Electronic component

Abstract

This electronic component comprises an element body (20), an inorganic oxide layer (30) that covers the outer surface (21) of the element body (20), and a glass layer (50) that covers the outer surface (31) of the inorganic oxide layer (30). The glass layer (50) contains one or more elements selected from alkali metals and alkaline earth metals. In the inorganic oxide layer (30), the concentration of the same element as one or more elements selected from the alkali metal and the alkaline earth metal contained in the glass layer (50) is less than the concentration of the same element in the glass layer (50).

Description

Electronic Components

[0001] The present disclosure relates to electronic components.

[0002] The electronic component described in Patent Document 1 includes an element body and external electrodes. The external electrodes cover a portion of the outer surface of the element body. A Ni plating film and a Sn plating film are laminated on the external electrodes. The electronic component described in Patent Document 1 also includes a glass film. The glass film covers the portion of the outer surface of the element body that is not covered by the external electrodes. The glass film contains two or more alkali metal elements selected from Li, Na, and K.

[0003] Japanese Patent Application Laid-Open No. 2004-128488

[0004] In the electronic component described in Patent Document 1, the alkali metal contained in the glass film may cause elements contained in the element body to diffuse into the glass layer, which may change the atomic structure of the element body and result in changes in the characteristics of the element body.

[0005] In order to solve the above-mentioned problems, the present disclosure provides an electronic component comprising an element body, an inorganic oxide layer covering an outer surface of the element body, and a glass layer covering the outer surface of the inorganic oxide layer, wherein the glass layer contains one or more elements selected from alkali metals and alkaline earth metals, and the concentration of an element in the inorganic oxide layer that is the same as the one or more elements selected from alkali metals and alkaline earth metals contained in the glass layer is lower than the concentration of the same element in the glass layer.

[0006] According to the above configuration, it is possible to suppress the elements of the element body from diffusing into the glass layer.

[0007] Fig. 1 is a perspective view of an electronic component. Fig. 2 is a side view of the electronic component. Fig. 3 is a cross-sectional view taken along line 3-3 in Fig. 2. Fig. 4 is an enlarged cross-sectional view of an element body, an inorganic oxide layer, and a glass layer. Fig. 5 is an explanatory diagram illustrating a method for manufacturing an electronic component.

[0008] An embodiment of an electronic component will be described below with reference to the drawings. Note that the drawings may show components enlarged to facilitate understanding. The dimensional proportions of the components may differ from those in the actual drawings or from those in other drawings.

[0009] 1, the electronic component 10 is, for example, a surface-mount type negative temperature coefficient thermistor component mounted on a circuit board, etc. Note that a negative temperature coefficient thermistor component has the characteristic that its resistance value decreases as the temperature increases.

[0010] The electronic component 10 includes an element body 20. The element body 20 is generally rectangular prism-shaped and has a central axis CA. In the following description, an axis extending along the central axis CA is referred to as a first axis X. One of the axes perpendicular to the first axis X is referred to as a second axis Y. An axis perpendicular to the first axis X and the second axis Y is referred to as a third axis Z. One of the directions along the first axis X is referred to as a first positive direction X1, and the direction along the first axis X that is opposite to the first positive direction X1 is referred to as a first negative direction X2. One of the directions along the second axis Y is referred to as a second positive direction Y1, and the direction along the second axis Y that is opposite to the second positive direction Y1 is referred to as a second negative direction Y2. One of the directions along the third axis Z is referred to as a third positive direction Z1, and the direction along the third axis Z that is opposite to the third positive direction Z1 is referred to as a third negative direction Z2.

[0011] The outer surface 21 of the element body 20 has six flat surfaces. The term "surface" of the element body 20 as used herein refers to a surface that can be observed when the entire element body 20 is observed. In other words, even if there are minute irregularities or steps that are not visible unless a portion of the element body 20 is magnified and observed using a microscope or the like, the surface is still referred to as a flat or curved surface. The six flat surfaces face in different directions. The six flat surfaces are broadly divided into a first end surface 22A facing the first positive direction X1, a second end surface 22B facing the first negative direction X2, and four side surfaces 22C. The four side surfaces 22C are, respectively, a surface facing the third positive direction Z1, a surface facing the third negative direction Z2, a surface facing the second positive direction Y1, and a surface facing the second negative direction Y2.

[0012] In the outer surface 21 of the element body 20, the boundary portions between two adjacent flat surfaces and the boundary portions between three adjacent surfaces are curved. That is, the corners of the element body 20 are rounded and chamfered. In Figures 1 and 2, the outer surface 31 of the inorganic oxide layer 30 and the outer surface 51 of the glass layer 50, which will be described later, are identified with the outer surface 21 of the element body 20 and are assigned reference numerals thereto.

[0013] As shown in Fig. 2, the element body 20 has a larger dimension along the first axis X than along the third axis Z. Also, as shown in Fig. 1, the element body 20 has a larger dimension along the first axis X than along the second axis Y. The material of the element body 20 is a ceramic obtained by firing a metal oxide containing one or more elements selected from Mn, Fe, Ni, Co, Ti, Ba, Al, and Zn.

