Electronic component

Abstract

This electronic component comprises: an element body (20); and a first external electrode (61) that covers a part of an outer surface (21) of the element body (20). The first external electrode (61) does not contain a silver component. The first external electrode (61) has a first base electrode (61A) that covers the outer surface (21) of the element body (20). The first base electrode (61A) contains copper particles (63) and a silicone (64) as a synthetic resin. If the first base electrode (61A) is divided into equal halves, specifically into a first portion (P1) that is positioned on the element body (20) side and a second portion (P2) that is positioned on the opposite side from the element body (20), the average value of the particle diameters of the copper particles (63) in the second portion (P2) is greater than the average value of the particle diameters of the copper particles (63) in the first portion (P1).

Description

[Technical Field]

[0001] The present disclosure relates to electronic components. [Background technology]

[0002] The electronic component described 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 include a first electrode, a second electrode, and a third electrode. The first electrode covers a portion of the outer surface of the element body. The first electrode is mainly composed of Cu. The second electrode covers the outer surface of the first electrode. The second electrode is mainly composed of Ag-Pd. The third electrode covers the outer surface of the second electrode. The third electrode is mainly composed of Ag and a synthetic resin. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-229077 Summary of the Invention [Problem to be solved by the invention]

[0004] The electronic component described in Patent Document 1 is subject to external mechanical shock or thermal shock due to temperature change. This can cause cracks or other damage to the element body of the electronic component. In the electronic component described in Patent Document 1, the third electrode contains a synthetic resin, and the resin component can suppress impacts to the element body. However, the silver component of the third electrode is prone to elution in high-temperature, high-humidity environments. Therefore, the eluted silver component may come into contact with the element body and cause migration. Therefore, a technology is needed that can suppress impacts to the element body while suppressing migration. [Means for solving the problem]

[0005] To solve the above problems, one aspect of the present disclosure provides an electronic component including a base body and an external electrode covering a part of the outer surface of the base body and not containing a silver component. The external electrode has an underlayer electrode covering the outer surface of the base body. The underlayer electrode contains copper particles and a synthetic resin. When the underlayer electrode is bisected into a first portion located on the base body side and a second portion located on the side opposite to the base body, the average value of the particle size of the copper particles in the second portion is larger than the average value of the particle size of the copper particles in the first portion.

Advantages of the Invention

[0006] In the above configuration, the external electrode does not contain a silver component. Therefore, according to the above configuration, migration can be suppressed as compared with the case where the external electrode contains a silver component. On the other hand, since the particle size of the copper particles in the second portion is relatively large, it is also possible to suppress the occurrence of cracks or the like in the base body.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0008] <One Embodiment of the Electronic Component> Hereinafter, an embodiment of an electronic component will be described with reference to the drawings. Note that the drawings may show the components enlarged for ease of understanding. The dimensional ratios of the components may be different from the actual ones or those in other drawings.

[0009] <Regarding the electronic component> As shown in FIG. 1, the electronic component 10 is a multilayer ceramic capacitor. The electronic component 10 includes a body 20. The body 20 is substantially quadrangular prism-shaped and has a central axis CA. Hereinafter, the axis extending along the central axis CA is defined as the first axis X. Also, one of the axes orthogonal to the first axis X is defined as the second axis Y. And the axis orthogonal to the first axis X and the second axis Y is defined as the third axis Z. In addition, one of the directions along the first axis X is defined as the first positive direction X1, and the direction opposite to the first positive direction X1 among the directions along the first axis X is defined as the first negative direction X2. Also, one of the directions along the second axis Y is defined as the second positive direction Y1, and the direction opposite to the second positive direction Y1 among the directions along the second axis Y is defined as the second negative direction Y2. Further, one of the directions along the third axis Z is defined as the third positive direction Z1, and the direction opposite to the third positive direction Z1 among the directions along the third axis Z is defined as the third negative direction Z2.

[0010] The outer surface 21 of the body 20 has six planes. Here, the "plane" of the body 20 refers to what can be observed as a plane when observing the entire body 20. That is, for example, even if there are minute irregularities or steps that cannot be known without magnifying a part of the body 20 with a microscope or the like, it is expressed as a plane or a curved surface. The six planes face different directions. The six planes are roughly classified into a first end face 22A facing the first positive direction X1, a second end face 22B facing the first negative direction X2, and four side faces 22C. Each of the four side faces 22C is a face facing the third positive direction Z1, a face facing the third negative direction Z2, a face facing the second positive direction Y1, and a face facing the second negative direction Y2.

[0011] Among the outer surface 21 of the body 20, the boundary portions between two adjacent planes and the boundary portions between three adjacent planes are curved surfaces. That is, the corners of the body 20 have an R chamfered shape.

[0012] As shown in FIGS. 1 and 2, the base body 20 has a dimension in the direction along the first axis X that is larger than the dimensions in the directions along the third axis Z and the second axis Y. The material of the base body 20 is a dielectric ceramic. Specifically, the material of the base body 20 is mainly composed of BaTiO3. Also, the material of the base body 20 may be mainly composed of CaTiO3, SrTiO3, CaZrO3, etc. Further, the material of the base body 20 may contain, as secondary components, Mn compounds, Co compounds, Si compounds, rare earth compounds, etc.

