Electronic Components

Abstract

The present invention provides an electronic component which is capable of suppressing the formation of a pinhole in a plating layer even if a corner part of a ceramic element is not completely covered with a base layer. The present invention provides an electronic component which is provided with a ceramic element and an external electrode that is provided on an end of the ceramic element, wherein: an end surface and two lateral surfaces, which are adjacent to each other, of the ceramic element are in contact with each other, thereby forming a corner part of the ceramic element; the external electrode is provided with a base layer which covers a plurality of lateral surfaces including the two lateral surfaces and the end surface excluding the corner part, and a plating layer which covers the base layer and the corner part; and the thickness of the plating layer covering the corner part is larger than the thickness of the plating layer covering the center of the end surface.

Description

[Technical field]

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

[0002] Chip-type ceramic electronic components having external electrodes on both ends of a ceramic body are known (e.g., Patent Documents 1 and 2). The external electrodes include a base layer (e.g., a conductive layer formed by applying and baking a conductive paste containing Cu, Ni, Ag, Pd, etc. as a main component) provided on the surface of the ceramic body, and a plating layer (e.g., a Ni plating layer) formed on the surface of the base layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-31988 A [Patent Document 2] JP 2012-69912 A Summary of the Invention [Problem to be solved by the invention]

[0004] In electronic components such as multilayer ceramic capacitors, it is desirable to make the base layer of the external electrodes thinner. By making the base layer thinner, it is possible to increase the size of the ceramic body and the number of internal electrodes without changing the external dimensions of the electronic component. This can improve the performance of the electronic component.

[0005] When a base layer is formed to cover the end portions (including the end faces and parts of the side faces) of the ceramic body, the thickness of the base layer covering the corner portions (where the end faces meet the two side faces) of the ceramic body tends to be thinner than the thickness of the base layer covering the end faces and side faces excluding the corners. Therefore, if the base layer is made thin, the base layer covering the corners of the ceramic body may become too thin, causing the corners to be exposed through the base layer.

[0006] Since the plating layer is formed on the surface of the conductive underlayer, the plating layer is generally not formed on the corners of the ceramic body exposed from the underlayer. However, by extending the plating time, the plating layer formed on the surface of the underlayer covering the periphery of the corners can be spread further to the surface of the corners. However, the plating layer covering the surface of the corners is thin and has a weak bond with the ceramic body. As a result, gaps are likely to form between the corners of the ceramic body and the plating layer. Furthermore, if the plating time is not sufficient, the plating layer cannot completely cover the corners of the ceramic body, and pinholes may form in the plating layer.

[0007] The presence of pinholes in the plating layer can cause the plating solution to penetrate into the inside of the plating layer, which can damage the ceramic body and internal electrodes, and thus poses the risk of reducing the reliability of electronic components.

[0008] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide an electronic component that can suppress the formation of pinholes in the plating layer even if the underlayer does not completely cover the corners of the ceramic body. [Means for solving the problem]

[0009] According to a first aspect of the present invention, there is provided an electronic component comprising a ceramic body and an external electrode provided on an end portion of the ceramic body, two adjacent side surfaces and an end surface of the ceramic body are in contact with each other to form corners of the ceramic body; the external electrode includes an undercoat layer that covers the end face and a plurality of side surfaces including the two side surfaces except for the corner portions, and a plating layer that covers the undercoat layer and the corner portions, An electronic component is provided in which the thickness of the plating layer covering the corners is greater than the thickness of the plating layer covering the center of the end face. Effect of the Invention

[0010] According to the electronic component of the present invention, even if the underlayer does not completely cover the corners of the ceramic body, the formation of pinholes in the plating layer can be suppressed. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1(a) is a schematic perspective view of an electronic component according to a first embodiment, and FIG. 1(b) is a schematic perspective view of a ceramic body used in the electronic component of FIG. 1(a). [Diagram 2] FIG. 2 is a schematic cross-sectional view of the electronic component taken along line XX in FIG. [Diagram 3] FIG. 3 is a schematic enlarged cross-sectional view of a portion of the electronic component shown in FIG. [Figure 4] FIG. 4 is a schematic enlarged cross-sectional view of a portion of the electronic component shown in FIG. [Diagram 5] FIG. 5(a) is a micrograph of the end face side of the electronic component according to the first embodiment, and FIG. 5(b) is an enlarged photograph of a part of FIG. 5(a). [Figure 6] 6(a) to 6(f) are schematic cross-sectional views illustrating the plating layer forming process. [Figure 7] FIG. 7(a) is a micrograph of a cross section of an electronic component produced in an example, and FIG. 7(b) is a micrograph of a cross section of an electronic component produced in a comparative example. [Figure 8] FIG. 8 is an enlarged photograph of a portion of the micrograph of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] An electronic component according to an embodiment of the present invention includes a ceramic body and an external electrode provided on a surface of the ceramic body. The external electrode includes an underlayer covering the surface of the ceramic body and a plating layer covering the underlayer. Two adjacent side surfaces and an end face of the ceramic body are in contact with each other to form corners of the ceramic body. The underlayer of the external electrode covers the end faces and a plurality of side surfaces of the ceramic body including the two side surfaces, except for the corners of the ceramic body. The corners of the ceramic body may be partially or entirely exposed from the underlayer.

