Ceramic component

Abstract

To provide a ceramic component capable of improving the insulation properties.SOLUTION: A ceramic component 1 includes: a ceramic body 11; an internal electrode 12 placed in the ceramic body 11; an insulation layer 13 formed to cover the surface of the ceramic body 11; and an external electrode 14 that is formed to cover part of the insulation layer 13 and is electrically connected to the internal electrode 12. The insulation layer 13 has a first layer 13X that is in contact with the ceramic body 11 and a second layer 13Y that is formed on the opposite side of the ceramic body 11 of the first layer 13X.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to ceramic components, and more particularly to ceramic components having an insulating layer. [Background technology]

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

[0003] Patent Document 1 discloses a multilayer chip varistor that includes an external electrode and a laminate having a varistor layer and an internal electrode, and describes a method for improving ESD resistance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-080950 Summary of the Invention [Problem to be solved by the invention]

[0005] The multilayer chip varistor of Patent Document 1 does not have an insulating layer, but ceramic components such as varistors generally have an insulating layer provided to cover the surface of the ceramic body for the purpose of increasing the insulation between the internal and external electrodes in order to improve electrical characteristics such as reducing leakage current. If Al2O3, which has a higher electrical resistance, is used as the material for this insulating layer, the ceramic component will not be able to improve its insulation properties, and there will be the disadvantage that its varistor characteristics and other properties will deteriorate.

[0006] An object of the present disclosure is to provide a ceramic component that can improve insulation properties. [Means for solving the problem]

[0007] A ceramic component according to one embodiment of the present disclosure comprises a ceramic body, an internal electrode disposed inside the ceramic body, an insulating layer disposed so as to cover the surface of the ceramic body, and an external electrode disposed so as to cover a portion of the insulating layer and electrically connected to the internal electrode, wherein the insulating layer has a first layer in contact with the ceramic body and a second layer disposed on the opposite side of the first layer from the ceramic body. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a ceramic component that can improve insulation properties. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of the ceramic part of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] 1. Overview The ceramic part 1 will now be outlined with reference to the drawings. Note that the drawings are schematic diagrams, and the ratios of the sizes and thicknesses of the components in the drawings do not necessarily reflect the actual dimensional ratios.

[0011] As described above, when Al2O3, for example, is used as the material for the insulating layer of a ceramic component, high temperatures, such as during firing during production of the ceramic component, cause mutual diffusion of Al2O3, the main component of the insulating layer, and ZnO, the main component of the ceramic body, and reactions such as forming a solid solution occur, resulting in deterioration of both the insulating layer and the ceramic body. Thus, when a material that is highly reactive with the main component of the ceramic body is used as the material for the insulating layer, the ceramic component cannot improve its insulation properties, and its varistor characteristics, etc., are reduced.

[0012] 1, the ceramic component 1 of this embodiment includes a ceramic body 11, an internal electrode 12 provided inside the ceramic body 11, an insulating layer 13 provided so as to cover the surface of the ceramic body 11, and an external electrode 14 provided so as to cover part of the insulating layer 13 and electrically connected to the internal electrode 12. The insulating layer 13 has a first layer 13X in contact with the ceramic body 11 and a second layer 13Y provided on the side of the first layer 13X opposite the ceramic body 11.

[0013] The ceramic component 1 of this embodiment has two layers as the insulating layer 13: a first layer 13X in contact with the ceramic body 11 and a second layer 13Y on the external electrode 14 side. By using such a layer structure for the insulating layer 13, the ceramic component 1 can improve its insulation properties. This improvement in insulation properties is presumed to be due to, for example, the boundary between the two layers acting as a barrier layer, which increases the insulation resistance.

[0014] 2.Details <Ceramic parts> The ceramic component 1 of this embodiment includes a ceramic body 11, an internal electrode 12, an insulating layer 13, and an external electrode 14, and may further include a plated electrode. Examples of the ceramic component 1 of this embodiment include a varistor, a thermistor, and a ceramic capacitor. Below, an example will be described in which the ceramic component 1 of this embodiment is a varistor 1.

