] [Insulating layer] The insulating layer 13 is arranged to cover the ceramic body 11. The insulating layer 13 is provided to cover at least a portion of the surface of the ceramic body 11, but it is preferable that it is provided to cover the entire surface of the ceramic body 11.

[0028] The average thickness of the insulating layer 13 is, for example, 0.01 μm or more and 5.0 μm or less, and preferably 0.1 μm or more and 1.5 μm or less. "Average thickness" means the arithmetic mean of the thickness measured at multiple points (for example, any 10 points) of the insulating layer 13.

[0029] The surface S of the insulating layer 13 is L * a * b * It has a color that can be represented using a color system. *a * b * The term "color system" refers to the system established by the International Commission on Illumination (CIE) in 1976, and is also defined in JIS-Z-8781-4. * a * b * In color systems, color is represented by lightness L, which indicates the degree of brightness. * And, the chromaticity a that represents the color * and chromaticity b * It is expressed as follows: chromaticity a * The positive direction is red, and the negative direction is green. Chromaticity b * The positive direction is yellow, and the negative direction is blue. Chromaticity a * and chromaticity b * The larger the absolute value, the more vivid the above colors become.

[0030] In varistor 1, the chromaticity b of the surface S of the insulating layer 13. * is, b * It is important that it is >0. In this case, varistor 1 can improve its electrical properties. The chromaticity b of the surface S of the insulating layer 13. * However, b * If the value is ≤0, it is considered that the surface condition of the insulating layer 13 is not good, and the varistor cannot improve its electrical properties.

[0031] Furthermore, in Barista 1, as described above, chromaticity b * In addition to being within a specific range, the chromaticity a of the surface S of the insulating layer 13 * is, a * It is preferable that the value is <0. In this case, the varistor 1 can further improve its electrical characteristics.

[0032] In Barista 1, as described above, chromaticity a * and chromaticity b * In addition to being within a specific range, the chromaticity a of the surface S of the insulating layer 13 * and chromaticity b * However, it is more preferable that the following equation (1) is satisfied. In this case, the electrical characteristics of varistor 1 can be further improved. b * <-5.0 × a *-5.0 ···(1)

[0033] Furthermore, in Barista 1, as described above, chromaticity a * and chromaticity b * In addition to being within a specific range, the chromaticity a of the surface S of the insulating layer 13 * However, -5.0 * It is even more preferable that the value be <-2.0. In this case, the electrical characteristics of varistor 1 can be further improved.

[0034] The method for forming the insulating layer 13 is not particularly limited, but it is preferable to form the insulating layer 13 by atomic layer deposition (ALD). By forming the insulating layer 13 by ALD, the surface condition of the insulating layer 13 can be improved, thereby further improving the electrical characteristics of the varistor 1.

[0035] ALD is a method for forming layers consisting of atomic layer deposits by introducing a gaseous precursor to the surface on which the layers are to be formed, and then irradiating it with O2 plasma, Ar plasma, or an oxidizing gas, and repeating these steps.

[0036] When forming an SiO2 layer as an insulating layer 13, for example, first, a precursor such as SiH[N(CH3)2]3, tetra(1-methoxy-2-methyl-2-propoxy)silane (Si(MMP)4), tetraethoxysilane (Si(OEt)4), or tetraisocyanatosilane (Si(NCO)4) is introduced onto the surface of the ceramic substrate 11, followed by purging. Next, a humidified Ar gas is introduced as an oxidizing gas, followed by purging, thereby forming a Si-containing layer. By repeating this formation of the Si-containing layer until a desired thickness of 0.1 μm to 2.0 μm is achieved, an SiO2 layer (single layer) can be formed.

[0037] ​When forming an Al2O3 layer as the insulating layer 13, an Al2O3 layer (single layer) can be formed by using Al(CH3)3 or the like as a precursor and humidified Ar gas or the like as an oxidizing gas.

[0038] Furthermore, by repeatedly forming the Al2O3 layer and the SiO2 layer as described above, a layer in which the Al2O3 layer and the SiO2 layer are stacked (Al2O3 / SiO2) can be formed. The number of each layer in this Al2O3 / SiO2 layer can be, for example, two or more, preferably three or more, more preferably four or more, and even more preferably five or more. In this case, the electrical characteristics of the varistor 1 can be further improved.

[0039] [External electrode] The external electrode 14 is provided so as to cover at least a portion of the insulating layer 13 and is electrically connected to the internal electrode 12.