[0013] As shown in FIG. 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 located inside the base body 20.

[0014] The material of the first internal electrode 41 is a conductive material. For example, the material of the first internal electrode 41 is Ni. Also, the material of the first internal electrode 41 may further contain metals such as Ni, Cu, Ag, Au, Pt, Sn, Pd, or alloys containing these metals. The material of the second internal electrode 42 is the same as the material of the first internal electrode 41.

[0015] The shape of the first internal electrode 41 is a rectangular plate shape. The main surface of the first internal electrode 41 is orthogonal to the second axis Y. The shape of the second internal electrode 42 is the same rectangular plate shape as the first internal electrode 41. The main surface of the second internal electrode 42 is orthogonal 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 base 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 base body 20 in the direction along the third axis Z. The dimensions of the second internal electrode 42 in each direction are the same as those of the first internal electrode 41.

[0017] As shown in FIG. 3, the first internal electrode 41 and the second internal electrode 42 are alternately positioned in the direction along the second axis Y. That is, a total of eight internal electrodes are arranged alternately in the order of the first internal electrode 41 and the second internal electrode 42 from the side surface 22C facing the second positive direction Y1 toward the second negative direction Y2. In this embodiment, the distances in the direction along the second axis Y between the respective internal electrodes are equal.

[0018] As shown in FIG. 1, all of the four first internal electrodes 41 and the four second internal electrodes 42 are positioned 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 electrode 41 is positioned closer to the first positive direction X1. The second internal electrode 42 is positioned closer to the first negative direction X2. Specifically, the end of the first internal electrode 41 on the first positive direction X1 side substantially 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 from the first end surface 22A of the element body 20. The end of the first internal electrode 41 on the first negative direction X2 side is positioned inside the element body 20 and does not reach the end of the element body 20 on the first negative direction X2 side.

[0019] On the other hand, the end of the second internal electrode 42 on the first negative direction X2 side substantially 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 from the second end surface 22B of the element body 20. The end of the second internal electrode 42 on the first positive direction X1 side is positioned inside the element body 20 and does not reach the end of the element body 20 on the first positive direction X1 side.

[0020] As shown in FIG. 3, the electronic component 10 includes a first external electrode 61 and a second external electrode 62. The first external electrode 61 and the second external electrode 62 are conductive as a whole. On the other hand, the first external electrode 61 and the second external electrode 62 do not contain a silver component. Here, "not containing a silver component" means that a slight amount of silver component mixed into each external electrode during the manufacturing process is allowed. For example, if the atomic percentage of silver atoms with respect to all atoms constituting each external electrode is less than 1 atm%, it is regarded that "the external electrode does not contain a silver component". This is because if the atomic percentage of silver atoms is less than 1 atm%, no significant migration that affects the characteristics of the electronic component 10 occurs.

[0021] The first external electrode 61 has a first base electrode 61A, a first mixed layer 61B, and a first metal layer 61C. In FIG. 3, the first mixed layer 61B is shown by a thick line. The first base electrode 61A covers a part of the outer surface 21 of the body 20 including the first end face 22A. The first base electrode 61A is a five-sided electrode that covers the first end face 22A of the body 20 and a part of the four side faces 22C on the first positive direction X1 side. In this embodiment, the material of the first base electrode 61A is copper and glass. Also, the first base electrode 61A is a sintered body. Details of the first base electrode 61A will be described later.

[0022] The first metal layer 61C covers the outer surface BD61A of the first base electrode 61A. Also, a part of the first metal layer 61C protrudes from the first base electrode 61A. Although not shown, the first metal layer 61C has a two-layer structure of a nickel layer and a tin layer in order from the first mixed layer 61B side.

[0023] The first mixed layer 61B is located between the first base electrode 61A and the first metal layer 61C. In other words, the above-mentioned first metal layer 61C covers the outer surface BD61A of the first base electrode 61A via the first mixed layer 61B. Details of this first mixed layer 61B will be described later.

[0024] The second external electrode 62 has a second base electrode 62A, a second mixed layer 62B, and a second metal layer 62C. In FIG. 3, the second mixed layer 62B is shown by a thick line. The second base electrode 62A covers a part of the outer surface 21 of the element body 20 including the second end face 22B. The second base electrode 62A is a five-sided electrode that covers the second end face 22B of the element body 20 and a part of the first negative direction X2 side of the four side faces 22C. In this embodiment, the material of the second base electrode 62A is the same as that of the first external electrode 61, which is copper and glass. Also, the second base electrode 62A is a sintered body like the first base electrode 61A. Details of the second base electrode 62A will be described later.

[0025] The second metal layer 62C covers the outer surface BD62A of the second base electrode 62A. Also, a part of the second metal layer 62C protrudes from the second base electrode 62A. Although not shown, the second metal layer 62C has a two-layer structure of a nickel layer and a tin layer in order from the second mixed layer 62B side, similar to the first metal layer 61C.

