Electronic component

Abstract

This electronic component (10) is provided with an element body (20) and a first base electrode (61A). The first base electrode (61A) has: a surface layer (SL) that includes an outer surface of the first base electrode (61A) and has an average copper concentration of (60) mol% or more; and an intermediate layer iL that is positioned on the element body (20) side with respect to the surface layer (SL) and has an average copper concentration of less than (60) mol%.

Description

Electronic Components

[0001] The present disclosure relates to electronic components.

[0002] The electronic component disclosed in Patent Document 1 has an element body, internal electrodes, and external electrodes. The internal electrodes are located inside the element body. The external electrodes have a base electrode and a metal layer. The base electrode covers a portion of the outer surface of the element body. The base electrode contains copper. The base electrode is electrically connected to the internal electrodes. The metal layer covers the outer surface of the base electrode.

[0003] Patent No. 5206440

[0004] In electronic components such as those disclosed in Patent Document 1, voids that are not filled with copper or resin may exist inside the base electrode. In particular, if many voids exist on the outer surface side of the base electrode, liquids such as plating solutions used when forming a metal layer are likely to penetrate into the inside of the base electrode.

[0005] In order to solve the above-mentioned problems, the present disclosure provides an electronic component comprising a base body and a base electrode covering an outer surface of the base body, wherein the base electrode has a surface layer that includes the outer surface of the base electrode and has an average copper concentration of 60 mol% or more, and an intermediate layer that is located on the base body side of the surface layer and has an average copper concentration of less than 60 mol%.

[0006] Liquid is less likely to penetrate into the base electrode.

[0007] FIG. 1 is a perspective view of an electronic component according to a first embodiment. FIG. 2 is a side view of the electronic component according to the first embodiment. FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 2. FIG. 4 is an enlarged cross-sectional view of a base electrode according to the first embodiment. FIG. 5 is a flowchart of a method for manufacturing an electronic component according to the first embodiment. FIG. 6 is an enlarged cross-sectional view of a base electrode according to a second embodiment.

[0008] Hereinafter, a first embodiment and a second embodiment of the electronic component will be described. Note that the drawings are schematic diagrams for ease of understanding, and components may be enlarged or omitted. Therefore, the dimensional ratios of the components may differ from those of the actual components.

[0009] First Embodiment of Electronic Component (Overall Configuration of Electronic Component) As shown in FIG. 1 , electronic component 10 is a multilayer ceramic capacitor. 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 first axis X is referred to as a second axis Y. An axis perpendicular to first axis X and second axis Y is referred to as a third axis Z. One of the directions along first axis X is referred to as a first positive direction X1, and the direction along first axis X that is opposite to first positive direction X1 is referred to as a first negative direction X2. One of the directions along second axis Y is referred to as a second positive direction Y1, and the direction along second axis Y that is opposite to second positive direction Y1 is referred to as a second negative direction Y2. Furthermore, one of the directions along the third axis Z is defined as a third positive direction Z1, and the direction along the third axis Z opposite to the third positive direction Z1 is defined as a third negative direction Z2.

[0010] The outer surface 21 of the element body 20 has six flat surfaces 22. 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 22 face in different directions. The six flat surfaces 22 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.

[0011] In the outer surface 21 of the element body 20, the boundary portions between two adjacent flat surfaces 22 and the boundary portions between three adjacent flat surfaces 22 are curved. That is, the corners of the element body 20 are rounded and chamfered.

[0012] 1 and 2 , the element body 20 has a dimension along the first axis X that is greater than the dimensions along the second axis Y and the dimensions along the third axis Z. The element body 20 is made of a dielectric ceramic. In the first embodiment, the element body 20 is mainly composed of alumina.

[0013] 3 , the electronic component 10 includes four first internal electrodes 41 and four second internal electrodes 42. The first internal electrodes 41 and the second internal electrodes 42 are embedded inside the element body 20.

[0014] The first internal electrode 41 is made of a conductive material. Specifically, the first internal electrode 41 is made of Ni. The second internal electrode 42 is made of the same material as the first internal electrode 41.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 1, the four first internal electrodes 41 and the four second internal electrodes 42 are all 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 biased toward the first positive direction X1, and the second internal electrodes 42 are biased toward the first negative direction X2.

[0019] 3 , 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. Therefore, the end of the first internal electrode 41 on the first positive direction X1 side is exposed at the first end surface 22A. 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. Therefore, the end of the second internal electrode 42 on the first negative direction X2 side is exposed at the second end surface 22B. 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.

[0020] 3, 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 illustrated by two-dot chain lines.

[0021] The first external electrode 61 covers the first end face 22A and parts of the four side faces 22C of the element body 20 facing in the first positive direction X1. That is, the first external electrode 61 is a five-sided electrode. The first external electrode 61 includes a first base electrode 61A and a first metal layer 61B.

[0022] The first base electrode 61A is laminated on a portion of the outer surface 21 of the element body 20, including the first end face 22A. Specifically, the first base electrode 61A covers the first end face 22A and portions of the four side faces 22C of the element body 20 facing the first positive direction X1. In this embodiment, the first base electrode 61A is made of copper and a polymer compound containing carbon and nitrogen. The compound containing carbon and nitrogen is so-called inorganic carbon or organic carbon. The detailed configuration of the first base electrode 61A will be described later.