[0040] The external electrode 14 contains, for example, a metallic component such as Ag, AgPd, or AgPt, and a glass component such as Bi2O3, SiO2, or B2O3. The external electrode 14 is preferably mainly composed of metal, and more preferably mainly composed of Ag.

[0041] The external electrode 14 may have a single-layer structure (external electrode 14A and external electrode 14B) or a multilayer structure having multiple layers.

[0042] The external electrode 14 is typically formed by applying an external electrode paste to a portion of the surface of the insulating layer 13 and baking it.

[0043] [Plating electrodes] The plating electrode is provided so as to cover at least a portion of the external electrode 14. The plating electrode includes, for example, a Ni electrode provided so as to cover at least a portion of the external electrode 14, and a Sn electrode provided so as to cover at least a portion of the Ni electrode.

[0044] <How to manufacture a barista machine> The manufacturing method (P) for Barista 1 comprises a first step, a second step, a third step, a fourth step, and a fifth step. The manufacturing method (P) may further include a sixth step after the fifth step.

[0045] [Step 1] In the first step, a sintered body A of composition I is obtained, which comprises zinc oxide and an oxide of at least one element selected from bismuth, praseodymium, and strontium.

[0046] In the first step, specifically, a voltage nonlinear resistor composition I is prepared, which is a slurry containing zinc oxide and an oxide of at least one element selected from bismuth, praseodymium, and strontium, and which typically contains a binder. A sintered body A is formed by laminating, pressing, cutting, debinding, and firing ceramic sheets made using this composition I.

[0047] The temperature at which the binder is removed is, for example, between 300°C and 500°C. The firing temperature can be appropriately adjusted depending on the composition and structure of the resulting ceramic body 11, for example, between 800°C and 1300°C.

[0048] [Step 2] In the second step, an internal electrode 12 is formed inside the sintered body A after the first step.

[0049] In the second step, the formation of the internal electrode 12 is specifically carried out by applying an internal electrode paste to ceramic sheets in the first step, stacking these ceramic sheets, and firing them. As the internal electrode paste, for example, Ag paste, Pd paste, Pt paste, PdAg paste, PtAg paste, etc. can be used.

[0050] [Step 3] In the third step, an insulating layer 13 is formed to cover the sintered body A after the second step.

[0051] It is preferable to use the ALD method to form the insulating layer 13.

[0052] Examples of the insulating layer 13 include SiO2 (single layer), Al2O3 (single layer), Al2O3 / SiO2 (multiple layers of each), etc.

[0053] [Step 4] In the fourth step, the chromaticity b of the surface S of the insulating layer 13 of the sintered body A after the third step is measured. * a * b * The chromaticity b in the color system * is measured.

[0054] Specifically, in the fourth step, the chromaticity b of the surface S of the insulating layer 13 formed to cover the sintered body A in the third step is measured. * is measured.

[0055] L * a * b * The chromaticity a in the color system * and the chromaticity b * can be measured by a known spectroscopic colorimeter.

[0056] [Step 5] In the fifth step, the sintered body A in which the chromaticity b * is b * > 0 is selected.

[0057] Specifically, in the fifth step, in the measurement in the fourth step, the sintered body A in which the chromaticity b of the surface S of the insulating layer 13 * is b * > 0 is formed and selected as a good product.

[0058] [Step 6] In the sixth step, an external electrode 14 is formed on the sintered body A selected in the fifth step.

[0059] In the sixth step, specifically, on a part of the surface of the insulating layer 13 of the sintered body A having the insulating layer 13 selected as a non-defective product in the fifth step, an external electrode paste is applied so as to be connected to the internal electrode 12, and then baking is performed to form the external electrode 14. The external electrode paste can be prepared by mixing, for example, a metal component containing Ag powder, AgPd powder, AgPt powder, etc., a glass component containing Bi2O3, SiO2, B2O3, etc., and a solvent. Further, as the external electrode paste, those containing Ag as a main component and a resin component can also be used. Examples of the method for applying the external electrode paste include dipping, printing, etc. The baking temperature is, for example, 700°C or higher and 800°C or lower.

[0060] In the sixth step, after the formation of the external electrode 14, the formation of a plating electrode may be performed so as to cover at least a part of the surface of the external electrode 14. Examples of the method for forming the plating electrode include a method of performing Ni plating and Sn plating in sequence by an electrolytic plating method.

