JP2012028689A - Terminal electrode and ceramic electronic component equipped with it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a terminal electrode for a ceramic electronic component exhibiting high adhesion to a ceramic element and having excellent conductivity and mechanical strength.SOLUTION: The terminal electrode 10 for a ceramic electronic component 100 provided on a ceramic element 20 consists of a first layer 4 containing nickel and a nickel oxide, and a second layer 5 containing copper and a copper oxide formed in this order from the ceramic element 20 side. The first layer 4 has porosity higher than that of the second layer 5.

Description

  The present invention relates to a terminal electrode and a ceramic electronic component including the terminal electrode.

  Ceramic electronic components such as varistors and capacitors include terminal electrodes formed by baking. As a material of such a terminal electrode, a base metal such as copper may be used because of cost advantages. Usually, since base metals are easily oxidized, when a terminal electrode is formed by baking a paste containing base metals in the atmosphere, the resistance value increases and good conductivity is impaired. For this reason, as a measure for suppressing oxidation of the base metal, a technique of coating the surface of the base metal particle with a noble metal or glass is known. As another measure, it is proposed that the terminal electrode is baked in a nitrogen atmosphere in which the oxygen concentration is sufficiently reduced (see, for example, Patent Document 1). In such a terminal electrode, a plating layer may be formed as the outermost layer.

  On the other hand, ceramic electronic parts such as inductors, semiconductors, and high-frequency parts are usually baked in the air because their characteristics deteriorate when baked in a reducing atmosphere. For this reason, noble metals such as silver and palladium which are not easily oxidized are used as the material of the terminal electrode. However, since precious metals are expensive, they hinder manufacturing cost reduction of ceramic electronic components.

JP 2005-222831 A

  Since the terminal electrode provided in the ceramic electronic component is connected not only to good conductivity but also to a substrate or the like, it is required to have durability against external force and impact. Further, ceramic electronic components are required to reduce the manufacturing cost, and it is required to reduce the amount of expensive noble metal used. However, in order to reduce the amount of noble metal used, it is difficult to prevent the occurrence of pinholes in the coat even if particles obtained by coating the surface of base metal particles with noble metal or glass are used. In addition, if the coating material starts to be softened when the terminal electrode is baked, the internal base metal is exposed to the outside air and oxidation proceeds at a stretch, and there is a concern that the conductivity of the terminal electrode is impaired. In addition, there is a concern that the mechanical strength of the terminal electrode and the adhesive force between the terminal electrode and the ceramic body are reduced. Under these circumstances, ceramic electronic components that have high mechanical strength against external forces and impacts and high adhesion to the ceramic body, even when formed by baking in an atmosphere containing oxygen using a base metal There is a need for terminal electrodes.

  The present invention has been made in view of the above circumstances, and provides a terminal electrode for a ceramic electronic component having high adhesive strength with a ceramic body, excellent electrical conductivity, and excellent mechanical strength. Objective. Moreover, it aims at providing the ceramic electronic component which has high reliability by providing such a terminal electrode.

  In the present invention, in the first aspect, a terminal electrode for a ceramic electronic component provided on the ceramic body, the first layer containing nickel and nickel oxide, and copper and oxide from the ceramic body side A second layer comprising copper, the first layer providing a terminal electrode having a higher porosity than the second layer.

  In the terminal electrode of the present invention, since the first layer has a higher porosity than the second layer, when a force is applied in a direction parallel to the interface between the ceramic body and the terminal electrode, The first layer can be slightly distorted to absorb the force. For this reason, the terminal electrode of this invention has the outstanding mechanical strength. Moreover, since the 1st layer arrange | positioned at the ceramic body side contains nickel oxide, the adhesive force with a ceramic body is high. Thus, since the terminal electrode of the present invention has a high porosity and includes the first layer containing nickel oxide, the terminal electrode has high adhesive strength with the ceramic element body and excellent mechanical strength.