[0015] The varistor 1 is required to have at least one pair of internal electrodes 12 and at least one pair of external electrodes 14. The varistor 1 in FIG. 1 has six internal electrodes 12 (three pairs) and two external electrodes 14 (one pair). The internal electrodes 12 include, for example, three first internal electrodes 12A and three second internal electrodes 12B. The external electrodes 14 include, 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 is the low-potential electrode.

[0016] [Ceramic body] In the varistor 1, the ceramic body 11 is made of, for example, a semiconductor ceramic component having nonlinear resistance characteristics. The ceramic body 11 usually contains ZnO as the main component and Bi2O3, Co2O3, MnO2, Sb2O3, and Pr6O as secondary components. 11 , CaCO3, Cr2O3, etc. Ceramic body 11 is formed by sintering a main component such as ZnO with a part of the secondary component in the semiconductor ceramic component to form a solid solution, and precipitating the remaining secondary component at the grain boundaries.

[0017] [Internal electrode] The internal electrode 12 is provided 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 therein is formed by stacking and firing ceramic sheets coated with an internal electrode paste containing such a metal, for example.

[0018] [Insulating layer] The insulating layer 13 is provided so as to cover the surface of the ceramic body 11. The insulating layer 13 may be provided so as to cover a part of the ceramic body 11, or may be provided so as to cover the entire surface of the ceramic body 11.

[0019] The insulating layer 13 has a first layer 13X and a second layer 13Y. The first layer 13X is a layer in contact with the ceramic body 11. The second layer 13Y is a layer provided on the opposite side of the first layer 13X from the ceramic body 11.

[0020] The average thickness of each of the first layer 13X and the second layer 13Y is, for example, 1 nm or more and 1000 nm or less, and preferably 10 nm or more and 200 nm or less. The "average thickness" refers to the arithmetic mean value of thicknesses measured at multiple points (e.g., any 10 points) on the cross section of the ceramic component.

[0021] The average thickness of the second layer 13Y and the average thickness of the first layer 13X may be the same or different, and the average thickness of the second layer 13Y may be greater than the average thickness of the first layer 13X. When the thickness of the second layer 13Y is greater than that of the first layer 13X, the mechanical strength of the ceramic component 1 can be further improved.

[0022] Examples of materials that form the first layer 13X and the second layer 13Y include SiO2, Al2O3, and ZrO2.

[0023] It is preferable that the composition of the first layer 13X is different from the composition of the second layer 13Y. By using first layer 13X and second layer 13Y with different compositions, it is possible to further improve the insulating properties. "Composition" refers to the types of materials constituting each layer and their content ratios (mass %). "Different compositions" between layers means that 95% or more by mass of the materials constituting the first layer 13X and the materials constituting the second layer 13Y are different materials.

[0024] The thermal conductivity of the first layer 13X is preferably greater than that of the second layer 13Y. By making the thermal conductivity of the first layer 13X greater than that of the second layer 13Y, the insulating properties of the second layer 13Y, which is the layer on the surface side of the insulating layer 13, can be made greater than those of the first layer 13X, which is the layer on the opposite side from the surface. With this arrangement, the insulating properties of the ceramic component 1 can be further improved.

[0025] It is preferable that the reactivity between the main component of the ceramic body 11 and the main component of the first layer 13X is lower than the reactivity between the main component of the ceramic body 11 and the main component of the second layer 13Y. In this case, it is possible to improve the insulation while maintaining the properties of both the ceramic body 11 and the insulating layer 13. "Reactivity" refers to the ease of interdiffusion and solution formation of the main components between layers, and specifically refers to the reactivity at temperatures (approximately 600°C to 1100°C) during firing after coating in forming the insulating layer 13 of the ceramic component 1, for example.

[0026] In other words, even if the material of the insulating layer 13 is, for example, a material that is highly reactive with the ceramic body 11, by using this material for the second layer 13Y, and by using a material that is low in reactivity with both the second layer 13Y and the ceramic body 11 for the material of the first layer 13X that contacts the ceramic body 11, it is possible to improve the insulation of the insulating layer 13 of the ceramic component 1 while maintaining the characteristics of both the ceramic body 11 and the insulating layer 13.

[0027] A preferred combination of materials for the first layer 13X and the second layer 13Y is that the first layer 13X contains SiO2 and the second layer 13Y contains Al2O3, which can provide excellent insulation while maintaining properties such as varistor characteristics.