[0013] When a plating layer is formed on the surface of such an underlayer, the plating layer is difficult to form on the surface of the corners of the ceramic body, which can cause pinholes to form in the plating layer. In addition, because the bonding strength between the corners of the ceramic body and the plating layer is weak, gaps are likely to form between them. If there are defects in the plating layer (pinholes, gaps, etc.), there is a risk that plating solution will penetrate into the inside of the plating layer. The penetrating plating solution can damage the ceramic body, which may reduce the reliability of electronic components.

[0014] In the electronic component according to an embodiment of the present invention, the occurrence of defects in the plating layer is suppressed by making the thickness of the plating layer covering the corners of the ceramic body thicker than the thickness of the plating layer covering the center of the end face.

[0015] As long as the electronic component comprises a ceramic body and external electrodes provided on the surface of the ceramic body, there are no particular limitations on the shape, dimensions, and material of the ceramic body, and the number, arrangement, and shape of the external electrodes. Internal electrodes may or may not be embedded within the ceramic body. If internal electrodes are present, they are electrically connected to the external electrodes in an appropriate manner.

[0016] Electronic components to which the configurations of the embodiments of the present invention can be applied include, for example, surface mount type, particularly chip components, and more specifically, capacitors such as multilayer ceramic capacitors, positive characteristic (or positive temperature coefficient, PTC) thermistors, negative characteristic (or negative temperature coefficient, NTC) thermistors, varistors, capacitors, etc. In the following embodiment 1, a multilayer ceramic capacitor having internal electrodes is taken as an example and will be described in detail with reference to the drawings.

[0017] [Embodiment 1] Fig. 1(a) is a schematic perspective view of an electronic component 10 according to a first embodiment of the present invention, and Fig. 1(b) is a schematic perspective view of a ceramic body 20 used in the electronic component 10 of Fig. 1(a). Fig. 2 is a schematic cross-sectional view of the electronic component 10 taken along line XX in Fig. 1(a). Fig. 3 is a schematic partially enlarged cross-sectional view of the electronic component 10 shown in Fig. 2, and Fig. 4 is a schematic partially enlarged cross-sectional view of the electronic component 10 shown in Fig. 3 at a further enlarged scale.

[0018] The electronic component 10 shown in Figures 1(a) and 2 is a multilayer ceramic capacitor. The electronic component 10 includes a ceramic body 20 and external electrodes 30, 40 provided on ends of the ceramic body 20. The external electrodes 30, 40 include base layers 31, 41 and plating layers 32, 42. The external electrodes 30, 40 may further include second plating layers 33, 43 that cover the plating layers 32, 42.

[0019] The ceramic body 20 of the multilayer ceramic capacitor is composed of multiple ceramic layers 200 (see FIG. 2). Internal electrodes 71, 72 are provided inside the ceramic body 20. The internal electrodes 71, 72 and the ceramic layers 200 are alternately stacked to form a laminate 80. The internal electrodes 71, 72 are exposed from either end face 21, 22 of the ceramic body 20 and are electrically connected to the external electrodes 30, 40.

[0020] Each component will be described in detail below.

[0021] (Ceramic body 20) As shown in Fig. 1(b), the ceramic body 20 according to embodiment 1 has a substantially rectangular parallelepiped shape and includes two opposing end faces 21, 22 and four side faces 23. Note that, in Fig. 1(b), internal electrodes 71, 72 exposed from the end faces 21, 22 are omitted for simplicity of the drawing. Two adjacent side surfaces 23 and an end face (end face 21 in FIG. 1( b )) of the ceramic body 20 are in contact with each other to form corners 25 (hatched regions) of the ceramic body 20 .