  In addition, since the terminal electrode of the present invention includes the second layer that is denser than the first layer, when the plating layer is formed on the second layer, the plating solution is used for the ceramic body and the terminal electrode. It is possible to sufficiently suppress intrusion in the meantime. As a result, the corrosion of the ceramic body and the decrease in the adhesive strength between the ceramic body and the terminal electrode can be suppressed. Furthermore, since the second layer contains copper and copper oxide, surface activity can be suppressed as compared with a terminal electrode made of only copper while maintaining excellent conductivity. Thus, since surface activity is suppressed, even if it heats in post-processing, it is hard to be oxidized and it is hard to react. Therefore, the stability of the structure can be maintained well.

  In the terminal electrode of the present invention, the porosity of the first layer is preferably 5 to 30% by volume, and the porosity of the second layer is preferably less than 5% by volume. Thereby, it is possible to further increase the mechanical strength of the terminal electrode and further suppress the intrusion of the plating solution between the ceramic body and the terminal electrode.

  In the present invention, in a second aspect, a ceramic body and a ceramic electronic component including the above-described terminal electrode on the ceramic body are provided. Since the terminal electrode in the ceramic electronic component of the present invention has the above-described characteristics, it has high reliability.

  ADVANTAGE OF THE INVENTION According to this invention, the adhesive force with a ceramic element | base_body can be provided, and the terminal electrode for ceramic electronic components which has the outstanding electroconductivity and the outstanding mechanical strength can be provided. Moreover, since such a terminal electrode is provided, a highly reliable ceramic electronic component can be provided.

It is sectional drawing which shows typically one suitable embodiment of the ceramic electronic component of this invention.

  In the following, preferred embodiments of the present invention will be described with reference to the drawings as the case may be.

  FIG. 1 is a schematic cross-sectional view of the ceramic electronic component of the present embodiment. The ceramic electronic component of this embodiment is a varistor 100 including a varistor element body 20 and a terminal electrode 10 provided on a main surface 20a of the varistor element body 20. The terminal electrode 10 for the varistor 100 has a laminated structure in which the first layer 4 and the second layer 5 are laminated in this order from the varistor element body 20 side. The varistor element body 20 has a laminated structure in which varistor layers 22, 24, and 26 are laminated in this order. A via hole electrode 32 is formed in the via hole provided in each varistor layer 22, 24, 26. A via-hole electrode 32 provided on the varistor layer 22 disposed on the main surface 20 a side of the varistor element body 20 is in physical contact with the first layer 4. Therefore, the terminal electrode 10 is electrically connected to the internal electrode 34 embedded between the varistor layers 22, 24, and 26 via the via hole electrode 32.

  The terminal electrode 10 is a conductor and has a first layer 4 and a second layer 5 having different compositions and porosity from the varistor element body 20 side. The first layer contains nickel and nickel oxide as main components. The total content of nickel and nickel oxide in the first layer is preferably 50 to 95% by mass and more preferably 60 to 80% by mass in terms of nickel. If the total content of nickel and nickel oxide is too low, the sufficiently high adhesive force between the varistor element body 20 and the first layer 4 tends to be impaired. On the other hand, when the total content of nickel and nickel oxide becomes too high, the number of pores increases and the resistance value tends to increase.

  The thickness of the first layer 4 is preferably 5 to 20 μm, more preferably 10 to 15 μm from the viewpoint of sufficiently maintaining the function as the terminal electrode 10 and sufficiently excellent mechanical strength. .

  The second layer 5 contains copper and copper oxide as main components. The total content of copper and copper oxide in the first layer is preferably 50 to 95% by mass and more preferably 60 to 80% by mass in terms of copper. When the total content of copper and copper oxide becomes too low, the excellent conductivity of the terminal electrode 10 tends to be impaired. On the other hand, when the total content of copper and copper oxide becomes too high, oxidation proceeds, the resistance value increases, and the conductivity tends to be impaired.

  The total content of nickel and nickel oxide in the second layer 5 is preferably 20% by mass or less, and more preferably 10% by mass or less. If the total content of nickel and nickel oxide in the second layer 5 becomes too high, it becomes difficult to remove the oxide by etching when forming a plating layer on the second layer 5, and formation of the plating layer Tend to be difficult.