[0028] Insulating layer 13 may further include a third layer (hereinafter also referred to as third layer 13Z) provided on the side of second layer 13Y opposite first layer 13X, or a fourth layer (hereinafter also referred to as fourth layer 13W) provided on the side of third layer 13Z opposite second layer 13Y. In these cases, the insulating properties can be further improved by increasing the number of barrier layers at the layer boundaries, etc.

[0029] It is preferable that the first to fourth layers 13X to 13W have the same layer structure repeatedly. That is, it is preferable that the first layer 13X and the third layer 13Z have the same composition, and the second layer 13Y and the fourth layer 13W have the same composition. In this case, the insulating properties can be further improved.

[0030] Furthermore, the insulating layer 13 may include, in addition to the first layer 13X to the fourth layer 13W, layers from the fifth layer onwards up to an nth layer (n is an integer of 5 or more). In these cases, the insulating properties can be further improved. n is preferably 7 or more, and more preferably 9 or more. The upper limit of n is, for example, 100 or less.

[0031] The average thickness of the insulating layer 13, that is, the total average thickness of the first layer 13X to the nth layer, is, for example, 10 nm or more and 1000 nm or less, and preferably 100 nm or more and 300 nm or less.

[0032] Each layer constituting the insulating layer 13 is preferably formed using atomic layer deposition (ALD). When forming an insulating layer using conventional methods such as PVD or CVD, it is difficult to form a uniform coating film like that formed by ALD. As a result, for example, the first layer may have many thin or uncoated areas, which may cause the second layer to come into contact with the ceramic body and react, resulting in deterioration of the varistor characteristics, etc. Each layer with a different composition can be formed by changing the precursor, etc., in ALD. By using ALD, a uniform insulating layer 13 can be easily and reliably formed even when the thickness of the layers to be formed is small and the number of layers is large. The insulating layer 13 is usually formed by firing a layer formed by ALD or the like at a temperature of approximately 600°C to 1100°C.

[0033] [External electrode] The external electrode 14 is provided so as to cover at least a part of the insulating layer 13 and is electrically connected to the internal electrode 12 .

[0034] The external electrodes 14 contain metal components such as Ag, AgPd, AgPt, etc., and glass components such as Bi2O3, SiO2, B2O3, etc. The external electrodes 14 preferably contain a metal as their main component, and more preferably contain Ag as their main component.

[0035] The external electrode 14 may have a single layer structure (external electrode 14A and external electrode 14B) or a multilayer structure having multiple layers.

[0036] The external electrodes 14 are usually formed by applying an external electrode paste containing the above-mentioned metal components to a portion of the surface of the insulating layer 13 and baking it.

[0037] [Plating electrode] The plating electrodes are provided so as to cover at least a portion of the external electrodes 14. The plating electrodes 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.

[0038] It is believed that the ceramic component 1 of this embodiment, such as a thermistor or ceramic capacitor other than the varistor 1, can also have improved insulation properties.

[0039] <Method of manufacturing ceramic parts> The method for manufacturing a ceramic component according to this embodiment includes steps 1, 2, and 3. The method for manufacturing a ceramic component may further include a fourth step of forming a plating electrode.

[0040] [1st step] In the first step, a ceramic body 11 having an internal electrode 12 therein is formed.

[0041] In the first step, an internal electrode paste is applied to ceramic sheets made using a slurry containing, for example, ZnO, and the ceramic sheets are then laminated, pressed, cut, and then debindered and fired to produce a ceramic body 11 having an internal electrode 12 therein. The slurry may contain, for example, ZnO as the main raw material and Bi2O3, Co2O3, MnO2, Sb2O3, and Pr6O as auxiliary raw materials. 11 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 firing temperature can be adjusted appropriately depending on the structure, composition, etc. of the ceramic body 11 to be obtained, and is, for example, 800° C. to 1300° C.