[0026] The second mixed layer 62B is located between the second base electrode 62A and the second metal layer 62C. In other words, the above-mentioned second metal layer 62C covers the outer surface BD62A of the second base electrode 62A via the second mixed layer 62B. Details of this second mixed layer 62B will be described later.

[0027] On the side face 22C, the second external electrode 62 does not reach the first external electrode 61 and is arranged apart from the first external electrode 61 in the direction along the first axis X. And on the side face 22C of the element body 20, the central portion in the direction along the first axis X is not laminated with the first external electrode 61 and the second external electrode 62. In FIGS. 1 to 3, the first external electrode 61 and the second external electrode 62 are shown by a two-dot chain line.

[0028] <Configuration of the First Base Electrode and the Second Base Electrode> Hereinafter, the first base electrode 61A will be described as a representative, but the same applies to the second base electrode 62A. The first base electrode 61A contains copper and silicon.

[0029] As shown in FIG. 5, at least a part of the copper in the first base electrode 61A is spherical copper particles 63. In FIG. 5, only some of the copper particles 63 are labeled. Also, in FIG. 5, each copper particle 63 is illustrated as being substantially circular, but it may be elliptical or other irregularly shaped particles.

[0030] Also, the silicon in the first base electrode 61A exists as a silicone resin 64. The silicone resin 64 is a polymer composed of a siloxane bond and an Si-C bond.

[0031] As shown in FIG. 4, the average value of the thickness H of the first base electrode 61A is about 700 nm. The thickness H of the first base electrode 61A is the shortest distance from the outer surface BD61A of the first base electrode 61A to the outer surface 21 of the element body 20. In FIG. 4, the thickness H at an arbitrary location is illustrated. Also, in FIG. 4, the illustration of the copper particles 63 and the silicone resin 64 in the first base electrode 61A is omitted, and the first base electrode 61A is illustrated as an integral body. The average value of the thickness H of the first base electrode 61A is calculated as follows. First, an arbitrary cross-section of the first base electrode 61A is photographed with an electron microscope. Next, for the photographed image, a range in the direction along the outer surface BD61A of the first base electrode 61A is specified. In this range, for a measurement range of at least 5 μm or more, the cross-sectional area of the first base electrode 61A is calculated by image processing. Then, the cross-sectional area of the first base electrode 61A in the calculated measurement range is divided by the length of the measurement range to calculate the average value of the thickness H of the first base electrode 61A. The outer surface BD61A of the first base electrode 61A is defined as the boundary where no chemical components contained only in the first metal layer 61C are observed. The outer surface BD61A of the first base electrode 61A substantially coincides with the interface following the edge of the copper particles 63 on the first metal layer 61C side in the above cross-section.

[0032] Here, assume that the first underlying electrode 61A is bisected into a first portion P1 located on the element body 20 side of the first underlying electrode 61A and a second portion P2 located on the side opposite to the element body 20. The position bisecting the first underlying electrode 61A is a location that bisects the average value of the thickness H of the first underlying electrode 61A. In the present embodiment, the first portion P1 is in the range of about 350 nm from the outer surface 21 of the element body 20 toward the outer surface BD61A side of the first underlying electrode 61A.

[0033] The first underlying electrode 61A has voids PA in which a synthetic resin such as silicone resin 64 does not exist between the copper particles 63. The ratio of the voids PA in the second portion P2 is larger than the ratio of the voids PA in the first portion P1. In particular, in the entire first underlying electrode 61A, the voids PA are more numerous in the vicinity of the outer surface BD61A of the first underlying electrode 61A. In FIG. 4, the voids PA are schematically illustrated.

[0034] Note that the ratio of the voids PA in the second portion P2 and the ratio of the voids PA in the first portion P1 use the porosity measured as follows. First, in a transmission electron microscope, the first portion P1 is observed in a square range with a side length of 500 nm at a magnification of 200,000 times or more. In the said range, the total area of the locations without the copper particles 63 and the silicone resin 64, that is, the voids PA, is calculated by image processing. Then, the porosity is calculated from the area ratio between the total area of the voids PA and the observation range. This process is repeated at four locations of the first portion P1, and the average value of the porosity of each range is taken as the ratio of the voids PA in the first portion P1. Similarly, the ratio of the voids PA in the second portion P2 is calculated.

[0035] As shown in FIG. 5, the average value of the particle size of the copper particles 63 is different between the first portion P1 and the second portion P2. Specifically, the average value of the particle size of the copper particles 63 in the first portion P1 is smaller than the average value of the particle size of the copper particles 63 in the second portion P2. Specifically, the average value of the particle size of the first portion P1 is 75 nm or less. Also, the average value of the particle size of the second portion P2 is 100 nm or more. Therefore, the ratio of the average value of the particle size of the copper particles 63 in the second portion P2 to the average value of the particle size of the copper particles 63 in the first portion P1 is 1.2 or more. Also, as a whole of the first underlying electrode 61A, the particle size of the copper particles 63 becomes smaller as it goes toward the base body 20 side within the first underlying electrode 61A.