[0061] In the fifth step, chromaticity b * is b * >0, instead of selecting the sintered body A in which the insulating layer 13 is formed, the chromaticity a of the surface S of the insulating layer 13 * is a * <0, the chromaticity a * and the chromaticity b * satisfy the formula (1) (formula (1): b * <-5.0×a * -5.0), or the chromaticity a * is -5.0 < a * <-2.0 may be selected as non-defective products. In the sixth step, using the sintered body A having the insulating layer 13 selected as non-defective products in these fifth steps, the varistor 1 is formed.

[0062] As described above, by the manufacturing method (P), the varistor 1 with improved electrical characteristics can be manufactured simply and reliably.

[0063] <Varistor sorting method> The varistor selection method (Q) is a method for selecting a varistor comprising a ceramic body 11, an internal electrode 12 disposed inside the ceramic body 11, and an insulating layer 13 disposed to cover the ceramic body 11. In the selection method (Q), the surface S of the insulating layer 13 is L * a * b * chromaticity a in a color system * and chromaticity b * Based on the measured values, Barista 1 is sorted into good and defective products.

[0064] In the sorting method (Q), chromaticity a * and chromaticity b * For the measured values, for example, chromaticity b * ga b * Products with a color value > 0 are selected as good products. Also, the chromaticity a of the surface S of the insulating layer 13. * However, a * <0, chromaticity a * and chromaticity b * However, those that satisfy equation (1): b * <-5.0 × a * -5.0), chromaticity a * However, -5.0 * Items with a score of <-2.0 may be selected as good quality products.

[0065] In this way, good quality varistors 1 can be easily obtained by the selection method (Q). Furthermore, by measuring the chromaticity of the surface S of the insulating layer 13 using the selection method (Q), the quality of the electrical performance of the varistors 1 can be predicted. [Examples]

[0066] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited to the examples alone.

[0067] [Barista production] Varistors of Examples 1-4 and Comparative Example 1, having the "Insulating Layer Configuration" shown in Table 1 below, were manufactured. The number of layers (single layer, 2 layers each, 5 layers each) shown in the insulating layer configuration refers to the number of Al2O3 layers and the number of SiO2 layers.​ In Examples 1-4, the insulating layer was formed using the ALD method. In Comparative Example 1, a precursor solution containing an insulating layer precursor material (such as polysilazane) was applied to the surface of a ceramic substrate, and then heat-treated to dehydrate and harden it, thereby forming a coated layer that would serve as an insulating layer.

[0068] [evaluation] Regarding the varistors of Examples 1 to 4 and Comparative Example 1 manufactured above, the chromaticity of the surface of the insulating layer a * and chromaticity b * We measured the V after the pressure cooker bias test (PCBT) as an example of the electrical characteristics of the varistor. 1μA The polarity difference was measured.

[0069] (Color a of the surface of the insulating layer) * and chromaticity b * ) L on the surface of the insulating layer of the manufactured varistor * a * b * chromaticity a in a color system * and chromaticity b * The chromaticity a was measured using a spectrophotometer. * and chromaticity b * The measured values ​​are shown in Table 1 below.

[0070] (Electrical characteristics) The varistors of Examples 1-4 and Comparative Example 1 manufactured above were subjected to a pressure cooker bias test (PCBT) (121°C, 100%RH) for 48 hours, and then the V after PCBT was tested. 1μA The polarity difference was measured (n=20). The evaluation results are shown in Table 1 below.

[0071] [Table 1]

[0072] As can be seen from the results in Table 1, the varistor in the example has improved electrical characteristics compared to the varistor in the comparative example.

[0073] (summary) As is clear from the embodiments described above, this disclosure includes the following aspects. In the following, reference numerals are enclosed in parentheses solely to indicate their correspondence with the embodiments.

[0074] The varistor (1) of the first embodiment comprises a ceramic body (11), an internal electrode (12), and an insulating layer (13). The ceramic body (11) comprises zinc oxide and an oxide of at least one element selected from bismuth, praseodymium, and strontium. The internal electrode (12) is disposed inside the ceramic body (11). The insulating layer (13) is disposed to cover the ceramic body (11). * a * b * In the color system, the chromaticity b of the surface (S) of the insulating layer (13) * However, b * >0

[0075] According to the first embodiment, the varistor (1) can improve its electrical characteristics.

[0076] In the varistor (1) of the second embodiment, the chromaticity a of the surface (S) of the insulating layer (13) is as described in the first embodiment. * However, a * < 0

[0077] According to the second embodiment, the varistor (1) can further improve its electrical characteristics.