[0023] The first metal layer 61B is laminated on the first base electrode 61A. That is, the first metal layer 61B covers the first base electrode 61A from the outside. The first metal layer 61B contains one or more metals selected from copper, nickel, silver, tin, palladium, and gold. In this embodiment, the first metal layer 61B has a Ni plating layer mainly composed of nickel and a Sn plating layer mainly composed of tin. Although not shown, the first metal layer 61B has a structure in which two layers, a Ni plating layer and a Sn plating layer, are laminated in this order from the first base electrode 61A side. Note that "main component" refers to a content ratio of the target substance exceeding 50%. For example, the Ni plating layer of the first metal layer 61B has a nickel content of more than 50 mol%.

[0024] The second external electrode 62 covers the second end face 22B and parts of the four side faces 22C of the element body 20 facing in the second positive direction Y1. That is, the second external electrode 62 is a five-sided electrode. The second external electrode 62 includes a second base electrode 62A and a second metal layer 62B.

[0025] The second base electrode 62A is laminated on a portion of the outer surface 21 of the element body 20, including the second end face 22B. Specifically, the second base electrode 62A 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. That is, the material of the second base electrode 62A is a compound containing copper and carbon as its main components. The average thickness of the second base electrode 62A and the arithmetic mean roughness of the outer surface of the second base electrode 62A are the same as those of the first base electrode 61A.

[0026] The second metal layer 62B is laminated on the second base electrode 62A. That is, the second metal layer 62B covers the second base electrode 62A from the outside. The material of the second metal layer 62B is the same as that of the first metal layer 61B. That is, the second metal layer 62B has a two-layer structure consisting of, in order from the second base electrode 62A side, a Ni-plated layer and a Sn-plated layer.

[0027] 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. Furthermore, 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.

[0028] (Base Electrode) A detailed description will be given below of the configuration of the first base electrode 61A in the first external electrode 61. Note that the configuration of the second base electrode 62A is similar to the configuration of the first base electrode 61A, and therefore description thereof will be omitted.

[0029] 4, the first base electrode 61A is composed of multiple layers. Specifically, the first base electrode 61A is composed of a surface layer SL, an intermediate layer iL, and a base layer BL. The surface layer SL is a layer that includes the outer surface of the first base electrode 61A. When the first base electrode 61A is viewed in cross section in a direction perpendicular to the outer surface 21 of the element body 20, the thickness of the surface layer SL is approximately 10% to 40% of the thickness of the first base electrode 61A.

[0030] The surface layer SL is a sintered body. In other words, the surface layer SL is composed of necked copper, i.e., multiple copper particles that are thickly connected to each other. Therefore, the average copper concentration in the surface layer SL is 60 mol% or more. This average concentration is measured by composition analysis, such as so-called line analysis and point analysis, on the cross section of the first external electrode 61. For example, this average concentration is calculated as the average concentration in a measurement range of 10 nm square in the cross section. Note that in FIG. 4, the shape of the copper particles in the surface layer SL is omitted, and the surface layer SL is illustrated as if it were a layer made of a uniform material.

[0031] The components other than copper in the surface layer SL are mainly a filler 64 and nickel. The filler 64 is a polymer compound containing carbon and nitrogen. The nickel contained in the first base electrode 61A is diffused from the first metal layer 61B to the first base electrode 61A in the plating step S16 described below. However, because copper is necked in the surface layer SL, the range into which nickel is diffused is a range from the outer surface of the surface layer SL to less than half the thickness of the surface layer SL. Specifically, the range into which nickel is diffused is less than 100 nm.

[0032] Furthermore, the arithmetic mean roughness of the outer surface of the surface layer SL is greater than the arithmetic mean roughness of the surface of the surface layer SL facing the element body 20. Specifically, the arithmetic mean roughness of the outer surface of the surface layer SL is 500 nm or greater. The arithmetic mean roughness of the surface layer SL facing the element body 20 is less than 500 nm. Each arithmetic mean roughness is calculated, for example, based on an image of the cut cross section of the electronic component 10 observed with an electron microscope. That is, the arithmetic mean roughness of each surface in the observed image is calculated by image processing.

[0033] The base layer BL is a layer including the contact surface of the first base electrode 61A with the element body 20. The thickness of the base layer BL is approximately 5% to 10% of the thickness of the first base electrode 61A when the first base electrode 61A is viewed in a cross section perpendicular to the outer surface 21 of the element body 20. The average copper concentration in the base layer BL is 30 mol% or more.

[0034] The surface of the base layer BL facing the element body 20 and the surface opposite to the element body 20 are generally flat. Specifically, the arithmetic mean roughness of the surface of the base layer BL facing the element body 20 is smaller than the arithmetic mean roughness of the surface of the surface layer SL facing the element body 20. Although not shown, the base layer BL has a portion integrated with the first internal electrode 41. In other words, the base layer BL is alloyed with the metal of the first internal electrode 41 by interdiffusion.

[0035] The intermediate layer iL is a layer of the first base electrode 61A located closer to the element body 20 than the surface layer SL. The intermediate layer iL has an average copper concentration of 20 mol% or more and less than 60 mol%. The intermediate layer iL contains a plurality of copper particles CP as the copper component. The average particle size of the copper particles CP is 1 nm or more and 100 nm or less. The standard deviation of the particle sizes of the copper particles CP is 10 nm or more. This standard deviation is calculated by randomly selecting 30 or more copper particles CP in a cross-sectional image of the first base electrode 61A.