[0036] The average value of the particle size of the copper particles 63 in the first portion P1 is determined as follows. First, an image of the first underlying electrode 61A is acquired at a magnification of a range including the outer surface BD61A of the first underlying electrode 61A and the boundary with the outer surface 21 side of the base body 20 by an electron microscope. Then, in the image, the first portion P1 of a location not including the boundary with the outer surface 21 of the base body 20 and the position bisecting the first underlying electrode 61A is enlarged, and the contour of the copper particles 63 is acquired by image processing. Then, the area of one copper particle 63 is calculated. Then, a circle having the calculated area is assumed. The diameter of the circle is calculated as the particle size of the copper particles 63. Then, the particle sizes are calculated for five or more copper particles 63, and the average value thereof is calculated. In this way, the average value of the particle size of the copper particles 63 is calculated in five or more images, and the average value of the average values obtained from these five images is taken as the average value of the particle size of the copper particles 63 in the first portion P1. Similarly, the average value of the particle size of the copper particles 63 in the second portion P2 is calculated.

[0037] As shown in FIG. 6, here, it is assumed that a cross-sectional view is taken in a specific cross-section orthogonal to the outer surface BD61A of the first underlying electrode 61A. In the specific cross-section, at least a part of the copper particles 63 has an elliptical shape. In FIG. 6, reference numerals are attached only to some of the copper particles 63.

[0038] In a specific cross-section, the flatness ratio of the elliptical copper particles 63 is 0.5 or less. The flatness ratio is calculated as follows. First, the contour of the copper particles 63 is obtained by image processing using an electron microscope. The obtained image is analyzed, and among the line segments connecting the edges of one copper particle 63, the length of half of the longest line segment is defined as the major radius. Also, the length of half of the line segment connecting the edges of the copper particle 63 and orthogonal to the major radius is defined as the minor radius. When the major radius is a, the minor radius is b, and the flatness ratio is F, the flatness ratio is calculated based on the following formula (1). (Formula 1) F = 1 - (b / a) Also, in the elliptical copper particles 63, the axis along the major radius is defined as the major axis V1. And the axis along the minor radius is defined as the minor axis V2 of the copper particle 63. The acute angle Q formed by the major axis V1 of the elliptical copper particles 63 in the specific cross-section and the axis L along the outer surface BD61A of the first base electrode 61A is 45 degrees or less. That is, the elliptical copper particles 63 are positioned in such a posture that the major axis V1 as a whole is along the outer surface BD61A of the first base electrode 61A. The axis L along the outer surface BD61A of the first base electrode 61A is determined as follows. For the image obtained in the above specific cross-section, an approximate straight line with respect to the outer surface BD61A of the first base electrode 61A is drawn. The approximate straight line can be obtained, for example, by the least squares method. And the axis along this approximate straight line is defined as the axis L along the outer surface BD61A of the first base electrode 61A.

[0039] [[ID=,5]] <Regarding the mixed layer> The first mixed layer 61B and the second mixed layer 62B will be described. Hereinafter, the first mixed layer 61B will be described as a representative, but the same applies to the second mixed layer 62B.

[0040] As shown in FIG. 4, the first mixed layer 61B is located between the first base electrode 61A and the first metal layer 61C. Although the boundaries of the first base electrode 61A, the first mixed layer 61B, and the first metal layer 61C are virtually illustrated by solid lines, there may be cases where clear boundaries cannot be observed.

[0041] The first mixed layer 61B is sufficiently thinner than the thickness H of the first base electrode 61A. For example, the thickness of the first mixed layer 61B is 10% or less of the thickness H of the first base electrode 61A. The first mixed layer 61B does not contain components included in the first base electrode 61A and contains chemical components included in the first metal layer 61C. Specifically, the chemical component is a nickel component which is a constituent component of the first metal layer 61C. Further, the first mixed layer 61B does not contain components included in the first metal layer 61C and contains chemical components included in the first base electrode 61A. Specifically, the chemical components are a copper component and a silicone component which are constituent components of the first base electrode 61A. Further, in the present embodiment, the constituent components of the first mixed layer 61B do not include components other than the constituent components of the first base electrode 61A and the constituent components of the first metal layer 61C. That is, the first mixed layer 61B is a layer formed by mixing the first base electrode 61A and the first metal layer 61C.

[0042] <Method for manufacturing electronic component> Next, a method for manufacturing the electronic component 10 will be described. As shown in FIG. 7, the method for manufacturing the electronic component 10 includes a laminate preparation step S11, an R chamfering step S12, a conductor coating step S13, a curing step S14, and a plating step S15.