[0078] In the varistor (1) of the third embodiment, the chromaticity a of the surface (S) of the insulating layer (13) is as defined in the first or second embodiment. * and chromaticity b * However, it satisfies equation (1) below. b * <-5.0 × a * -5.0 ···(1)

[0079] According to the third embodiment, the varistor (1) can further improve its electrical characteristics.

[0080] In the varistor (1) of the fourth embodiment, in any one of the first to third embodiments, the chromaticity a of the surface (S) of the insulating layer (13) * However, -5.0 * <-2.0.

[0081] According to the fourth embodiment, the varistor (1) can further improve its electrical characteristics.

[0082] A fifth embodiment of the method for manufacturing a varistor (1) comprises a first step, a second step, a third step, a fourth step, and a fifth step. In the first step, a sintered body of a voltage nonlinear resistor composition containing zinc oxide and an oxide of at least one element selected from bismuth, praseodymium, and strontium is obtained. In the second step, an internal electrode (12) is formed inside the sintered body after the first step. In the third step, an insulating layer (13) is formed so as to cover the sintered body after the second step. In the fourth step, the surface (S) of the insulating layer (13) of the sintered body after the third step is formed. * a * b * chromaticity b in a color system * Measure the chromaticity b. In the fifth step, measure the chromaticity b. * ga b * Select sintered bodies where the result is >0.

[0083] According to the fifth embodiment, a varistor (1) with improved electrical characteristics can be manufactured simply and reliably.

[0084] In the sixth embodiment of the method for manufacturing a varistor (1), the fifth embodiment further comprises a sixth step after the fifth step, in which an external electrode (14) is formed on the sintered body selected in the fifth step.

[0085] According to the sixth embodiment, a varistor (1) with improved electrical characteristics can be manufactured simply and reliably.

[0086] ​The seventh aspect of the varistor (1) sorting method is a method for sorting a varistor (1) comprising a ceramic body (11), an internal electrode (12) disposed inside the ceramic body (11), and an insulating layer (13) disposed to cover the ceramic body (11). * a * b * chromaticity a in a color system * and chromaticity b * Based on the measured values, the baristas (1) are sorted into good and defective products.

[0087] According to the seventh embodiment, a good quality varistor (1) with improved electrical characteristics can be easily obtained. [Explanation of Symbols]

[0088] 1 Barista 11 Ceramic Body 12 Internal electrode 13 Insulating layer 14 External electrode S surface of the insulating layer

Claims

1. A ceramic body comprising zinc oxide and an oxide of at least one element selected from bismuth, praseodymium, and strontium, An internal electrode is disposed inside the ceramic body, An insulating layer disposed to cover the ceramic body and Equipped with, L ＊ a ＊ b ＊ In the color system, the chromaticity b of the surface of the insulating layer. ＊ However, b ＊ > 0 Barista.

2. The chromaticity a of the surface of the insulating layer ＊ However, a ＊ < 0 The varistor according to claim 1.

3. the chromaticity a of the surface of the insulating layer ＊ and the chromaticity b ＊ satisfy the following formula (1) The varistor according to claim 2. b ＊ <-5.0×a ＊ -5.0 ・・・(1)

4. The chromaticity a of the surface of the insulating layer ＊ However, -5.0 < a ＊ < -2.0 The varistor according to claim 3.

5. A first step to obtain a sintered body of a voltage nonlinear resistor composition comprising zinc oxide and an oxide of at least one element selected from bismuth, praseodymium, and strontium; A second step involves forming internal electrodes inside the sintered body after the first step, A third step involves forming an insulating layer so as to cover the sintered body after the second step, L of the surface of the insulating layer of the sintered body after the third step ＊ a ＊ b ＊ chromaticity b in a color system ＊ The fourth step is to measure, The aforementioned chromaticity b ＊ ga b ＊ A fifth step is to select the sintered body which is > 0. A method for manufacturing a barista equipped with a barista.

6. After the fifth step, a sixth step is performed in which an external electrode is formed on the sintered body selected in the fifth step. The method for manufacturing a varistor according to claim 5, further comprising:

7. A method for selecting a varistor comprising a ceramic body, an internal electrode disposed inside the ceramic body, and an insulating layer disposed to cover the ceramic body, L on the surface of the insulating layer ＊ a ＊ b ＊ chromaticity a in a color system ＊ and chromaticity b ＊ Based on the measured values, the varistors are sorted into good and defective products. How to select a barista.

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