[0036] The intermediate layer iL has a chain portion 63. In the chain portion 63, a plurality of copper particles CP are continuously connected from the surface of the surface layer SL to the surface of the base layer BL. Furthermore, in the chain portion 63, a plurality of copper particles CP are connected over a length of 100 nm or more in a direction along the outer surface 21 of the element body 20. In this embodiment, substantially the entire copper component of the intermediate layer iL is the chain portion 63.

[0037] Because the chain-like portions 63 of the intermediate layer iL have a spongy structure as a whole, the intermediate layer iL has multiple gaps G as spaces between the chain-like portions 63. That is, the intermediate layer iL has the gaps G as continuous pores. Note that the "gaps G" here refers to portions that are not made of copper. Therefore, the gaps G do not need to be empty spaces when observed as the first base electrode 61A, and may contain substances other than copper. The intermediate layer iL has a filler 64 that fills the gaps G. The material of the filler 64 is the same as described above, that is, a polymer compound containing carbon and nitrogen. In this embodiment, substantially all of the gaps G are filled with the filler 64. Therefore, when the first base electrode 61A is viewed in cross section perpendicular to the outer surface 21 of the element body 20, the filler 64 fills the multiple gaps G. Furthermore, the elastic modulus of the filler 64 is smaller than that of the chain-like portions 63. In other words, the filler 64 is softer than the chain-like portions 63. In addition to the copper being necked in the surface layer SL, the gaps G between the chain-like portions 63 in the intermediate layer iL are filled with filler 64, so that almost no metal components originating from the first metal layer 61B diffuse into the intermediate layer iL.

[0038] In the present embodiment, the volume occupied by copper in the intermediate layer iL is larger than the volume occupied by the filler 64. Specifically, when the first base electrode 61A is viewed in cross section in a direction perpendicular to the outer surface 21 of the element body 20, the ratio of the area occupied by the copper particles CP to the cross-sectional area of ​​the intermediate layer iL is larger than the ratio of the area occupied by the filler 64 to the cross-sectional area of ​​the intermediate layer iL.

[0039] The intermediate layer iL is further divided into a first intermediate layer ML1 and a second intermediate layer ML2. In other words, the intermediate layer iL is composed of a first intermediate layer ML1 and a second intermediate layer ML2, in that order from the surface layer SL side. In this embodiment, each layer is defined by its average copper concentration.

[0040] The first intermediate layer ML1 is a layer located closer to the element body 20 than the surface layer SL. The first intermediate layer ML1 is a layer located between the surface layer SL and the second intermediate layer ML2. The first intermediate layer ML1 has an average copper concentration of 30 mol% or more and less than 60 mol%. The second intermediate layer ML2 is a layer located closer to the element body 20 than the surface layer SL and the first intermediate layer ML1. The second intermediate layer ML2 has an average copper concentration of 20 mol% or more and less than 30 mol%. That is, the average copper concentration in the second intermediate layer ML2 is lower than the average copper concentration in the base layer BL. The average copper concentration in the second intermediate layer ML2 is also lower than the average copper concentration in the first intermediate layer ML1. Therefore, reflecting the difference in the average copper concentrations in the first intermediate layer ML1 and the second intermediate layer ML2, the volumes occupied by the filler 64 in each layer also differ. Specifically, when the first base electrode 61A is viewed in a cross section perpendicular to the outer surface 21 of the element body 20, the proportion of the area occupied by the filler 64 in the cross section of the second intermediate layer ML2 is higher than the proportion of the area occupied by the filler 64 in the cross section of the first intermediate layer ML1. Furthermore, when the first base electrode 61A is viewed in a cross section perpendicular to the outer surface 21 of the element body 20, the total thickness of the first intermediate layer ML1 and the second intermediate layer ML2 is approximately 50% to 80% of the thickness of the first base electrode 61A.

[0041] The total cross-sectional area of ​​the first base electrode 61A, the area occupied by copper, the area occupied by the gap G, and the area occupied by the filler 64 are calculated by image processing. Specifically, first, the element body 20 is ground in a direction perpendicular to the outer surface 21 by focused ion beam processing or the like. Next, a transmission electron microscope (TEM) is used to image the ground cross-section. The imaged range is a range in which the first base electrode 61A is imaged over a distance of 5 μm or more in a direction along the outer surface of the first base electrode 61A. The area of ​​the first base electrode 61A in the image is defined as the "total cross-sectional area." The area occupied by copper in the image range is defined as the "area occupied by copper." The value obtained by subtracting the "area occupied by copper" from the "total cross-sectional area" is defined as the "area occupied by gap G." The area occupied by the filler 64 within the range of the image is defined as the above-mentioned “area occupied by the filler 64.” Note that, in calculating these areas, energy dispersive X-ray spectroscopy (EDX) may be used.

[0042] (Manufacturing Method) Next, a description will be given of a manufacturing method of electronic component 10. As shown in Fig. 5, the manufacturing method of electronic component 10 includes a laminate preparation step S11, an R-chamfering processing step S12, a conductor paste preparation step S13, a conductor application step S14, a curing step S15, and a plating step S16.