[0014] 3 , the electronic component 10 includes two first internal electrodes 41 and two second internal electrodes 42. The first internal electrodes 41 and the second internal electrodes 42 are embedded inside the element body 20.

[0015] The first internal electrode 41 is made of a conductive material. For example, the first internal electrode 41 is made of palladium. The second internal electrode 42 is made of the same material as the first internal electrode 41.

[0016] The first internal electrode 41 has a rectangular plate shape. The main surface of the first internal electrode 41 is perpendicular to the second axis Y. The second internal electrode 42 has the same rectangular plate shape as the first internal electrode 41. The main surface of the second internal electrode 42 is perpendicular to the second axis Y, similar to the first internal electrode 41.

[0017] The dimension of the first internal electrode 41 in the direction along the first axis X is smaller than the dimension of the element body 20 in the direction along the first axis X. Also, as shown in Fig. 1 , the dimension of the first internal electrode 41 in the direction along the third axis Z is approximately two-thirds of the dimension of the element body 20 in the direction along the third axis Z. The dimensions of the second internal electrode 42 in each direction are approximately the same as those of the first internal electrode 41.

[0018] 3, the first internal electrodes 41 and the second internal electrodes 42 are positioned alternately in the direction along the second axis Y. That is, the first internal electrodes 41, the second internal electrodes 42, the first internal electrodes 41, and the second internal electrodes 42 are arranged in this order from the side surface 22C facing the second positive direction Y1 toward the second negative direction Y2. In this embodiment, the distances between the internal electrodes in the direction along the second axis Y are equal.

[0019] 1, the two first internal electrodes 41 and the two second internal electrodes 42 are both located at the center of the element body 20 in the direction along the third axis Z. On the other hand, as shown in Fig. 3, the first internal electrodes 41 are located closer to the first positive direction X1, and the second internal electrodes 42 are located closer to the first negative direction X2.

[0020] Specifically, the end of the first internal electrode 41 on the first positive direction X1 side coincides with the end of the element body 20 on the first positive direction X1 side. The end of the first internal electrode 41 on the first negative direction X2 side is located inside the element body 20 and does not reach the end of the element body 20 on the first negative direction X2 side. On the other hand, the end of the second internal electrode 42 on the first negative direction X2 side coincides with the end of the element body 20 on the first negative direction X2 side. The end of the second internal electrode 42 on the first positive direction X1 side is located inside the element body 20 and does not reach the end of the element body 20 on the first positive direction X1 side.

[0021] As shown in Figure 3, the electronic component 10 includes an inorganic oxide layer 30. The inorganic oxide layer 30 covers the outer surface 21 of the element body 20. In this embodiment, the inorganic oxide layer 30 covers substantially the entire area of ​​the outer surface 21 of the element body 20. Note that "the inorganic oxide layer 30 covers the outer surface 21 of the element body 20" means that the inorganic oxide layer 30 covers at least a portion of the outer surface 21. In addition, even if the inorganic oxide layer 30 and the outer surface 21 are not in close contact with each other, and no other solid substance is present between the inorganic oxide layer 30 and the outer surface 21, this also applies to "the inorganic oxide layer 30 covers the outer surface 21 of the element body 20."

[0022] The inorganic oxide layer 30 contains one or more specific elements selected from Al, Si, Zr, and Ti. In this embodiment, the inorganic oxide layer 30 is made of alumina. That is, the inorganic oxide layer 30 contains Al. Whether or not the inorganic oxide layer 30 contains Al can be confirmed by the following method. First, the electronic component 10 is ground in a direction perpendicular to the outer surface 21 of the element body 20 by focused ion beam processing or the like. Next, the ground cross section is imaged using a transmission electron microscope (TEM). The imaged cross section is then subjected to energy dispersive X-ray spectroscopy (EDX) to obtain mapping data of the composition of the cross section. The mapping data is in the form of an image. In the mapping data, the higher the dose of characteristic X-rays, the higher the brightness value in the image. If a luminance value equal to or greater than a certain level is obtained in the portion of the mapping data that indicates the inorganic oxide layer 30, it is determined that "Al is contained as a specific element."

[0023] The electronic component 10 includes a glass layer 50. The glass layer 50 covers the outer surface 31 of the inorganic oxide layer 30. Specifically, the glass layer 50 covers substantially the entire area of ​​the outer surface 31 of the inorganic oxide layer 30.

[0024] The glass layer 50 contains the same element as the specific element contained in the inorganic oxide layer 30. That is, the glass layer 50 contains Al. The Al diffuses from the inorganic oxide layer 30 into the glass layer 50 when the glass layer 50 is formed on the outer surface 31 of the inorganic oxide layer 30. In the glass layer 50, the Al concentration decreases with increasing distance from the inorganic oxide layer 30 in the thickness direction of the glass layer 50. In other words, the Al concentration in the glass layer 50 has a gradient composition in which the Al concentration decreases with increasing distance from the inorganic oxide layer 30 in the thickness direction of the glass layer 50. The Al concentration in the glass layer 50 can be confirmed by the following method. First, the electronic component 10 is ground in a direction perpendicular to the outer surface 21 of the element body 20 by focused ion beam processing or the like. Next, the ground cross section is imaged using a transmission electron microscope. Then, mapping data of the composition in the cross section is obtained by energy dispersive X-ray spectroscopy. The mapping data is in the form of an image. In the mapping data, the higher the dose of characteristic X-rays in a location, the higher the luminance value in the image. In other words, in the mapping data, the higher the amount of composition in a location, the higher the luminance value in the image. Therefore, the concentration of the composition in a specific region of this mapping data is calculated by dividing the sum of the luminance values ​​present in that region by the area of ​​that region. Note that the concentration in this case is expressed as the average luminance value per unit area.