[0043] First, in order to form the body 20, in the laminate preparation step S11, a laminate is prepared. Since the laminate at this stage is in a state before R chamfering, it has a rectangular parallelepiped shape having six planes. Specifically, for example, a plurality of ceramic sheets that will become the body 20 are prepared. The sheet is in a thin plate shape. A conductive paste that will become the first internal electrode 41 is laminated on the sheet. A ceramic sheet that will become the body 20 is laminated on the 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 alternately. Then, the laminated sheets are crimped in the lamination direction by means such as die pressing. Thereafter, the crimped product is cut to a predetermined size to form an unfired laminate. Thereafter, the unfired laminate is fired at a high temperature to prepare a laminate.

[0044] Next, an R chamfering process S12 is performed. In the R chamfering process S12, R chamfering is performed on the laminate prepared in the laminate preparation process S11. By this process, a blank 20 with R chamfered corners is obtained.

[0045] Next, a conductor coating process S13 is performed. In the conductor coating process S13, a conductor paste is applied by an immersion method to two locations, namely, a part of the first end face 22A of the blank 20 and a part of the second end face 22B of the blank 20. Specifically, the conductor paste is applied so as to cover the entire first end face 22A and a part on the four side faces 22C. Also, the conductor paste is applied so as to cover the entire second end face 22B and a part on the four side faces 22C. The conductor paste contains a copper component and a silicon component.

[0046] Note that the conductor paste is a complex ink. And the conductor paste of the complex ink is prepared as follows. First, an amine compound such as 2-ethylhexylamine and an alcohol amine such as 2-amino-2-methylpropanol are mixed. Then, a silicon component such as a silicone resin is added in an amount of 0.001 - 10 wt% based on the weight of Cu alone. Then, a metal salt is further added and dissolved to prepare the conductor paste. That is, the conductor paste contains a copper component and a silicon component. The sintering start temperature of the copper component is 170 degrees, and the curing start temperature of the silicon component is 250 degrees.

[0047] Next, a curing process S14 is performed. Specifically, in the curing process S14, the blank 20 coated with the conductor paste is heated. In this embodiment, the blank 20 coated with the conductor paste is heated in a nitrogen atmosphere. Note that in the curing process S14, the heating is performed in two steps. The first step is to maintain the temperature of the nitrogen atmosphere within the range of 200 degrees to 400 degrees. The second step is to maintain the temperature of the nitrogen atmosphere within the range of 300 degrees to 700 degrees. Thereby, the conductor paste is fired. Note that due to the heating in the second step, the bonds of some chemical components in the synthetic resin contained in the conductor paste are decomposed, and voids PA are generated.

[0048] Also, during the firing of the conductive paste, copper particles 63 and silicone resin 64 are formed as follows. First, the sintering of the copper component contained in the first base electrode 61A and the second base electrode 62A is started. At the time when the sintering of the copper component starts, the silicon component has not hardened and has fluidity. Therefore, the silicon component is filled in the gaps between the copper components. Also, during the sintering of the copper component, the sintering of the copper component starts from the surface side of the conductive paste. At this time, small copper particles 63 are united into large copper particles 63 by Ostwald ripening. As a result, the average value of the particle diameter of the copper particles 63 in the second portion P2 becomes larger than the average value of the particle diameter of the copper particles 63 in the first portion P1.

[0049] After the sintering of the copper component starts, when the temperature further rises to the curing start temperature of the silicon component, the curing of the silicon component contained in the first base electrode 61A and the second base electrode 62A starts. That is, the curing start temperature of the silicon component is higher than the sintering start temperature of the copper component. And when the copper component is sintered, copper particles 63 are generated. Also, when the silicon component is cured, silicone resin 64 is generated. Also, as described above, since the curing start temperature of the silicon component is higher than the sintering start temperature of the copper component, it becomes a network-like silicone resin 64 that fills the gaps between the copper particles 63. As a result, the first base electrode 61A and the second base electrode 62A as described above are formed.

[0050] Next, the plating process S15 is performed. Electroplating is performed on the portions of the first base electrode 61A and the second base electrode 62A. Thereby, a first metal layer 61C is formed on the surface of the first base electrode 61A. Also, a second metal layer 62C is formed on the surface of the second base electrode 62A. In the plating process S15, a part of the chemical composition of the first metal layer 61C is mixed with the melted chemical composition from the first base electrode 61A, thereby forming a first mixed layer 61B. The same applies to the second mixed layer 62B. Although not shown, the first metal layer 61C and the second metal layer 62C are electroplated with two types of nickel and tin to form a two-layer structure. In this way, the electronic component 10 is formed.

[0051] <Effects of the present embodiment> The effects of the present embodiment will be described. In the following, the effects related to the first external electrode 61 will be described as a representative, but the same effects are also exhibited in the second external electrode 62.

[0052] (1) In the above embodiment, the first external electrode 61 does not contain a silver component. Therefore, according to the above embodiment, migration can be suppressed as compared with the case where the first external electrode 61 contains a silver component.