[0043] First, in the laminate preparation step S11, a laminate is prepared by stacking and firing ceramic sheets that form the element body 20 and conductive pastes that form the internal electrodes. Specifically, first, multiple ceramic sheets are prepared. Next, the multiple sheets and conductive pastes are alternately stacked. That is, the conductive paste is stacked on the ceramic sheets. Another sheet is stacked on the sheet on which the conductive paste is stacked. Another conductive paste is stacked on the sheet. By stacking the conductive paste a total of eight times in this manner, a laminate of ceramic sheets and conductive paste is produced. Next, the laminate is compressed in the stacking direction using a mold press or the like. The compressed laminate is then cut and shaped to a predetermined size. Next, the laminate is fired, whereby the multiple ceramic sheets become the element body 20 of the electronic component 10. Furthermore, the conductive paste sandwiched between the multiple sheets becomes the first internal electrode 41 and second internal electrode 42 of the electronic component 10. In the laminate preparation step S11, a laminate fired in this manner is prepared. At this stage, the laminate has a rectangular parallelepiped shape.

[0044] 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 22 of the laminate prepared in the laminate preparation process S11 and at the boundary portions between three adjacent flat surfaces 22. For example, the corners of the laminate are R-chamfered by barrel polishing, thereby forming curved surfaces at the boundary portions.

[0045] Next, a conductor paste preparation step S13 is performed. In the conductor paste preparation step S13, a conductor paste is prepared by adding an amine and a carboxylic acid to a copper-containing solution. Specifically, the conductor paste is prepared as a so-called complex ink. First, a copper-containing metal salt is mixed with an amine as a solvent. In this embodiment, the metal salt is powdered copper formate. The amine as a solvent is, for example, a mixture of "2-ethylhexylamine" and "2-amino-methyl-1-propanol." The mixed solution is stirred for approximately 24 hours using a stirrer such as a magnetic stirrer. This causes the powdered copper formate to form a complex and dissolve in the amine. In other words, a copper-containing solution is prepared.

[0046] Next, an amine and a carboxylic acid are added as additives to the solution after stirring. In this embodiment, the amine as the additive is "N,N-diethyl-p-phenylenediamine ((C ２ H ５ ) ２ NC ６ H ４ NH ２ "). Carboxylic acids include hexanoic acid (CH ３ (CH ２ ) ４ The solution containing these additives is then stirred in the same manner as described above. The additives are dispersed in the solution by stirring, producing a conductive paste. In this state, the conductive paste contains particulate copper and a resin component synthesized by the additives.

[0047] Next, the conductor application step S14 is performed. In the conductor application step S14, the conductor paste prepared in the conductor paste preparation step S13 is applied to the element body 20 using a dispenser or the like. The conductor paste is applied to two locations: a portion of the first end face 22A of the element body 20 and a portion of the second end face 22B of the element body 20. Specifically, the conductor paste is applied so as to cover the entire first end face 22A and portions of the four side faces 22C. The conductor paste is also applied so as to cover the entire second end face 22B and portions of the four side faces 22C.

[0048] Next, a curing step S15 is performed. In the curing step S15, the conductive paste is cured to form a first base electrode 61A and a second base electrode 62A on the outer surface 21 of the element body 20. In this embodiment, the element body 20 to which the conductive paste has been applied is heated in a nitrogen atmosphere in which the heating furnace is filled with nitrogen gas, thereby curing the conductive paste. Specifically, the element body 20 to which the conductive paste has been applied is heated at a temperature of 300°C or higher and 1000°C or lower. This causes the conductive paste to be fired.

[0049] Here, the sintering start temperature of the copper contained in the conductor paste is lower than the hardening start temperature of the resin component. Therefore, as the firing temperature increases, sintering of the copper contained in the conductor paste begins first. More specifically, the copper necks from the outer surface side of the conductor paste. That is, the copper particles CP in the conductor paste neck, forming the surface layer SL. Furthermore, because heat is stored in the alumina-based element body 20, necking also progresses in the portion of the conductor paste that contacts the element body 20. That is, the base layer BL is formed. Meanwhile, the temperature of the inner portions of each layer is lower than that of the surface layer SL and the base layer BL. Therefore, necking does not progress as easily in the first intermediate layer ML1 and the second intermediate layer ML2 as in the other layers, and the chain-like portion 63 is formed. Furthermore, differences in temperature and drying speed occur between the base layer BL side and the surface layer SL side of the intermediate layer iL. As a result, the particle size of the copper particles CP that make up the chain-like portion 63 varies. The necking of the copper particles CP is more likely to occur on the first intermediate layer ML1 side than on the second intermediate layer ML2 side. Furthermore, since the surface layer SL side of the intermediate layer iL is at a higher temperature, the resin component located on the surface layer SL side is more likely to decompose. Therefore, the average copper concentration is higher in the first intermediate layer ML1 than in the second intermediate layer ML2.

[0050] At the time when the surface layer SL, the base layer BL, and the chain-like portion 63 are formed, the resin component has not yet begun to harden. That is, the resin component has fluidity. Therefore, the resin component of the conductive paste fills the gaps G, which are the spaces between the chain-like portions 63. Then, when the firing temperature rises to the curing start temperature of the resin component, the resin component begins to harden. In the hardening step S15, the copper component is sintered in this manner to form the chain-like portion 63 made of copper particles CP. Next, the resin component fills the gaps G and then hardens, forming the filler 64 portion of each base electrode. As a result, the first base electrode 61A and the second base electrode 62A described above are formed.