  The thickness of the second layer 5 is preferably 0.5 to 10 μm from the viewpoint of sufficiently maintaining the function as the terminal electrode 10 and sufficiently excellent in the mechanical strength of the terminal electrode 10. More preferably, it is 0.5-5 micrometers.

  In this specification, the porosity of each electrode layer (the first layer 4 and the second layer 5) can be determined by the following procedure. First, a ceramic electronic component is filled with resin and polished. The cross section of each electrode layer is observed using a scanning electron microscope (SEM, magnification: 1500 times) to identify the holes. The total area of the specified holes is divided by the total area of the observation image to calculate the area ratio of the holes. The calculated area ratio is converted into a volume ratio. In this way, the porosity of each electrode layer can be determined.

  In this specification, the composition of each electrode layer (the first layer 4 and the second layer 5) and the ceramic body can be determined as follows. First, in the same manner as when determining the porosity, the cross sections of each electrode layer and the ceramic body were observed using a scanning electron microscope (SEM, magnification: 2000 times). Confirm the area. Thereafter, the metal element is quantified by energy dispersive X-ray analysis (EDS). Thereby, the content of the metal element can be measured. Moreover, the presence or absence of an oxide can be confirmed by analyzing the presence or absence of oxygen.

  The porosity of the 1st layer 4 becomes like this. Preferably it is 5-30 volume%, More preferably, it is 5-15 volume%, More preferably, it is 5-10 volume%. Thus, since the first layer 4 has a higher porosity than the second layer 5, the terminal electrode 10 is formed when a force parallel to the main surface 20 a is applied to the terminal electrode 10. It is possible to sufficiently suppress peeling from the main surface 20a of the varistor element body 20 and damage to the terminal electrode 10 itself. For this reason, the terminal electrode 10 has excellent mechanical strength. Note that if the porosity of the first layer 4 becomes too high, the electrical resistance of the terminal electrode 10 tends to increase. On the other hand, if the porosity of the first layer 4 becomes too low, it may be difficult to obtain an effect of improving the mechanical strength.

  The porosity of the second layer 5 is preferably less than 10% by volume, more preferably less than 5% by volume, and even more preferably less than 3% by volume. Thus, since the second layer 5 has a lower porosity than the first layer 4, it is sufficiently dense. For this reason, when providing a plating layer on the 2nd layer 5, it can suppress that a plating solution penetrate | invades into the interface of the varistor element body 20 and the terminal electrode 10, or the inside of the varistor element body 20. FIG. .

  Each varistor layer 22, 24, 26 in the varistor element body 20 includes zinc oxide (ZnO) as a main component, and includes transition metal oxide, rare earth metal oxide, calcium oxide, or silicon oxide as subcomponents. It is preferable to include. This makes it possible to achieve both excellent varistor characteristics and high surge resistance at a high level.

Examples of the calcium oxide contained in the varistor layers 22, 24, and 26 include CaO and composite oxides such as CaSiO ₃ and Ca ₂ SiO ₄ containing calcium, silicon, and oxygen. Examples of the silicon oxide contained in the varistor layer _{22,24,26, SiO 2, CaSiO 3,} Ca 2 SiO 4 containing calcium and silicon and oxygen, and _Zn 2 SiO ₄ composite oxides such like. The varistor layers 22, 24, and 26 preferably include at least one oxide selected from a Co oxide or a Group IIIB element in addition to the above-described subcomponents. Examples of group IIIB elements include B, Al, Ga, and In.

  The internal electrode 34 and the via-hole electrode 32 contain a metal component including palladium or silver as a main component. The internal electrode 34 and the via-hole electrode 32 may contain oxides and glass components such as zinc oxide, barium oxide, and boron oxide in addition to the main components.

  Next, an example of a method for manufacturing the varistor 100 will be described. The method for manufacturing the varistor 100 includes a first step of forming the varistor element body 20 and a second step of forming the terminal electrode 10 on the main surface 20 a of the varistor element body 20. Hereinafter, details of each process will be described.