[0025] The glass layer 50 contains one or more elements selected from alkali metals and alkaline earth metals. Specifically, the glass layer 50 contains potassium. The potassium concentration in the glass layer 50 increases as the glass layer 50 approaches the inorganic oxide layer 30. Whether the glass layer 50 contains Al and whether the glass layer 50 contains potassium can be confirmed in the same manner as described above.

[0026] The melting point of the glass layer 50 is lower than that of the inorganic oxide layer 30. In other words, the melting point of the inorganic oxide layer 30 is higher than that of the glass layer 50. Therefore, even if heat is applied to the inorganic oxide layer 30 in the process of forming the glass layer 50, the inorganic oxide layer 30 does not melt completely.

[0027] The electronic component 10 includes a first external electrode 61 and a second external electrode 62. In FIGS. 1 to 3 , the first external electrode 61 and the second external electrode 62 are indicated by dashed two-dot lines. As shown in FIG. 3 , the first external electrode 61 includes a first base electrode 61A and a first metal layer 61B. The first base electrode 61A is laminated on the glass layer 50 in a portion of the outer surface 21 of the element body 20, including the first end face 22A. Specifically, the first base electrode 61A is a five-sided electrode that covers the first end face 22A of the element body 20 and portions of the four side faces 22C facing the first positive direction X1. In this embodiment, the first base electrode 61A is made of a mixture of silver and glass.

[0028] The first metal layer 61B externally covers the first base electrode 61A, and is therefore stacked on the first base electrode 61A. Although not shown, the first metal layer 61B has a two-layer structure consisting of a nickel layer and a tin layer in this order from the first base electrode 61A side.

[0029] The second external electrode 62 has a second base electrode 62A and a second metal layer 62B. The second base electrode 62A is laminated on the glass layer 50 in a portion of the outer surface 21 of the element body 20, including the second end face 22B. Specifically, the second base electrode 62A is a five-sided electrode that covers the second end face 22B of the element body 20 and portions of the four side faces 22C facing the first negative direction X2. In this embodiment, the material of the second base electrode 62A is the same as the material of the first external electrode 61, which is a mixture of silver and glass.

[0030] The second metal layer 62B externally covers the second base electrode 62A, i.e., the second metal layer 62B is laminated on the second base electrode 62A. Similar to the first metal layer 61B, the second metal layer 62B has a two-layer structure consisting of, in order from the element body 20 side, a nickel layer and a tin layer.

[0031] The second external electrode 62 does not reach the first external electrode 61 on the side surface 22C, and is spaced apart from the first external electrode 61 in the direction along the first axis X. In addition, the first external electrode 61 and the second external electrode 62 are not stacked in the central portion of the side surface 22C of the element body 20 in the direction along the first axis X, and the glass layer 50 is exposed.

[0032] 3 , the first external electrode 61 is connected to the end of the first internal electrode 41 on the first positive direction X1 side via a first penetrating portion 71 that penetrates the inorganic oxide layer 30 and the glass layer 50. Note that, as will be described in detail later, the first penetrating portion 71 is formed when palladium constituting the first internal electrode 41 extends toward the first external electrode 61 during the manufacturing process of the electronic component 10.

[0033] The second external electrode 62 is connected to the end of the second internal electrode 42 on the first negative direction X2 side via a second through portion 72 that penetrates the inorganic oxide layer 30 and the glass layer 50. Similar to the first through portion 71, the second through portion 72 is formed during the manufacturing process of the electronic component 10 by the palladium that constitutes the second internal electrode 42 extending toward the second external electrode 62 side.

[0034] 3, the first internal electrode 41 and the first through portion 71 are illustrated as separate members with a boundary therebetween, but in reality, there is no clear boundary between them. The same applies to the second through portion 72. Furthermore, the first through portion 71 and the second through portion 72 are not shown in FIGS. 1 and 2.

[0035] <Regarding the Inorganic Oxide Layer> As shown in FIG. 4 , the average thickness T1 of the inorganic oxide layer 30 is thinner than the average thickness T2 of the glass layer 50. The average thickness T1 of the inorganic oxide layer 30 is calculated as follows. First, an electron microscope is used to image a cross section of the element body 20. In the image, a measurement range of at least 10 μm is set in the direction along the outer surface 31 of the inorganic oxide layer 30. Then, image processing is used to calculate the cross-sectional area of ​​the inorganic oxide layer 30 in the measurement range. Next, the cross-sectional area is divided by the length of the measurement range in the direction along the outer surface 31 of the inorganic oxide layer 30. In this way, the average thickness T1 of the inorganic oxide layer 30 in the measurement range is calculated. In other words, the average thickness T1 of the inorganic oxide layer 30 is the average thickness in the measurement range. The average thickness T2 of the glass layer 50 can also be measured in a similar manner. Note that in FIG. 4 , the thickness T1 represents an example of the thickness of the inorganic oxide layer 30. The same applies to the thickness T2 of the glass layer 50.