[0051] Next, a plating step S16 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. 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.

[0052] (Regarding Effects of the First Embodiment) Note that, regarding effects common to the first base electrode 61A and the second base electrode 62A, the first base electrode 61A will be described as a representative example, and description of the effects of the second base electrode 62A will be omitted.

[0053] (1-1) In the first embodiment, the average copper concentration in the surface layer SL is higher than the average copper concentration in the intermediate layer iL, which is located closer to the element body 20 than the surface layer SL. In other words, copper necking is advanced in the surface layer SL. When copper is sufficiently necked in this manner, voids are less likely to occur in the surface layer SL. This makes it possible to prevent liquid from adhering to the outer surface of the first base electrode 61A from penetrating into the element body 20.

[0054] (1-2) In the first embodiment, the first base electrode 61A has a base layer BL. In the base layer BL, copper is in a necked state, similar to the surface layer SL. This makes it possible to suppress the intrusion of liquids and the like at the interface between the element body 20 and the first base electrode 61A. Furthermore, the high average concentration of copper makes it difficult for electrical conductivity with the internal electrodes to decrease.

[0055] (1-3) In the first embodiment, the main component of the element body 20 is alumina. Because alumina has a relatively high thermal conductivity, necking tends to progress in the portion of the first base electrode 61A that contacts the element body 20. In other words, the base layer BL tends to be formed.

[0056] (1-4) In the first embodiment, the intermediate layer iL has a chain portion 63. Although the chain portion 63 has a structure in which copper particles CP are connected, the positional relationship of each copper particle CP is not completely constrained. Therefore, even if stress occurs in the first base electrode 61A, the stress can be alleviated by shifting the positions of the copper particles CP. This makes it less likely that cracks will occur in the first base electrode 61A.

[0057] (1-5) In the first embodiment, the average copper concentration in the base layer BL is higher than the average copper concentration in the surface layer SL. This prevents the liquid from penetrating into the first base electrode 61A and reaching the element body 20.

[0058] (1-6) In the first embodiment, the intermediate layer iL has a filler 64 that fills the gaps G of the chain-like portions 63. Because the filler 64 is softer than the chain-like portions 63, even if stress occurs in the first base electrode 61A, the filler 64 is likely to be elastically deformed, thereby alleviating the stress.

[0059] (1-7) In the first embodiment, the average particle size of the copper particles CP is 1 nm or more and 100 nm or less, and the standard deviation of the particle size is 10 nm or more. The variation in particle size of the copper particles CP makes it easy for gaps G to form in the chain-like portion 63, and these gaps G tend to be connected. Therefore, the gaps G are easily filled with the filler 64.

[0060] (1-8) In the first embodiment, the ratio of the area occupied by the copper particles CP to the cross-sectional area of ​​the intermediate layer iL is larger than the ratio of the area occupied by the filler 64 to the cross-sectional area of ​​the intermediate layer iL. This makes it difficult for electrical conduction between the first metal layer 61B and the first internal electrode 41 to be impaired.

[0061] (1-9) In the first embodiment, the proportion of the area occupied by the filler 64 in the cross section of the second intermediate layer ML2 is higher than the proportion of the area occupied by the filler 64 in the cross section of the first intermediate layer ML1. When an external force is applied to the first base electrode 61A, the stress acting on the element body 20 side of the first base electrode 61A tends to be large. This makes it easier to prevent cracks from occurring in the outer surface 21 of the element body 20 or in the base layer BL.

[0062] (1-10) In the first embodiment, the surface layer SL contains nickel. That is, nickel from the first metal layer 61B is diffused into the surface layer SL. As such, there is no clear boundary in terms of the distribution of nickel, and therefore the first metal layer 61B and a portion of the outer surface side of the surface layer SL are in a state of being integrated. As a result, the first metal layer 61B is less likely to peel off from the first base electrode 61A.

[0063] (1-11) In the first embodiment, the arithmetic mean roughness of the outer surface of the surface layer SL is greater than the arithmetic mean roughness of the surface of the surface layer SL facing the element body 20. This creates a so-called anchor effect between the first base electrode 61A and the first metal layer 61B. This increases the adhesive strength between the first base electrode 61A and the first metal layer 61B.

[0064] (1-12) In the first embodiment, the surface layer SL and the base layer BL are necked, so the cross-sectional area of ​​the copper serving as the electron conduction path is large, resulting in a smaller electrical resistance value than when the entire first base electrode 61A is the chain portion 63.

[0065] (1-13) In the first embodiment, the base layer BL is alloyed by interdiffusion with the metal of the first internal electrode 41. This ensures electrical continuity between the first base electrode 61A and the first internal electrode 41. In addition, the first base electrode 61A is less likely to peel off from the element body 20.

[0066] Second Embodiment of Electronic Component Next, a second embodiment of the electronic component will be described. Hereinafter, among the configuration of electronic component 100 according to the second embodiment, the same components as those in the first embodiment will be denoted by the same reference numerals and will not be described again. Furthermore, in the second embodiment, the configuration of the second external electrode is similar to the configuration of first external electrode 161, and therefore will not be described again.