  In the first step, a varistor element body 20 having a laminated structure having a plurality of varistor layers and internal electrodes embedded therebetween is formed by the following procedure. First, after weighing each of zinc oxide, transition metal oxide, rare earth metal oxide, calcium oxide, silicon oxide, and other components as raw materials for the varistor layers 22, 24, and 26, Mix to prepare varistor material. The varistor raw material and the organic vehicle are kneaded to obtain a varistor layer-forming coating material (slurry). An organic vehicle is obtained by dissolving an organic binder in an organic solvent. Examples of the organic binder include ethyl cellulose and polyvinyl butyral. Examples of the organic solvent include terpineol, butyl carbitol, acetone, and toluene.

  The above slurry is applied on a film made of, for example, polyethylene terephthalate by a known method such as a doctor blade method, and then dried to form a film having a thickness of about 30 μm. The film thus obtained is peeled from the film to obtain a green sheet.

  Next, an electrode pattern corresponding to the internal electrode 34 and the via hole electrode 32 embedded in the varistor element body 20 is formed on the green sheet. The electrode pattern of the internal electrode 34 is formed, for example, by applying a conductive paste mixed with metal powder such as palladium particles, glass frit, an organic binder and an organic solvent by a screen printing method or the like and drying. Further, the electrode pattern of the via hole electrode 32 is formed by filling a via hole formed by a known method on a green sheet with a conductive paste and drying. Examples of the organic binder used for the conductive paste include ethyl cellulose and polyvinyl butyral. Examples of the organic solvent used for the conductive paste include terpineol, butyl carbitol, acetone, and toluene.

  Next, each green sheet on which the electrode pattern is formed and a green sheet on which the electrode pattern is not formed are stacked in a predetermined order as necessary to form a sheet laminate. The sheet laminate obtained in this way is cut into, for example, chips, to obtain a plurality of divided green bodies. The green body is heated at 180 to 400 ° C. for 0.5 to 24 hours to remove the binder. Thereafter, the varistor element body 20 is obtained by baking at 850 to 1400 ° C. for 0.5 to 8 hours.

A base glass layer may be provided on the main surface 20a of the varistor element body 20 as necessary. The base glass layer is, for example, dried and baked after applying a paste containing an organic binder and an organic solvent to an oxide such as SiO ₂ —ZnO—BaO—ZrO ₂ —Al ₂ O ₃ on the main surface 20a. Can be formed.

Further, a resistor may be formed on the main surface 20 a of the varistor element body 20. The resistor can be formed using a resistor paste prepared by mixing inorganic particles such as glass powder, metal oxide and metal boride, an organic binder, and an organic solvent. As the glass powder, glass such as Al ₂ O ₃ —B ₂ O ₃ —SiO ₂ can be used. For example, RuO ₂ or SnO ₂ can be used as the metal oxide. For example, LaB ₆ can be used as the metal boride. The resistor can be formed by baking the above-described resistance paste applied on the main surface 20a by a screen printing method or the like at 800 to 900 ° C. The resistor may be provided directly on the main surface 20a of the varistor element body 20, or may be provided on a base glass layer formed on the main surface 20a.

  In the second step, the terminal electrode 10 having the first layer 4 and the second layer 5 is formed on the main surface 20a of the varistor element body 20 in the following procedure. First, a conductive paste for forming the terminal electrode 10 is prepared. This conductive paste has an organic binder of 1 to 20 parts by weight, glass of 0 to 20 parts by weight, and a dispersant of 0 to 50 to 95 parts by weight of an alloy (CuNi alloy) powder containing copper and nickel as constituent elements. It can be prepared by mixing 10 to 10 parts by mass and 1 to 40 parts by mass of an organic solvent. Examples of the organic binder used here include acrylic resin, ethyl cellulose, and polyvinyl butyral. Examples of the organic solvent include terpineol, butyl carbitol, acetone, and toluene.

  The mass ratio of Ni in the CuNi alloy used here is preferably 10 to 80 mass%, more preferably 15 to 75 mass%. If the mass ratio of Ni becomes too high, the terminal electrode 10 tends to be difficult to sinter. On the other hand, if the mass ratio of Ni is too low, the terminal electrode 10 having a two-layer structure tends to be difficult to obtain.