[0036] The inorganic oxide layer 30 contains one or more elements selected from alkali metals and alkaline earth metals contained in the glass layer 50. In this embodiment, the inorganic oxide layer 30 contains potassium. The concentration of potassium contained in the inorganic oxide layer 30 is lower than the concentration of potassium in the glass layer 50. That is, the concentration of elements in the inorganic oxide layer 30 that are the same as the one or more elements selected from alkali metals and alkaline earth metals contained in the glass layer 50 is lower than the concentration of the same elements in the glass layer 50. The potassium concentration in the inorganic oxide layer 30 can be confirmed in the same manner as above.

[0037] <Method for Manufacturing Electronic Component> Next, a method for manufacturing electronic component 10 and a method for forming inorganic oxide layer 30 will be described. As shown in Figure 5, the method for manufacturing electronic component 10 includes a laminate preparation step S11, an R-chamfering step S12, a first film-forming step S13, a solvent-adding step S14, a catalyst-adding step S15, an element-adding step S16, a polymer-adding step S17, and a metal alkoxide-adding step S18. The method for manufacturing electronic component 10 also includes a second film-forming step S19, a first drying step S20, an immersion step S21, a second drying step S22, a conductor-applying step S23, a curing step S24, and a plating step S25.

[0038] First, in forming the element body 20, in the laminate preparation step S11, a laminate is prepared, which is the element body 20 in the shape of a rectangular parallelepiped having six flat surfaces. That is, the laminate at this stage is in a state before R-chamfering. For example, first, a plurality of ceramic sheets that will become the element body 20 are prepared. The sheets are thin plates. A conductive paste that will become the first internal electrode 41 is laminated on the sheets. A ceramic sheet that will become the element body 20 is laminated on the conductive paste. A conductive paste that will become the second internal electrode 42 is laminated on the sheet. In this way, the ceramic sheets and the conductive paste are laminated. Then, by cutting to a predetermined size, an unfired laminate is formed. Thereafter, the unfired laminate is fired at a high temperature to prepare the laminate.

[0039] Next, an R-chamfering process S12 is performed. In the R-chamfering process S12, curved surfaces are formed at the boundary portions between two adjacent flat surfaces and at the boundary portions between three adjacent flat surfaces of the laminate prepared in the laminate preparation process S11. For example, the corners of the laminate are R-chamfered by barrel polishing, thereby forming curved surfaces at the boundary portions. In this way, the element body 20 is formed.

[0040] Next, a first film-forming step S13 is performed. In the first film-forming step S13, an alumina film is formed as the inorganic oxide layer 30. Specifically, the alumina film is formed on the outer surface 21 of the element body 20 by a sputtering method. At this stage, the inorganic oxide layer 30 does not contain potassium.

[0041] Next, a solvent introduction step S14 is performed. In the solvent introduction step S14, 2-propanol is introduced into the reaction vessel as a solvent. Next, a catalyst introduction step S15 is performed. In the catalyst introduction step S15, first, stirring of the solvent in the reaction vessel is started. Then, ammonia water is introduced into the reaction vessel as an aqueous solution containing a catalyst. The catalyst in this embodiment is hydroxide ions, and functions as a catalyst for promoting the hydrolysis of the metal alkoxide, which will be described later.

[0042] Next, the element introduction step S16 is performed. In the element introduction step S16, a plurality of element bodies 20 formed in advance as described above are introduced into the reaction vessel prepared in the catalyst introduction step S15. Next, the polymer introduction step S17 is performed. In the polymer introduction step S17, polyvinylpyrrolidone is introduced into the reaction vessel as a polymer. As a result, the polymer introduced into the reaction vessel is adsorbed onto the inorganic oxide layer 30.

[0043] Next, a metal alkoxide introduction step S18 is performed. In the metal alkoxide introduction step S18, liquid tetraethyl orthosilicate is introduced into the reaction vessel as the metal alkoxide. Tetraethyl orthosilicate is also called tetraethoxysilane. In this embodiment, the amount of metal alkoxide introduced in the metal alkoxide introduction step S18 is calculated based on the area of ​​the outer surface 21 of the element bodies 20 introduced in the element introduction step S16. Specifically, the amount of metal alkoxide introduced in the metal alkoxide introduction step S18 is calculated by multiplying the amount of metal alkoxide per element body 20 required to form the glass layer 50 by the number of element bodies 20.

[0044] Next, a second film-forming step S19 is performed. In the second film-forming step S19, the stirring of the solvent started in the solvent-adding step S14 is continued for a predetermined time after the metal alkoxide is added to the reaction vessel in the metal alkoxide-adding step S18. In this way, in the second film-forming step S19, a glass layer 50 is formed by a liquid-phase reaction in the reaction vessel.