[0067] In the electronic component 100 according to the second embodiment, the material of the element body 120 is different from that of the first embodiment. Specifically, the material of the element body 120 in the second embodiment is barium titanate (BaTiO ３ ) The second embodiment is different from the first embodiment in that the first base electrode 61A does not have a base layer BL.

[0068] 6 , in the first external electrode 161 of the electronic component 100 according to the second embodiment, the first base electrode 161A has a surface layer SL and an intermediate layer iL. The surface layer SL has the same configuration as that described in the first embodiment. However, in the second embodiment, the arithmetic mean roughness of the surface of the surface layer SL facing the element body 120 is greater than the arithmetic mean roughness of the outer surface 21 of the surface layer SL.

[0069] The intermediate layer iL according to the second embodiment is composed of a first intermediate layer ML1 and a second intermediate layer ML2. The configurations of the first intermediate layer ML1 and the second intermediate layer ML2 are the same as those of the first embodiment. Therefore, the intermediate layer iL has a chain portion 63 in which a plurality of copper particles CP are continuously connected from the surface of the surface layer SL to the surface of the element body 120.

[0070] (Effects of the Second Embodiment) According to the second embodiment, in addition to the above effects (1-1), (1-4), (1-6) to (1-11), the following effects can be obtained.

[0071] (2-1) In the second embodiment described above, the material of the element body 120 is barium titanate. Because barium titanate has a lower thermal conductivity than the alumina of the first embodiment, the element body 120 is less likely to retain heat during the curing step S15. This makes it difficult for the base layer BL to form. In other words, a chain-like portion 63 can be formed that extends from the surface layer SL to the element body 120. Because the chain-like portion 63 is larger than when the base layer BL is present, stress on the first external electrode 161 is more easily alleviated.

[0072] (2-2) In the second embodiment, the arithmetic mean roughness of the surface of the surface layer SL facing the element body 120 is greater than the arithmetic mean roughness of the outer surface 21 of the surface layer SL. This increases the contact area between the surface layer SL and the first intermediate layer ML1. This makes the surface layer SL less likely to peel off from the first intermediate layer ML1.

[0073] <Modifications> The first and second embodiments can be modified as follows: Each embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0074] The electronic component 10 is not limited to a multilayer ceramic capacitor. For example, the electronic component 10 may be a piezoelectric component, a thermistor, an inductor, or the like, which includes the element body 20, the first external electrode 61, and the second external electrode 62.

[0075] The material of the element body 120 in the second embodiment is CaTiO ３ , SrTiO ３ , CaZrO ３ The element body 20 of the first embodiment and the element body 120 of the second embodiment may also contain, as a secondary component, a Mn compound, a Co compound, a Si compound, or a compound containing a rare earth element.

[0076] The material of the element 20 may be a dielectric, a piezoelectric, a magnetic material such as ferrite, or a composite of a filler and a metal. The conductive paste may be nanoink. In the case of nanoink, nanometal powder containing copper particles is dispersed in a solvent containing cellosolves, carbitols, hydrocarbons, aromatics, or the like. Then, an amine and a carboxylic acid are added as additives to produce a conductive paste.

[0077] When the conductive paste is a complex ink, the amine and carboxylic acid used as the additive are not limited to those in the above embodiment. Examples of the amine used as the additive include "N,N-dimethyl-1,3-propanediamine," "1,2-propanediamine," "m-xylene-α,α'-diamine," "N,N,N',N'-tetramethyl-p-phenylenediamine," "N,N-dibutyl-1,3-propanediamine," "p-phenylenediamine," "ethylenediamine," "N,N-dimethylethylenediamine," "N,N,N',N'-tetramethylethylenediamine," and "1,4-butanediamine." , "N,N,N',N'-tetramethyl-1,6-hexanediamine," "hexamethylenediamine," "1,5-naphthalenediamine," "1,12-dodecanediamine," "1,8-octanediamine," "o-phenylenediamine," "m-phenylenediamine," "N,N'-dimethylethylenediamine," "4-methyl-1,2-phenylenediamine," "1,3-propanediamine," and "N,N-diethyl-1,3-propanediamine." The carboxylic acid may be, for example, formic acid, acetic acid, propionic acid, butanoic acid, heptanoic acid, valeric acid, octanoic acid, decanoic acid, and the like.

[0078] The number of first internal electrodes 41 and second internal electrodes 42 is not limited to the example in the above embodiment. The number of first internal electrodes 41 may be more or less than four. The same applies to the second internal electrodes 42.

[0079] The intermediate layer iL does not have to have a chain portion 63. It is sufficient that the average copper concentration is within a predetermined range and that the surface layer SL and the first internal electrode 41 are electrically conductive. The material of the filler 64 is not limited to the example in the above embodiment. For example, the filler 64 may be a synthetic resin. Furthermore, the filler 64 does not have to be a polymer compound and may consist only of carbon. Furthermore, the filler 64 does not have to contain carbon or nitrogen. For example, the filler 64 may be a silicone resin.

[0080] The average particle size of the copper particles CP may be less than 1 nm or greater than 100 nm. The standard deviation of the particle size may be less than 10 nm. Even in such a case, the presence of the chain-like portions 63 facilitates stress relaxation.