  The prepared conductive paste is applied onto the main surface 20a of the varistor element body 20 by a screen printing method. After the application, the electrode pattern corresponding to the terminal electrode 10 is formed by drying. Thereafter, the electrode pattern is baked at 600 to 1300 ° C. for 3 to 30 minutes to form the terminal electrode 10 on the main surface 20 a of the varistor element body 20. When the baking temperature is less than 600 ° C., the sintering of the terminal electrode 10 tends not to proceed sufficiently, and when it exceeds 1300 ° C., the terminal electrode 10 tends to be oversintered. Further, if the holding time at the time of baking is less than 3 minutes, the terminal electrode 10 tends not to be sufficiently sintered, and if it exceeds 30 minutes, the terminal electrode 10 tends to be oversintered.

  The temperature rising rate during baking is preferably 10 to 200 ° C./min. If the rate of temperature increase is less than 10 ° C./min, the terminal electrode 10 tends to be oversintered, and if it exceeds 200 ° C./min, the sintering tends to be insufficient. The terminal electrode 10 may be provided so as to cover both ends of the resistor formed on the main surface 20a.

  The terminal electrode 10 needs to be baked in an atmosphere containing oxygen. From the viewpoint of simplifying the manufacturing equipment and manufacturing process, baking is preferably performed in the air. Thereby, the first layer 4 and the second layer 5 each containing an oxide can be formed. When baking is performed in an inert gas atmosphere, the terminal electrode 10 having a two-layer structure cannot be obtained.

  The terminal electrode 10 obtained by the above steps has a first layer 4 and a second layer 5 having different compositions from the varistor element body 20 side. The first layer 4 contains nickel and nickel oxide as main components. On the other hand, the second layer 5 contains copper and copper oxide as main components. The first layer 4 has a higher porosity than the second layer 5. Therefore, when a force is applied to the terminal electrode 10 in a direction parallel to the main surface 20a of the varistor element body 20, the first layer 4 is slightly distorted and can absorb the force. For this reason, the terminal electrode 10 has excellent mechanical strength. Further, since the first layer 4 disposed on the varistor element body 20 side contains nickel oxide, the adhesive strength with the varistor element body 20 is high. Thus, since the terminal electrode 10 of the present embodiment includes the first layer 4 having a high porosity and containing nickel oxide, the terminal electrode 10 is bonded to the varistor element body 20 with sufficiently high strength.

  The surface of the terminal electrode 10 may be plated to provide a plating layer. The plating treatment may be either electroless plating or electrolytic plating. For example, the plating layer is obtained by a method of sequentially forming a Ni plating layer and a Sn plating layer by a barrel plating method using a Ni plating bath (such as a Watt bath) and a Sn plating bath (such as a neutral Sn plating bath). Can do. Accordingly, a terminal electrode having a four-layer structure in which the first layer 4, the second layer 5, the Ni plating layer, and the Sn plating layer are sequentially stacked can be formed.

  Since the terminal electrode 10 includes the dense second layer 5 having a lower porosity than the first layer 4, the components of the plating solution when the plating layer is formed include the terminal electrode 10 and the varistor element. Intrusion into the inside of the body 20 and the interface between the terminal electrode 10 and the varistor element body 20 can be sufficiently suppressed. Thereby, the deterioration of the terminal electrode 10 and the varistor element body 20 and the occurrence of peeling between the terminal electrode 10 and the varistor element body 20 can be sufficiently suppressed. Therefore, even if the plating process is performed, the excellent mechanical strength of the terminal electrode 10 and the excellent adhesive force between the terminal electrode 10 and the varistor element body 20 can be sufficiently maintained. The second layer 5 contains CuO as an oxide, but is easier to remove by etching than NiO. For this reason, the plating layer which covers the 2nd layer 5 can be formed easily.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, the varistor 100 may have a glass underlayer, a resistor, and a glass protective layer covering these on the main surface 20 a of the varistor element body 20. The ceramic electronic component of the present invention is not limited to a varistor, and may be, for example, an inductor, a capacitor, or an LCR (a composite electronic component of an inductor, a capacitor and a resistor).