[0045] Next, a first drying step S20 is performed. In the first drying step S20, after stirring is continued for a predetermined time in the second film-forming step S19, the element body 20 is removed from the reaction vessel and dried. As a result, the sol-state glass layer 50 is dried and becomes a gel-state glass layer 50.

[0046] Next, an immersion step S21 is performed. In the immersion step S21, a solution containing at least one element selected from alkali metals and alkaline earth metals as an additive is first placed in a reaction vessel different from the reaction vessel used up to the second film-forming step S19. In this embodiment, the solution is an aqueous solution containing a potassium oxide precursor. Then, the element body 20 having the gelled glass layer 50 is immersed in the solution. This causes the solution to adhere to the surface of the glass layer 50. In the immersion step S21, the potassium oxide precursor as an additive adheres to the surface of the glass layer 50. The amount of the potassium oxide precursor adhering to the outer surface 51 of the glass layer 50 depends on the concentration of the potassium oxide precursor in the solution prepared in the immersion step S21.

[0047] Next, a second drying step S22 is performed. In the second drying step S22, the element body 20 immersed in the solution in the immersion step S21 is removed from the reaction vessel and dried. This causes the water in the solution adhering to the surface of the glass layer 50 to evaporate. Meanwhile, the potassium oxide precursor contained in the solution precipitates on the outer surface 51 of the glass layer 50.

[0048] Next, a conductor application step S23 is performed. In the conductor application step S23, a conductor paste is applied to two locations on the surface of the glass layer 50: a portion including a portion covering the first end face 22A of the element body 20, and a portion including a portion covering the second end face 22B of the element body 20. Specifically, the conductor paste is applied to cover the entire first end face 22A and portions of the four side faces 22C of the glass layer 50. The conductor paste is also applied to cover the entire second end face 22B and portions of the four side faces 22C of the glass layer 50.

[0049] Next, a curing step S24 is performed. Specifically, in the curing step S24, the glass layer 50 and the element body 20 to which the conductive paste has been applied are heated. The heating temperature at this time is equal to or higher than the melting point of the glass layer 50 and lower than the melting point of the inorganic oxide layer 30, for example, approximately 800°C. As a result, the precipitated potassium oxide precursor becomes potassium oxide. The potassium oxide diffuses into the glass layer 50. Note that the amount of potassium oxide diffusing into the glass layer 50 at this time depends on the amount of potassium oxide precursor attached to the outer surface 51 of the glass layer 50. Note that the potassium oxide also flows into the inorganic oxide layer 30.

[0050] Furthermore, in the hardening step S24, the element body 20 is heated, thereby vaporizing water and polymer from the gel-like glass layer 50. This causes the glass layer 50 to be baked and hardened. As described above, the melting point of the inorganic oxide layer 30 is higher than the melting point of the glass layer 50. Therefore, the inorganic oxide layer 30 is not completely melted in the hardening step S24. Furthermore, in the hardening step S24, the conductive paste applied in the conductive material application step S23 is baked, thereby forming the first base electrode 61A and the second base electrode 62A.

[0051] In this embodiment, during heating in the curing step S24, the Kirkendall effect, which arises from the difference in diffusion rate between the first internal electrode 41 and the first base electrode 61A, attracts palladium contained in the first internal electrode 41 toward the first base electrode 61A containing silver. As a result, the first penetrating portion 71 extends from the first internal electrode 41 toward the first base electrode 61A, penetrating the inorganic oxide layer 30 and the glass layer 50, thereby connecting the first internal electrode 41 and the first base electrode 61A. The same applies to the second penetrating portion 72 connecting the second internal electrode 42 and the second base electrode 62A.

[0052] Next, a plating step S25 is performed. Electroplating is performed on the first base electrode 61A and the second base electrode 62A. As a result, a first metal layer 61B is formed on the surface of the first base electrode 61A. Furthermore, a second metal layer 62B is formed on the surface of the second base electrode 62A. Although not shown, the first metal layer 61B and the second metal layer 62B are electroplated with two types of metal, nickel and tin, to form a two-layer structure. In this manner, the electronic component 10 is formed.

[0053] Effects of this embodiment (1) The alkali metal or alkaline earth metal contained in the glass layer 50 easily breaks the bonds between atoms in the glass layer 50. As a result of the bond breaking, a large amount of non-bridging oxygen is generated, which causes element diffusion. Therefore, it is preferable that the concentrations of alkali metal elements and alkaline earth elements are low in the layer in contact with the element body 20. According to the above embodiment, the potassium concentration in the inorganic oxide layer 30 is lower than the potassium concentration in the glass layer 50. Therefore, the bonds in the inorganic oxide layer 30 are less likely to break, and the diffusion of elements contained in the element body 20 can be suppressed.