[0053] Also, in the above embodiment, the average value of the particle diameters of the copper particles 63 in the second portion P2 is larger than the average value of the particle diameters of the copper particles 63 in the first portion P1. Since the particle diameter of the copper particles 63 in the second portion P2 is large, the number of copper particles 63 contained in the second portion P2 is smaller than that in the first portion P1. Therefore, in the second portion P2, the contact area of one copper particle 63 with other copper particles 63 is smaller than that in the first portion P1. As a result, the mechanical strength of the second portion P2 is lower than that of the first portion P1. Therefore, if the electronic component 10 is subjected to an impact, cracks are more likely to occur in the second portion P2 than in the first portion P1. That is, the second portion P2 plays a role of mitigating the influence of the impact by itself being damaged. Therefore, when an impact acts on the electronic component 10, since the second portion P2 absorbs the impact, cracks and the like are less likely to occur in the element body 20. Furthermore, since the above-described impact mitigation effect can be exhibited in the second portion P2 on the side far from the element body 20 in the first base electrode 61A, the impact is less likely to affect the element body 20. That is, according to the above embodiment, it is possible to suppress the occurrence of migration and suppress the impact on the element body 20.

[0054] (2) In the above embodiment, the ratio of the average value of the particle diameters of the copper particles 63 in the second portion P2 to the average value of the particle diameters of the copper particles 63 in the first portion P1 is 1.2 or more. According to this configuration, the impact mitigation effect in the second portion P2 is more likely to be exhibited.

[0055] (3) In the above-described embodiment, the average value of the particle size of the copper particles 63 in the second portion P2 is 100 nm or more. According to this configuration, since the average value of the copper particles 63 in the second portion P2 is relatively large, the contact area between the copper particles 63 is reduced. That is, by deliberately reducing the mechanical strength of the second portion P2, the shock mitigation effect on the base body 20 can be further improved.

[0056] (4) In the above-described embodiment, the average value of the particle size of the copper particles 63 in the first portion P1 is 75 nm or less. In this configuration, since the average value of the copper particles 63 in the first portion P1 is relatively small, the contact area between the copper particles 63 is increased. That is, according to the above configuration, by ensuring the mechanical strength of the first portion P1, it is possible to suppress the crack generated in the second portion P2 from propagating to the entire first base electrode 61A including the first portion P1.

[0057] (5) In the above-described embodiment, the acute angle Q formed by the major axis V1 of the elliptical copper particles 63 and the axis L along the outer surface BD61A of the first base electrode 61A in a specific cross-section is 45 degrees or less. That is, the copper particles 63 are in a posture such that they are horizontally long in the direction along the outer surface BD61A of the first base electrode 61A. Cracks are likely to occur in the gaps between the copper particles 63. Therefore, if a crack occurs in the second portion P2, there is a high possibility that the crack will extend in the direction along the outer surface BD61A of the first base electrode 61A. Therefore, according to the above configuration, even if a crack occurs in the second portion P2, the possibility of the crack propagating to the first portion P1 is small.

[0058] (6) In the above-described embodiment, the ratio of the void PA in the second portion P2 is larger than the ratio of the void PA in the first portion P1. If an impact acts on the first base electrode 61A, cracks are likely to occur starting from the void PA. Therefore, according to the above configuration, the possibility of cracks occurring in the second portion P2 is higher than that in the first portion P1. As a result, the shock mitigation effect by the second portion P2 can be surely obtained.

[0059] (7) In the above embodiment, the first mixed layer 61B does not contain the chemical components included in the first base electrode 61A, but contains the chemical components included in the first metal layer 61C. Further, the first mixed layer 61B does not contain the chemical components included in the first metal layer 61C, but contains the chemical components included in the first base electrode 61A. In other words, in the vicinity of the boundary between the first base electrode 61A and the first metal layer 61C, there is a first mixed layer 61B in which the chemical components of each other are mixed. According to such a configuration, since the first base electrode 61A has a structure in which it is partially integrated with the first metal layer 61C, the first metal layer 61C is difficult to be peeled off from the first base electrode 61A.

[0060] <Modified Example> The above embodiment and the following modified examples can be implemented in combination with each other as long as they do not technically conflict with each other. In the case of a modified example that can be commonly applied to the first external electrode 61 and the second external electrode 62, the modified example regarding the first external electrode 61 will be described as a representative.

[0061] · In the above embodiment, 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. · In the above embodiment, the material of the element body 20 may be a dielectric, a piezoelectric, a magnetic material such as ferrite, or a composite body of a synthetic resin and a metal.

[0062] · The shape of the element body 20 is not limited to the example of the above embodiment. For example, the element body 20 may be a polygonal column other than a quadrangular column having a central axis CA. Further, the element body 20 may be a core of a wound-type 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 both ends of the winding core portion.

[0063] · Among the outer surfaces 21 of the element body 20, the boundary portions between adjacent planes do not have to be chamfered. In this case, there is no curved surface at the boundary portion. · The shapes of the first internal electrode 41 and the second internal electrode 42 may be any shape as long as electrical conduction with the corresponding first external electrode 61 and second external electrode 62 can be ensured. Also, the number of the first internal electrode 41 and the second internal electrode 42 is not limited, and may be less than four or more than four.