  The contents of the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Production of varistors]
Example 1
A slurry for forming a varistor element body was prepared by the following procedure. Zinc oxide powder, an organic binder, an organic solvent, and an additive were blended and mixed for 20 hours using a ball mill to obtain a slurry for a varistor element body.

  A conductive paste for forming external electrodes was prepared by the following procedure. As the conductive powder, a glass-coated CuNi alloy powder (Ni ratio: 10% by mass) was prepared. A total of 20 parts by mass of acrylic resin, butyl carbitol and butyl carbitol acetate was mixed with 80 parts by mass of the conductive powder, and mixed using a three-roll mill to prepare a conductive paste for terminal electrodes. .

  A varistor 100 as shown in FIG. 1 was prepared using the slurry and conductive paste prepared as described above. Specifically, first, the slurry for the varistor element body prepared as described above was applied onto a film made of polyethylene terephthalate by a doctor blade method, and then dried to form a film having a thickness of 30 μm. The film thus obtained was peeled from the film to obtain a green sheet.

  Next, an electrode pattern corresponding to the internal electrode 34 and the via hole electrode 32 was formed on the green sheet. The electrode pattern was formed by applying or pasting a conductive paste containing palladium powder into a via hole by a screen printing method and drying. Next, green sheets on which electrode patterns were formed were stacked to form a sheet laminate. The sheet laminate thus obtained was subjected to heat treatment to remove the binder, and then baked to obtain a varistor element body 20.

  On the main surface 20a of the varistor element body 20 where the end face of the via-hole electrode 32 was exposed, a conductive paste was applied by screen printing so as to cover the end face of the via-hole electrode 32. The applied conductive paste was dried with hot air and then baked in the atmosphere to produce the terminal electrode 10. The baking conditions (temperature profile) of the terminal electrode 10 were as follows: temperature rising rate: 42 ° C./min, baking temperature: 700 ° C., holding time: 10 minutes. Thus, the varistor 100 of Example 1 was obtained.

(Examples 2-11, Comparative Examples 1-6)
Except having used the CuNi alloy powder which has Ni content shown in Table 1 for preparation of an electrically conductive paste, and having changed the baking conditions of the terminal electrode 10 as shown in Table 1, it carried out similarly to Example 1, and. A varistor 100 was produced. The baking temperature was 700 ° C. for all. These were made into the varistor of Examples 2-11 and Comparative Examples 1-6.

[Evaluation of terminal electrode]
<Presence of layer structure>
The produced varistors 100 of each Example and each Comparative Example were filled with resin and polished until the cross section as shown in FIG. 1 was exposed, and the cross section was observed using a scanning electron microscope (SEM, magnification: 1500 times). did. And the distribution of the metal element and oxygen of the terminal electrode 10 was confirmed by energy dispersive X-ray analysis (EDS) of the same cross section. The terminal electrode 10 having two layers having different compositions was evaluated as “with a layer structure”, and the terminal electrode 10 having a uniform composition and a single layer was evaluated as “without a layer structure”. The evaluation results are as shown in Table 1.

<Sinterability>
The sinterability of the terminal electrode 10 was evaluated based on the SEM observation (magnification: 1500 times) of the cross section described above. “A” indicates a good sinterability, “B” indicates that the composition image has a relatively large number of black portions (voids) in contrast, and grain growth does not proceed and is not sufficiently densified. The product was evaluated as “C”, and there was abnormal growth of particles, and oversintering was evaluated as “D”. The evaluation results are as shown in Table 1.

<Invasion of plating solution>
The produced varistor 100 was subjected to Ni plating and Sn plating in order using a barrel plating apparatus. Thereafter, the varistor 100 was taken out of the plating bath and polished, and SEM observation (magnification: 1500 times) of the cross section as shown in FIG. 1 was performed. “A” indicates that no penetration of the plating solution is confirmed inside the terminal electrode 10 and the varistor element body 20 or between the terminal electrode 10 and the varistor element body 20, and “B” indicates that the penetration of the plating solution is confirmed. ". The evaluation results are as shown in Table 1.