[0054] (2) If the melting point of the inorganic oxide layer 30 is lower than the melting point of the glass layer 50, the inorganic oxide layer 30 may melt during the formation of the glass layer 50. If the inorganic oxide layer 30 melts, the glass layer 50 and the inorganic oxide layer 30 may mix, and potassium contained in the glass layer 50 may flow toward the outer surface 21 of the element body 20. In the above embodiment, the melting point of the inorganic oxide layer 30 is higher than the melting point of the glass layer 50. Therefore, melting of the inorganic oxide layer 30 during the process of forming the glass layer 50, as described above, can be suppressed.

[0055] (3) In the above embodiment, the inorganic oxide layer 30 contains Al as a specific element. If the inorganic oxide layer 30 contains Al, it is easy to obtain an inorganic oxide layer 30 with excellent chemical resistance, heat resistance, and the like.

[0056] (4) In the above embodiment, the glass layer 50 contains the same type of element as the specific element contained in the inorganic oxide layer 30. In other words, the specific element in the inorganic oxide layer 30 is diffused into the glass layer 50. As a result of the specific element diffusing into the glass layer 50, the boundary between the glass layer 50 and the inorganic oxide layer 30 is less likely to be clearly defined. Therefore, peeling between these layers is less likely to occur.

[0057] (5) In the above embodiment, the Al concentration in the glass layer 50 has a gradient composition in which the concentration decreases with increasing distance from the inorganic oxide layer 30 in the thickness direction of the glass layer 50. In other words, the specific element diffused from the inorganic oxide layer 30 is concentrated in the glass layer 50 near the boundary with the inorganic oxide layer 30. With this configuration, the boundary between the glass layer 50 and the inorganic oxide layer 30 is less clearly defined. Therefore, peeling between these layers is less likely to occur.

[0058] (6) In the above embodiment, the average thickness T1 of the inorganic oxide layer 30 is smaller than the average thickness T2 of the glass layer 50. With this configuration, the inorganic oxide layer 30 is thin, so that the overall external dimensions of the electronic component 10 can be prevented from becoming larger.

[0059] <Modifications> The above embodiment and the following modifications can be implemented in combination with each other within the scope of technical inconsistency.

[0060] In the above embodiment, the electronic component 10 is not limited to a negative temperature coefficient thermistor component. For example, the electronic component 10 may be a thermistor component other than a negative temperature coefficient thermistor component, a multilayer capacitor component, or an inductor component, as long as it has some kind of wiring inside the element body 20.

[0061] In the above embodiment, the material of the element body 20 is not limited to the example in the above embodiment. The material of the element body 20 may be a composite body of resin and metal powder. In the above embodiment, the shape of the element body 20 is not limited to the example in the above embodiment. For example, the element body 20 may be a polygonal columnar shape other than a quadrangular columnar shape having a central axis CA. Furthermore, the element body 20 may be the core of a wire-wound inductor component. For example, the core may have a so-called drum core shape. Specifically, the core may have a columnar winding core portion and flange portions provided at each end of the winding core portion.

[0062] In the above embodiment, the boundary portion between adjacent flat surfaces on the outer surface 21 of the element body 20 does not have to be chamfered. In this case, there is no curved surface at the boundary portion. In the above embodiment, the shapes of the first internal electrodes 41 and the second internal electrodes 42 are not important as long as they ensure electrical conduction with the corresponding first external electrodes 61 and second external electrodes 62. Furthermore, the number of first internal electrodes 41 and second internal electrodes 42 is not important, and the number of each internal electrode may be one, or three or more.

[0063] In the above embodiment, the configuration of the first external electrode 61 is not limited to the example of the above embodiment. For example, the first external electrode 61 may be composed of only the first base electrode 61A, or the first metal layer 61B may not have a two-layer structure. The same applies to the second external electrode 62.

[0064] In the above embodiment, the first base electrode 61A does not have to contain glass as long as it is electrically connected to the first internal electrode 41. Similarly, the second base electrode 62A does not have to contain glass as long as it is electrically connected to the second internal electrode 42.

[0065] In the above embodiment, the combination of materials for the first internal electrode 41 and the first base electrode 61A is not limited to palladium and silver. For example, it may be copper and nickel, copper and silver, silver and gold, nickel and cobalt, or nickel and gold. It may also be silver on one side and silver and palladium on the other side. It may also be palladium on one side and silver and palladium on the other side, or copper on one side and silver and palladium on the other side. It may also be gold on one side and silver and palladium on the other side.

[0066] Depending on the combination of the first internal electrode 41 and the first base electrode 61A, the Kirkendall effect may not be achieved. In this case, the first internal electrode 41 may be exposed by processing the first internal electrode 41 before forming the external electrode. For example, the first end face 22A side of the element body 20 may be polished to physically remove a portion of the glass layer 50 and the inorganic oxide layer 30. The first base electrode 61A may then be formed on the exposed first internal electrode 41, thereby connecting the first internal electrode 41 and the first base electrode 61A. Alternatively, for example, after forming the first base electrode 61A, the inorganic oxide layer 30 and the glass layer 50 may be formed on the surface of the first base electrode 61A, and the inorganic oxide layer 30 and the glass layer 50 covering the surface of the first base electrode 61A may then be removed. This also applies to the combination of materials for the second internal electrode 42 and the second base electrode 62A.