[0081] The ratio of the area occupied by the copper particles CP to the cross-sectional area of ​​the intermediate layer iL may be equal to or less than the ratio of the area occupied by the filler 64 to the cross-sectional area of ​​the intermediate layer iL. The ratio of the area occupied by the filler 64 in the cross section of the second intermediate layer ML2 may be equal to or less than the ratio of the area occupied by the filler 64 in the cross section of the first intermediate layer ML1. Even in such a case, stress is easily relieved by being filled with the filler 64.

[0082] The intermediate layer iL does not have to have either the first intermediate layer ML1 or the second intermediate layer ML2. For example, the intermediate layer iL may have only the second intermediate layer ML2. It is sufficient that at least the first base electrode 61A is located on the element body 20 side with respect to the surface layer SL and has an intermediate layer iL with an average copper concentration of less than 70 mol%.

[0083] The main component of the first metal layer 61B is not limited to the example in the above embodiment. That is, the first metal layer 61B does not have to include a Ni plating layer containing nickel as the main component. Furthermore, the first external electrode 61 does not have to include the first metal layer 61B.

[0084] In the first embodiment, the arithmetic mean roughness of the outer surface of the surface layer SL may be equal to or less than the arithmetic mean roughness of the surface of the surface layer SL facing the element body 20. In the second embodiment, the arithmetic mean roughness of the surface of the surface layer SL facing the element body 20 may be equal to or less than the arithmetic mean roughness of the outer surface of the surface layer SL. Even in such a case, at least the effects described in (1-1) can be obtained.

[0085] The method for measuring the average metal concentration is not limited to the example of the above embodiment. For example, measurement may be performed using EDX. Specifically, in this method, the element body 20 is first ground in a direction perpendicular to the outer surface 21 using focused ion beam processing or the like. Next, an electron beam is irradiated onto the ground cross section of the element body 20 using a TEM. The electron beam is irradiated over a range of 1 μm or more along the outer surface of the first base electrode 61A. Mapping data of the composition in the cross section is obtained by measuring the dose of characteristic X-rays generated during this process. This 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. That is, in the mapping data, the higher the amount of composition, the higher the brightness 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 brightness values ​​present in that region by the area of ​​that region. In this case, the concentration is expressed as an average brightness value per unit area. In this manner, the average concentration of nickel in the first metal layer 61B and the average concentration of copper in the surface layer SL, etc. The unit of the average concentration may be mole fraction (mol%), mass percent concentration (wt%), etc.

[0086] In the first embodiment, the average copper concentration in the base layer BL may be lower than the average copper concentration in the surface layer SL. In the above embodiment, the necking of copper may be more advanced in the base layer BL than in the surface layer SL. In other words, the average copper concentration in the base layer BL may exceed 60 mol%. Furthermore, the average copper concentration in the base layer BL may be higher than the average copper concentration in the surface layer SL.

[0087] The electronic component 10 may include a glass film. In this case, for example, the glass film may be formed so as to cover a partial region of the outer surface 21 of the element body 20. In other words, even if a glass film covering the element body 20 is present, it is sufficient that the electrical connection between the first internal electrode 41 and the first external electrode 61, and the electrical connection between the second internal electrode 42 and the second external electrode 62 are ensured.

[0088] In the conductor application step S14, the method for applying the conductor paste to the outer surface 21 of the element body 20 is not limited to the example in the above embodiment. For example, the conductor paste may be printed on the outer surface 21 of the element body 20 by a so-called inkjet method, a screen printing method, or the like.

[0089] In the hardening step S15, firing may be performed in multiple stages. For example, when firing is performed in two stages, the element body 20 may first be fired at a temperature of 200° C. to 400° C. for a predetermined time. Next, the element body 20 may be removed from the heating furnace and subjected to a predetermined operation, and then the element body 20 may be fired at a temperature of 300° C. to 1000° C.

[0090] The difference between the sintering start temperature of the copper component of the conductive paste and the hardening start temperature of the filler 64 may vary depending on the material of the filler 64. In order to keep the copper component contained in the conductive paste in a particulate state, it is preferable to use a filler 64 made of a material that ensures the difference in the above-mentioned start temperatures is 100 degrees or less.

[0091] The sintering start temperature of the copper contained in the conductive paste may be equal to or higher than the hardening start temperature of the resin component. The sintering of the copper proceeds in the same process as the hardening of the resin component, so that the filler material 64 can be filled into the gap G.

[0092] <Supplementary Notes> The technical ideas that can be understood from the above embodiments and modifications will be described below. [1] An electronic component comprising an element body and a base electrode covering an outer surface of the element body, the base electrode having a surface layer that includes the outer surface of the base electrode and has an average copper concentration of 60 mol % or more, and an intermediate layer that is located on the element body side of the surface layer and has an average copper concentration of less than 60 mol %.

[0093] [2] An electronic component as described in [1], wherein the average copper concentration of the intermediate layer is less than 60%. [3] The intermediate layer has a first intermediate layer having an average copper concentration of 30 mol% or more but less than 60 mol%, and a second intermediate layer located on the element body side of the first intermediate layer and having an average copper concentration of less than 30 mol%, and the base electrode has a base layer including the contact surface of the base electrode with the element body and having an average copper concentration of 30 mol% or more.

[0094] [4] The electronic component according to [3], wherein the element body is mainly composed of alumina. [5] The electronic component according to [3] or [4], wherein the intermediate layer has a chain-like portion in which a plurality of copper particles are continuously connected from the surface of the surface layer to the surface of the base layer.