[0064] · In the above embodiment, the first external electrode 61 may not have the first mixed layer 61B. That is, the boundary between the first base electrode 61A and the first metal layer 61C may be clearly distinguishable. Also, in a configuration without the first mixed layer 61B, the first metal layer 61C only needs to cover at least a part of the first base electrode 61A.

[0065] · In the above embodiment, the average value of the thickness H of the first base electrode 61A is not limited to the example of the above embodiment. Considering the mechanical strength required for the electronic component 10 and the like, the overall thickness of the first external electrode 61 including the first base electrode 61A may be designed.

[0066] · In the above embodiment, the configuration regarding the first metal layer 61C in the first external electrode 61 may be omitted. Also, the material of the first metal layer 61C is not limited to the example of the above embodiment. For example, the first metal layer 61C may be only nickel, may be only tin, or may contain other materials other than silver. For example, the first metal layer 61C may be copper, gold, palladium, or the like.

[0067] · In the above embodiment, the synthetic resin is not limited to the silicone resin 64. For example, the synthetic resin may be a synthetic resin containing silicon such as a silicone oligomer. Thus, when the synthetic resin contains silicon, the first base electrode 61A is likely to become a dense film. Also, the synthetic resin contained in the first base electrode 61A may contain nitrogen. For example, the synthetic resin may be a synthetic resin containing nitrogen such as urethane, epoxy, polyimide, polyimide amide, or polyamide. Thus, when the synthetic resin contains nitrogen, the heat resistance of the first base electrode 61A is improved.

[0068] Further, the synthetic resin is not limited to a resin containing nitrogen and silicon, and may be a resin such as acrylic, alkyd, or polyester, or other synthetic resins may be employed. Further, the first base electrode 61A may employ, as the synthetic resin, a composite of these synthetic resins containing nitrogen, synthetic resins containing silicon, and other synthetic resins. The first base electrode 61A may employ, as the synthetic resin, a material containing silicon and nitrogen in one type of synthetic resin.

[0069] ·In the above embodiment, the average value of the particle size of the copper particles 63 in the first portion P1 may be larger than 75 nm. Further, the average value of the particle size of the copper particles 63 in the second portion P2 may be smaller than 100 nm. Further, the ratio of the average value of the particle size of the copper particles 63 in the second portion P2 to the average value of the particle size of the copper particles 63 in the first portion P1 may be less than 1.2. In order to more effectively obtain the effect described in the above (2), the ratio of the average value of the particle size of the copper particles 63 in the second portion P2 to the average value of the particle size of the copper particles 63 in the first portion P1 is preferably 1.4 or more, and more preferably 1.6 or more.

[0070] ·In the above embodiment, the acute angle Q formed by the major axis V1 of the copper particles 63 and the axis L along the outer surface BD61A of the first base electrode 61A may be larger than 45 degrees. In the above embodiment, the flatness ratio of the copper particles 63 may be larger than 0.5. Further, in a specific cross-section, all of the copper particles 63 may be substantially circular.

[0071] ·In the above embodiment, the ratio of the void PA in the second portion P2 may be the same as or smaller than the ratio of the void PA in the first portion P1. Further, in the above embodiment, the first base electrode 61A may not have the void PA.

[0072] ·The manufacturing process of the electronic component 10 in the above embodiment is not limited to the example of the above embodiment. For example, a process such as physical polishing may be performed on the element body 20. ·In the above-described embodiment, the method of applying the conductor paste is not limited to the example of the above-described embodiment. For example, these pastes may be applied by printing, or may be applied by an inkjet method or the like.

[0073] ·In the curing step S14 of the above-described embodiment, heating may be performed in three or more separate times, or may be only one-time heating. ·In the above-described embodiment, the sintering start temperature of the copper component and the curing start temperature of the silicon component of the conductor paste are not limited to the example of the above-described embodiment.

[0074] ·In the plating step S15 of the above-described embodiment, the first metal layer 61C may be formed by other methods such as sputtering. ·In the above-described embodiment, the conductor paste may be nano-ink. In the case of nano-ink, it is prepared as follows. Nano metal powder is dispersed in a solvent containing cellosolves, carbitols, hydrocarbons, aromatics, and the like. Then, various silicone-modified resins, or silicone resins, or sol-gel materials, etc. are added in an amount of 0.001-10 wt% based on the weight of Cu alone. The conductor paste of nano-ink may be prepared in this way, or by a different method.