[0044] [Second process] In the second step, multiple layers are laminated on the surface of the ceramic body 11 as the insulating layer 13. That is, in the second step, multiple layers, from the first layer to the nth layer, are formed in order on the surface of the ceramic body 11. In the second step, typically, after the multiple layers are formed, a coating and firing process is performed. In this manner, the insulating layer 13 can be formed. Alternatively, instead of performing the coating and firing process in the second step, the external electrodes may be fired in the third step, thereby forming the insulating layer 13.

[0045] The method for forming each layer in the second step may be, for example, a method using atomic layer deposition (ALD).

[0046] In ALD, a gaseous precursor is introduced to the ceramic body 11 or the surface on which a layer such as an SiO2 layer is to be formed, and O2 plasma, Ar plasma, etc. are irradiated. These processes are repeated to form layers made of atomic layer deposition. Layers with different compositions can also be formed by changing the type of precursor and repeating the above process.

[0047] As a precursor, for example, bis(ethylmethylamino)silane (BEMAS) or the like is used to form SiO2, and trimethylaluminum or the like is used to form Al2O3. In addition, O2 plasma irradiation is performed to form SiO2 and Al2O3.

[0048] The temperature for baking after coating is usually about 600°C to 900°C, and preferably 700°C or higher and 800°C or lower.

[0049] [3rd step] In the third step, the external electrodes 14 are formed on parts of the surface of the insulating layer 13 .

[0050] In the third step, an external electrode paste is applied to, for example, a portion of the surface of the insulating layer 13 so as to contact a portion of the internal electrode 12, and then baked to form the external electrode 14. The external electrode paste can be prepared by mixing a metal component containing, for example, Ag powder, AgPd powder, AgPt powder, etc., a glass component containing, for example, Bi2O3, SiO2, B2O3, etc., and a solvent. Alternatively, an external electrode paste containing Ag as the main component and a resin component can also be used. Examples of methods for applying the external electrode paste include dipping and printing. The baking temperature is, for example, 700°C or higher and 800°C or lower.

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

[0052] The present disclosure will be specifically described below using examples, but the present disclosure is not limited to these examples.

[0053] <Ceramic parts manufacturing> The ceramic parts of Comparative Example 1 and Examples 1 and 2 were manufactured by forming an SiO layer and an AlO layer on the surface of a ceramic body containing ZnO as the main component using atomic layer deposition (ALD) to have the layer structure shown below, or by repeating this formation. [Comparative Example 1] Al2O3 single layer (average layer thickness: 200 μm) [Example 1] First layer: SiO2, second layer: Al2O3 (average thickness of each layer: 100 μm) [Example 2] 1st, 3rd, 5th, 7th, and 9th layers: SiO2; 2nd, 4th, 6th, 8th, and 10th layers: Al2O3 (average thickness of each layer: 20 μm)

[0054] The SiO2 layer and Al2O3 layer were formed by ALD as follows. SiO2 layer: Bis(ethylmethylamino)silane (BEMAS) was introduced as a precursor to form a Si-containing layer, followed by purging. Next, the Si-containing layer was irradiated with O2 plasma to form a SiO2 layer. Al2O3 layer: Trimethylaluminum was introduced as a precursor to form an Al-containing layer, followed by purging. Next, the Al-containing layer was irradiated with O2 plasma to form an Al2O3 layer.

[0055] The insulating properties of each of the ceramic parts manufactured as described above were evaluated by the following method.

[0056] <Evaluation> [Insulating] To evaluate insulation, the V after 48 hours of accelerated humidity testing using a pressure cooker bias test (PCBT) was performed on the ceramic components mounted on the board. 1μAThe polarity difference (V when voltage is applied in the positive and negative directions) 1μA The difference between V 1μA The smaller the polarity difference, the better the insulating properties.

[0057] Table 1 below shows the evaluation results of the insulating properties, together with the number of layers constituting the insulating layer and the layer configuration.

[0058] [Table 1]

[0059] As is clear from the results in Table 1, the ceramic parts of Examples 1 and 2 have improved insulating properties compared to the ceramic part of Comparative Example 1. Furthermore, as can be seen from a comparison between Example 2 and Example 1, the greater the number of layers constituting the insulating layer, the more the insulating properties are improved.

[0060] (summary) As is clear from the above embodiments, the present disclosure includes the following aspects. In the following, reference numerals are given in parentheses only to clarify the correspondence with the embodiments.