[0095] [6] An electronic component according to [5], wherein when the base electrode is viewed in cross section in a direction perpendicular to the outer surface of the body, the average copper concentration in the base layer is higher than the average copper concentration in the surface layer.

[0096] [7] The electronic component according to [5] or [6], wherein the intermediate layer has a filler filled in the spaces between the chain portions. [8] The electronic component according to [7], wherein the copper particles have an average particle size of 1 nm or more and 100 nm or less, and a standard deviation of the particle size is 10 nm or more.

[0097] [9] An electronic component described in [7] or [8], wherein when the base electrode is viewed in cross section in a direction perpendicular to the outer surface of the body, the ratio of the area occupied by the copper particles to the cross-sectional area of ​​the intermediate layer is greater than the ratio of the area occupied by the filler to the cross-sectional area of ​​the intermediate layer.

[0098]

[10] An electronic component described in any one of [7] to [9], wherein when the base electrode is viewed in a cross section perpendicular to the outer surface of the body, the proportion of the area occupied by the filler in the cross section of the second intermediate layer is higher than the proportion of the area occupied by the filler in the cross section of the first intermediate layer.

[0099]

[11] The electronic component according to any one of [3] to

[10] , further comprising a metal layer covering an outer surface of the base electrode, the metal layer containing nickel, and the surface layer containing nickel.

[12] The electronic component according to

[11] , wherein the arithmetic mean roughness of the outer surface of the surface layer is greater than the arithmetic mean roughness of the surface of the surface layer facing the element body.

[0100]

[13] The electronic component according to any one of [1] to [3], wherein the base electrode has a chain-like portion in which a plurality of copper particles are continuously connected from the surface of the surface layer to the surface of the element body.

[14] The electronic component according to

[13] , wherein the element body is mainly composed of barium titanate.

[0101]

[15] An electronic component according to

[13] or

[14] , wherein the arithmetic mean roughness of the surface of the surface layer on the element body side is greater than the arithmetic mean roughness of the outer surface of the surface layer.

[0102] 10... Electronic component 20... Element body 21... Outer surface 61A... First base electrode SL... Surface layer iL... Intermediate layer ML1... First intermediate layer ML2... Second intermediate layer BL... Base layer CP... Copper particle 63... Chain portion 64... Filler G... Gap 61B... First metal layer 62... Second external electrode 62A... Second base electrode 62B...Second metal layer

Claims

1. An electronic component comprising: an element body; and a base electrode covering the outer surface of the element body, wherein the base electrode has: a surface layer that includes the outer surface of the base electrode and has an average copper concentration of 60 mol% or more; and an intermediate layer located on the element body side of the surface layer.

2. The electronic component according to claim 1, wherein the average copper concentration of the intermediate layer is less than 60%.

3. The electronic component according to claim 2, wherein the intermediate layer comprises: a first intermediate layer having an average copper concentration of 30 mol% or more and less than 60 mol%; and a second intermediate layer located on the element body side of the first intermediate layer and having an average copper concentration of less than 30 mol%, and the base electrode has a base layer including a contact surface of the base electrode with the element body and having an average copper concentration of 30 mol% or more.

4. The electronic component according to claim 3, wherein the main component of the element body is alumina.

5. An electronic component according to claim 3 or 4, wherein the intermediate layer has a chain-like portion in which a plurality of copper particles are continuously connected from the surface of the surface layer to the surface of the base layer.

6. The electronic component according to claim 5, wherein, when the base electrode is viewed in cross section in a direction perpendicular to the outer surface of the element body, the average copper concentration in the base layer is higher than the average copper concentration in the surface layer.

7. An electronic component according to claim 5 or 6, wherein the intermediate layer has a filler material filled in the spaces between the chain-like portions.

8. The electronic component according to claim 7, wherein the copper particles have an average particle size of 1 nm or more and 100 nm or less, and the standard deviation of the particle size is 10 nm or more.

9. An electronic component according to claim 7 or 8, wherein, when the base electrode is viewed in cross section in a direction perpendicular to the outer surface of the element body, the ratio of the area occupied by the copper particles to the cross-sectional area of ​​the intermediate layer is greater than the ratio of the area occupied by the filler to the cross-sectional area of ​​the intermediate layer.

10. An electronic component according to any one of claims 7 to 9, wherein, when the base electrode is viewed in cross section in a direction perpendicular to the outer surface of the element body, the proportion of the area occupied by the filler in the cross section of the second intermediate layer is higher than the proportion of the area occupied by the filler in the cross section of the first intermediate layer.

11. The electronic component according to any one of claims 3 to 10, further comprising a metal layer covering an outer surface of the base electrode, the metal layer containing nickel, and the surface layer containing nickel.

12. The electronic component according to claim 11, wherein the arithmetic mean roughness of the outer surface of the surface layer is greater than the arithmetic mean roughness of the surface of the surface layer facing the element body.

13. An electronic component according to any one of claims 1 to 3, wherein the base electrode has a chain-like portion in which a plurality of copper particles are continuously connected from the surface of the surface layer to the surface of the element body.

14. The electronic component according to claim 13, wherein the main component of the element body is barium titanate.

15. An electronic component according to claim 13 or 14, wherein the arithmetic mean roughness of the surface of the surface layer on the element body side is greater than the arithmetic mean roughness of the outer surface of the surface layer.

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