[0075] · In the above embodiment, the materials in the case of using the conductive paste as the complex ink are not limited to the examples of the above embodiment. For example, the amine compound may be any of primary amines, secondary amines, and tertiary amines, and further, the number of N atoms is not limited. For example, primary amines such as octylamine and hexylamine, secondary amines such as di-n-butylamine, and tertiary amines such as N,N-dimethylhexylamine may be used. Also, the amine compound may be an alcoholamine, a diamine, etc., and the positional relationship between the N atom and the OH group is not specified as α, β, γ positions, etc. Further, the number of N and O atoms in one molecule is not particularly limited. For example, α-hydroxyamines such as 2-dimethylaminoethanol and 2-ethylaminoethanol, β-hydroxyamines such as 3-amino-1-propanol and 4-amino-2-butanol may be used. Further, diamines such as ethylenediamine may be used, or cyclic diamines such as piperazine may be used. Also, the silicon component may be, for example, various silicone-modified resins such as epoxy resin, polyester resin, and phenol resin, and sol-gel materials, etc. Also, as the metal salt, a metal salt composed of formic acid, acetic acid, oxalic acid, and other organic acids may be adopted. Examples of this kind of metal salt include copper formate anhydride.

[0076] · In the above embodiment, the electronic component 10 may include a glass film. In that case, for example, the glass film may be formed so as to cover a part of the region of the outer surface 21 of the body 20. That is, even if there is a glass film covering the body 20, 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.

[0077] <Appendix> The technical ideas derivable from the above embodiment and the modified examples are described below. [1]An electronic component comprising a body and an external electrode covering a part of the outer surface of the body and not containing a silver component, the external electrode having a base electrode covering the outer surface of the body, the base electrode containing copper particles and a synthetic resin, and when the base electrode is bisected into a first portion located on the body side and a second portion located on the side opposite to the body, the average value of the particle size of the copper particles in the second portion is larger than the average value of the particle size of the copper particles in the first portion.

[0078] [2]The electronic component according to [1], wherein the ratio of the average value of the particle size of the copper particles in the second portion to the average value of the particle size of the copper particles in the first portion is 1.2 or more. [3]The electronic component according to [1] or [2], wherein the average value of the particle size of the copper particles in the second portion is 100 nm or more.

[0079] [4]The electronic component according to any one of [1] to [3], wherein the average value of the particle size of the copper particles in the first portion is 75 nm or less. [5]In a specific cross-section orthogonal to the outer surface of the base electrode, at least a part of the copper particles has an elliptical shape, and the acute angle formed by the major axis of the copper particles and the axis along the outer surface of the base electrode is 45 degrees or less. The electronic component according to any one of [1] to [4].

[0080] [6]The base electrode has voids in which the synthetic resin does not exist between the copper particles, and the ratio of the voids in the second portion is larger than the ratio of the voids in the first portion. The electronic component according to any one of [1] to [5].

[0081] [7]The external electrode further has a metal layer covering the outer surface of the base electrode and a mixed layer located between the metal layer and the base electrode. The mixed layer contains chemical components not contained in the base electrode and contained in the metal layer, and chemical components not contained in the metal layer and contained in the base electrode. The electronic component according to any one of [1] to [6].

Explanation of Reference Numerals

[0082] BD61A…Outer surface P1…First part P2…Second part PA…Gap 10…Electronic component 20…Element body 21…Outer surface 61…First external electrode 61A…First underlayer electrode 61B…First mixed layer 61C…First metal layer 63…Copper particles 64…Silicone resin

Claims

1. A base body, an external electrode that covers a part of the outer surface of the base body and does not contain a silver component, and is provided with, the external electrode has an underlying electrode that covers the outer surface of the base body, the underlying electrode contains copper particles and a synthetic resin, when the underlying electrode is bisected into a first portion located on the base body side and a second portion located on the side opposite to the base body, the average value of the particle diameter of the copper particles in the second portion is larger than the average value of the particle diameter of the copper particles in the first portion, the underlying electrode has voids in which the synthetic resin does not exist between the copper particles, the ratio of the voids in the second portion is larger than the ratio of the voids in the first portion electronic component.

2. A base body, an external electrode that covers a part of the outer surface of the base body and does not contain a silver component, and is provided with, the external electrode has an underlying electrode that covers the outer surface of the base body, the underlying electrode contains copper particles and a synthetic resin, when the underlying electrode is bisected into a first portion located on the base body side and a second portion located on the side opposite to the base body, the average value of the particle diameter of the copper particles in the second portion is larger than the average value of the particle diameter of the copper particles in the first portion, the external electrode further has a metal layer that covers the outer surface of the underlying electrode and a mixed layer located between the metal layer and the underlying electrode, the mixed layer contains chemical components that are not included in the underlying electrode and are included in the metal layer, and chemical components that are not included in the metal layer and are included in the underlying electrode electronic component.

3. The ratio of the average value of the particle diameter of the copper particles in the second portion to the average value of the particle diameter of the copper particles in the first portion is 1.2 or more The electronic component according to claim 1 or 2.

4. The average value of the particle diameter of the copper particles in the second portion is 100 nm or more The electronic component according to claim 1 or 2.

5. The average value of the particle diameter of the copper particles in the first portion is 75 nm or less The electronic component according to claim 1 or 2.

6. In a specific cross-section orthogonal to the outer surface of the underlying electrode, at least a part of the copper particles has an elliptical shape, the acute angle formed by the major axis of the copper particle and the axis along the outer surface of the underlying electrode is 45 degrees or less The electronic component according to claim 1 or 2.

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