[0067] In the above embodiment, the location of the first external electrode 61 is not limited to the example in the above embodiment. For example, the first external electrode 61 may be disposed only on the first end surface 22A and one side surface 22C. The same applies to the second external electrode 62.

[0068] In the above embodiment, in the portion of the glass layer 50 that is covered with the first base electrode 61A, the glass of the glass layer 50 may be integrated with the glass of the first base electrode 61A.

[0069] In the above embodiment, the inorganic oxide layer 30 does not have to cover the entire outer surface 21 of the element body 20. The inorganic oxide layer 30 only needs to cover at least a portion of the outer surface 21 of the element body 20. Similarly, the glass layer 50 does not have to cover the entire outer surface 31 of the inorganic oxide layer 30.

[0070] In the above embodiment, the inorganic oxide layer 30 does not necessarily contain alkali metals and alkaline earth metals. For example, when the inorganic oxide layer 30 contains only small amounts of alkali metals and alkaline earth metals, the alkali metals and alkaline earth metals may not be detected in the inorganic oxide layer 30 by the method described in the above embodiment. When the proportion of alkali metals and alkaline earth metals in the inorganic oxide layer 30 is so small that they are not detectable, it can be said that the inorganic oxide layer 30 does not contain alkali metals and alkaline earth metals.

[0071] In the above embodiment, the one or more elements selected from alkali metals and alkaline earth metals contained in the glass layer 50 are not limited to potassium. Similarly, the one or more elements selected from alkali metals and alkaline earth metals contained in the inorganic oxide layer 30 may be the same type of elements as those contained in the glass layer 50, and are not limited to potassium.

[0072] In the above embodiment, the potassium concentration in the glass layer 50 does not need to be higher overall as it approaches the inorganic oxide layer 30. For example, depending on the thickness T1 of the inorganic oxide layer 30, the potassium concentration may be highest at the outer surface 51 of the glass layer 50.

[0073] In the above embodiment, the average value of the thickness T1 of the inorganic oxide layer 30 may be greater than the average value of the thickness T2 of the glass layer 50. Furthermore, the average value of the thickness T1 of the inorganic oxide layer 30 may be the same as the average value of the thickness T2 of the glass layer 50.

[0074] In the above embodiment, as long as the shape of the inorganic oxide layer 30 is maintained, the melting point of the inorganic oxide layer 30 may be lower than or the same as the melting point of the glass layer 50. In the above embodiment, the specific element contained in the inorganic oxide layer 30 is not limited to Al. In consideration of chemical resistance, heat resistance, and the like, it is preferable that the inorganic oxide layer 30 contains one or more specific elements selected from Al, Si, Zr, and Ti. Similarly, the specific element contained in the glass layer 50 is not limited to Al and may be any of the above elements.

[0075] In the above embodiment, the method for forming the inorganic oxide layer 30 in the first film-forming step S13 is not limited to sputtering. For example, the inorganic oxide layer 30 may be formed by spray coating, slurry coating, or the like. The inorganic oxide layer 30 may also be formed by adding water vapor to the sputtering method. The inorganic oxide layer 30 may also be formed by atomic layer deposition modeling or the like.

[0076] In the above embodiment, the inorganic oxide layer 30 does not necessarily contain the specific element. Similarly, the glass layer 50 does not necessarily contain the specific element. In the above embodiment, the specific element in the glass layer 50 does not necessarily have to have a gradient composition in which the concentration decreases with increasing distance from the inorganic oxide layer 30 in the thickness direction of the glass layer 50.

[0077] In the above embodiment, the additive contained in the solution introduced into the reaction vessel in the immersion step S21 is not limited to the potassium oxide precursor. For example, the additive contained in the solution may be lithium carbonate, lithium chloride, lithium titanate, lithium nitride, lithium peroxide, lithium citrate, lithium fluoride, lithium hexafluorophosphate, lithium acetate, lithium iodide, lithium hypochlorite, lithium tetraborate, lithium bromide, lithium nitrate, lithium hydroxide, lithium aluminum hydride, lithium triethylborohydride, lithium hydride, lithium amide, lithium imide, lithium diisopropylamide, lithium tetramethylpiperidide, lithium sulfide, lithium sulfate, lithium thiophenolate, lithium phenoxide, or the like.

[0078] The additives contained in the solution may be, for example, oxoacid salts such as calcium carbonate, calcium bicarbonate, calcium nitrate, calcium sulfate, calcium sulfite, calcium silicate, calcium phosphate, calcium pyrophosphate, calcium hypochlorite, calcium chlorate, calcium perchlorate, calcium bromate, calcium iodate, calcium arsenite, calcium chromate, calcium tungstate, calcium molybdate, calcium magnesium carbonate, and hydroxyapatite. The additives may also be calcium acetate, calcium gluconate, calcium citrate, calcium malate, calcium lactate, calcium benzoate, calcium stearate, calcium aspartate, and the like.