<Adhesive strength>
The terminal electrode 10 of the produced varistor 100 and the prepared substrate were connected with solder to produce an evaluation component. Then, the varistor 100 was pulled from the fixed substrate in the direction in which the substrate and the varistor 100 face each other, and the tensile force required for the terminal electrode 10 to peel from the varistor element body 20 was measured. The case where the tensile force exceeded 1.47N was evaluated as “A”, the case where it was 0.98 to 1.47N was evaluated as “B”, and the case where it was less than 0.98N was evaluated as “C”. The evaluation results are as shown in Table 1.

<Mechanical strength>
The terminal electrode 10 of the produced varistor 100 and the prepared substrate were connected with solder to produce an evaluation component. The substrate was fixed, and the varistor 100 was pushed in a direction perpendicular to the opposing direction of the varistor 100 and the substrate, and the pressing force required to break the terminal electrode was measured. The case where the pressing force exceeded 1.47N was evaluated as “A”, the case where 0.98 to 1.47N was evaluated as “B”, and the case where it was less than 0.98N was evaluated as “C”. The evaluation results are as shown in Table 1.

  From the results of SEM observation and EDS, the terminal electrodes 10 of Examples 1 to 11 contain the first layer 4 containing Ni element as the main element and the Cu element as the main element from the varistor element body 20 side. It was confirmed that the second layer 5 was separated into two layers. In addition, it was confirmed that the first layer 4 of Examples 1 to 11 had a higher porosity than the second layer 5 because of a higher contrast black portion. On the other hand, all of the terminal electrodes 10 of Comparative Examples 1 to 6 had a single composition and did not have a two-layer structure.

  In any of the examples and comparative examples, oxygen was not detected in the electrode pattern that is a precursor of the terminal electrode 10 in the sample before the terminal electrode 10 was baked in the atmosphere. On the other hand, in the EDS analysis of the cross section shown in FIG. 1 of the varistor 100 of each example obtained by baking in the atmosphere, oxygen was detected in both the first layer 4 and the second layer 5. Therefore, it was confirmed that the first layer 4 and the second layer 5 contain nickel oxide and copper oxide, respectively.

  Next, the thicknesses of the first layer 4 and the second layer 5 at the center of the terminal electrode 10 were measured using SEM images of the cross sections of the terminal electrodes of Examples 2, 3, and 5, respectively. Moreover, Ni content of the 1st layer 4 and the 2nd layer 5 was measured by EDS. In addition, a black portion with a contrast in the composition image was determined as a void, and the ratio of the area of the void to the entire area of the composition image was converted into a volume ratio to calculate the porosity. These results are summarized in Table 2.

  ADVANTAGE OF THE INVENTION According to this invention, the adhesive force with a ceramic element | base_body can be provided, and the terminal electrode for ceramic electronic components which has the outstanding electroconductivity and the outstanding mechanical strength can be provided. In addition, a ceramic electronic component having high reliability can be provided.

  DESCRIPTION OF SYMBOLS 4 ... 1st layer, 5 ... 2nd layer, 10 ... Terminal electrode, 20 ... Varistor body (ceramic body), 22, 24, 26 ... Varistor layer, 32 ... Via-hole electrode, 34 ... Internal electrode, 100 ... varistors (ceramic electronic components).

Claims (3)

A terminal electrode for a ceramic electronic component provided on a ceramic body,
From the ceramic body side, comprising a first layer containing nickel and nickel oxide, and a second layer containing copper and copper oxide,
The first electrode is a terminal electrode having a higher porosity than the second layer.   The terminal electrode according to claim 1, wherein the porosity of the first layer is 5 to 30% by volume, and the porosity of the second layer is less than 5% by volume. A ceramic electronic component comprising a ceramic body and the terminal electrode according to claim 1 or 2 on the ceramic body.

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