[0061] The ceramic component 1 of the first aspect includes a ceramic body 11, an internal electrode 12 provided inside the ceramic body 11, an insulating layer 13 provided so as to cover the surface of the ceramic body 11, and an external electrode 14 provided so as to cover a portion of the insulating layer 13 and electrically connected to the internal electrode 12. The insulating layer 13 has a first layer 13X in contact with the ceramic body 11 and a second layer 13Y provided on the side of the first layer 13X opposite the ceramic body 11.

[0062] According to the first aspect, the ceramic part (1) can have improved insulation properties.

[0063] In the ceramic part (1) of the second embodiment, the composition of the first layer (13X) is different from the composition of the second layer (13Y) in the first embodiment.

[0064] According to the second aspect, the ceramic part (1) can have improved insulation properties.

[0065] In the ceramic part (1) of the third aspect, in the first or second aspect, the reactivity between the main component of the ceramic body (11) and the main component of the first layer (13X) is lower than the reactivity between the main component of the ceramic body (11) and the main component of the second layer (13Y).

[0066] According to the third aspect, the ceramic part (1) can improve the insulating properties while maintaining the properties of both the ceramic body (11) and the insulating layer (13).

[0067] In the ceramic part (1) of the fourth aspect, in any one of the first to third aspects, the thermal conductivity of the first layer (13X) is greater than the thermal conductivity of the second layer (13Y).

[0068] According to the fourth aspect, the ceramic part (1) can have improved insulation properties.

[0069] In the ceramic part (1) of the fifth aspect, in any one of the first to fourth aspects, the ceramic body (11) contains ZnO as a main component, the first layer (13X) contains SiO2, and the second layer (13Y) contains Al2O3.

[0070] According to the fifth aspect, the ceramic part (1) can have excellent insulating properties while maintaining characteristics such as varistor characteristics.

[0071] In the ceramic part (1) of the sixth aspect, in any one of the first to fifth aspects, the average thickness of the second layer (13Y) is greater than the average thickness of the first layer (13X).

[0072] According to the sixth aspect, the ceramic part (1) can have improved mechanical strength and the like.

[0073] In the ceramic part (1) of the seventh aspect, in any one of the first to sixth aspects, the insulating layer (13) further has a third layer (13Z) provided on the side of the second layer (13Y) opposite to the first layer (13X).

[0074] According to the seventh aspect, the ceramic part (1) can have further improved insulation properties.

[0075] In the ceramic part (1) of the eighth aspect, the insulating layer (13) of the seventh aspect further includes a fourth layer (13W) provided on the opposite side of the third layer (13Z) from the second layer (13Y).

[0076] According to the eighth aspect, the insulating properties of the ceramic part (1) can be further improved. [Explanation of symbols]

[0077] 1. Ceramic parts (varistors) 11 Ceramic body 12 Internal electrode 13 Insulating layer 13X 1st layer 13Y 2nd layer 14 External electrode

Claims

1. A ceramic body; an internal electrode provided inside the ceramic body; an insulating layer provided to cover the surface of the ceramic body; an external electrode provided so as to cover a part of the insulating layer and electrically connected to the internal electrode; The insulating layer has a first layer in contact with the ceramic body and a second layer provided on the opposite side of the first layer from the ceramic body. Ceramic parts.

2. The composition of the first layer is different from the composition of the second layer. The ceramic part of claim 1 .

3. The reactivity between the main component of the ceramic body and the main component of the first layer is lower than the reactivity between the main component of the ceramic body and the main component of the second layer. The ceramic part of claim 1 .

4. The thermal conductivity of the first layer is greater than the thermal conductivity of the second layer. The ceramic part of claim 1 .

5. the ceramic body contains ZnO as a main component, The first layer is SiO ２ Including, The second layer is Al ２ O ３ Contains The ceramic part of claim 1 .

6. The average thickness of the second layer is greater than the average thickness of the first layer. The ceramic part of claim 1 .

7. The insulating layer further includes a third layer provided on the opposite side of the second layer from the first layer. The ceramic part of claim 1 .

8. The insulating layer further includes a fourth layer provided on the opposite side of the third layer from the second layer. The ceramic part of claim 7.

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