[0079] The additives contained in the solution may be, for example, barium sulfite, barium chloride, barium chlorate, barium perchlorate, barium peroxide, barium chromate, barium acetate, barium cyanide, barium bromide, barium oxalate, barium nitrate, barium hydroxide, barium hydride, barium carbonate, barium iodide, barium sulfide, barium sulfate, or sodium acetate, sodium citrate.

[0080] The additives contained in the solution include, for example, potassium arsenide, potassium bromide, potassium carbonate, potassium chloride, potassium fluoride, potassium hydride, potassium iodide, potassium triiodide, potassium azide, potassium nitride, potassium superoxide, potassium ozonate, potassium peroxide, potassium phosphide, potassium sulfide, potassium selenide, potassium telluride, potassium tetrafluoroaluminate, potassium tetrafluoroborate, potassium tetrahydroborate, potassium methanide, potassium cyanide, potassium formate, potassium hydrogen fluoride, and , potassium iodomercurate(II), potassium hydrogen sulfide, potassium octachlorodimolybdate(II), potassium amide, potassium hydroxide, potassium hexafluorophosphate, potassium carbonate, potassium tetrachloroplatinate(II), potassium hexachloroplatinate(IV), potassium nonahydrido rhenate(VII), potassium sulfate, potassium acetate, potassium cyanaurate(I), potassium hexanitrocobaltate(III), potassium hexacyanoferrate(III), potassium hexacyanoferrate(II), potassium methoxide, Potassium ethoxide, potassium tert-butoxide, potassium cyanate, potassium fulminate, potassium thiocyanate, potassium aluminum sulfate, potassium aluminate, potassium arsenate, potassium bromate, potassium hypochlorite, potassium chlorite, potassium chlorate, potassium perchlorate, potassium carbonate, potassium chromate, potassium dichromate, potassium tetrakis(peroxo)chromate(V), potassium cuprate(III), potassium ferrate, potassium iodate, potassium periodate, potassium permanganate, potassium manganate, potassium hypochlorite The salt may be potassium arginate, potassium molybdate, potassium nitrite, potassium nitrate, tripotassium phosphate, potassium perrhenate, potassium selenate, potassium silicate, potassium sulfite, potassium sulfate, potassium thiosulfate, potassium disulfite, potassium dithionate, potassium disulfate, potassium peroxodisulfate, potassium dihydrogen arsenate, dipotassium hydrogen arsenate, potassium hydrogen carbonate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium hydrogen selenate, potassium hydrogen sulfite, potassium hydrogen sulfate, potassium hydrogen peroxosulfate, or the like.

[0081] <Supplementary Notes> The technical ideas that can be understood from the above-described embodiments and modified examples will be described below. [1] An electronic component comprising: an element body, an inorganic oxide layer covering an outer surface of the element body, and a glass layer covering the outer surface of the inorganic oxide layer, wherein the glass layer contains one or more elements selected from alkali metals and alkaline earth metals, and the concentration of an element identical to the one or more elements selected from alkali metals and alkaline earth metals contained in the glass layer is lower in the inorganic oxide layer than in the glass layer.

[0082] [2] The electronic component according to [1], wherein the inorganic oxide layer has a melting point higher than that of the glass layer. [3] The electronic component according to [1] or [2], wherein the inorganic oxide layer contains one or more specific elements selected from Al, Si, Zr, and Ti.

[0083] [4] The electronic component according to [3], wherein the glass layer contains the same element as the specific element contained in the inorganic oxide layer. [5] The electronic component according to [4], wherein the composition of the concentration of the specific element in the glass layer has a gradient composition in which the concentration decreases with increasing distance from the inorganic oxide layer in the thickness direction of the glass layer.

[0084] [6] The electronic component according to any one of [1] to [5], wherein the average thickness of the inorganic oxide layer is thinner than the average thickness of the glass layer.

[0085] REFERENCE SIGNS LIST 10... Electronic component 20... Element body 30... Inorganic oxide layer 50... Glass layer 41... First internal electrode 42... Second internal electrode 61... First external electrode 62... Second external electrode

Claims

1. An electronic component comprising: an element body; an inorganic oxide layer covering the outer surface of the element body; and a glass layer covering the outer surface of the inorganic oxide layer, wherein the glass layer contains one or more elements selected from alkali metals and alkaline earth metals, and the concentration of an element identical to the one or more elements selected from alkali metals and alkaline earth metals contained in the glass layer in the inorganic oxide layer is lower than the concentration of the identical element in the glass layer.

2. The electronic component according to claim 1, wherein the melting point of the inorganic oxide layer is higher than the melting point of the glass layer.

3. The electronic component according to claim 1 or 2, wherein the inorganic oxide layer contains one or more specific elements selected from Al, Si, Zr, and Ti.

4. The electronic component according to claim 3, wherein the glass layer contains the same type of element as the specific element contained in the inorganic oxide layer.

5. The electronic component according to claim 4, wherein the composition of the concentration of the specific element in the glass layer has a gradient composition in which the concentration decreases with increasing distance from the inorganic oxide layer in the thickness direction of the glass layer.

6. An electronic component according to any one of claims 1 to 5, wherein the inorganic oxide layer has a smaller average thickness than the glass layer.

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