[0022] In this specification, the "corner 25 of the ceramic body 20" refers to a region including the vertex 25t where the two side surfaces 23 and the end face intersect and the portion surrounding the vertex 25t, and has a certain extent (see Figure 1(b)). Corner 25 may be, for example, an area surrounded by an arc of radius r drawn on side surface 23 and end surface 21 with vertex 25t as the center. The dimension (radius r) of corner 25 can be set appropriately in accordance with the dimension of electronic component 10. For example, in the case of a 0603 size electronic component 10, the dimension (radius r) of corner 25 can be 1 / 5 of the width W of electronic component 10 (i.e., W / 5). As described below, corner 25 (more precisely, ridge 25RL of corner 25) is covered with first plating region 321 of plating layer 32. Therefore, the area surrounded by an arc having a length 321R ( FIG. 5(b) ) of first plating region 321 and a radius r may be defined as corner 25 of ceramic body 20.

[0023] (base layer 31) As shown in FIGS. 2 to 4, the underlayer 31 of the external electrode 30 covers the side surfaces 23 and end surfaces 21 of the ceramic body 20 except for the corners 25 (FIG. 1(a)). Corner 25 of ceramic body 20 may be completely exposed from underlayer 31 (i.e., corner 25 may not be covered at all by underlayer 31). Alternatively, only a part of corner 25 may be exposed from underlayer 31, with the remaining part covered by underlayer 31. As one example, underlayer 31 covering corner 25 may be so thin that underlayer 31 cannot form a continuous film (i.e., multiple holes may be formed in underlayer 31, with part of corner 25 exposed through the holes). As another example, only a portion of corner 25 very close to vertex 25t (FIG. 1(b)) may be exposed from underlayer 31, with the remaining part of corner 25 being covered by underlayer 31.

[0024] The thickness of the base layer 31 does not have to be uniform. For example, the base layer 31 covering the corners 25 of the ceramic body 20 or their vicinity may be relatively thin, and the base layer 31 covering the other portions may be relatively thick.

[0025] The underlayer 31 is provided in order to form the plating layer 32 by electrolytic plating. Therefore, it is desirable that the thickness of the underlayer 31 is sufficient for electrolytic plating, but is as thin as possible. Specifically, the thickness 31t of the underlayer 31 is preferably 0.1 μm or more and 10 μm or less. By making the underlayer 31 thin, the thickness of the external electrode 30 (the total thickness of the underlayer 31, plating layer 32, and second plating layer 33) can be made thin. In this specification, the "thickness 31t of the base layer 31" refers to the maximum thickness of the base layer 31. The thickness 31t of the base layer 31 is usually approximately equal to the thickness of the plating layer covering the center 21c of the end faces 21, 22 of the ceramic body 20.

[0026] (Plating layer 32) The plating layer 32 of the external electrode 30 covers the base layer 31 and the portions of the corners 25 of the ceramic body 20 that are exposed from the base layer 31 . The plating layer 32 has three regions: a plating layer (first plating region) 321 covering the corner 25 of the ceramic body 20, a plating layer (second plating region) 322 provided on the end faces 21, 22 of the ceramic body 20, and a plating layer (third plating region) 323 provided on the side surface 23 of the ceramic body 20.

[0027] (Thickness T1 of first plating region 321) As shown in FIG. 3, a thickness T1 of the plating layer 32 (first plating region 321) covering the corner portion 25 is thicker than a thickness T2 of the plating layer 32 covering the center 21c of the end face 21 (FIG. 1(b)). By locally increasing the thickness of the plating layer 32 in the first plating region 321 that covers the corner portion 25, it is possible to prevent defects (such as pinholes in the plating layer 32 and gaps between the plating layer 32 and the ceramic body 20) from occurring in the first plating region 321. This makes it possible to prevent the plating solution from penetrating through the defects in the plating layer 32 and damaging the ceramic body 20 and the internal electrodes 71, 72 when the plating layer 32 is formed.

[0028] The thickness T1 of the first plating region 321 and the thickness T2 of the plating region 32 covering the center 21c of the end face 21 of the ceramic body 20 are measured as follows. First, electronic component 10 is cut at cross section CS (cross section along line XX in FIG. 1(a)) parallel to the LT plane. The position of cross section CS is determined so that it passes through corner portion 25 and exposes internal electrodes 71, 72 arranged inside ceramic body 20. Note that instead of cutting electronic component 10 at cross section CS, electronic component 10 may be polished up to cross section CS.

[0029] Fig. 3 shows a cross section of electronic component 10 taken along cross section SC. Ceramic body 20 shown in Fig. 3 has side surfaces 23, end surfaces 21, and ridge lines 25RL where these intersect. Here, ridge line 25RL will be described with reference to Fig. 1(b). Ceramic body 20 has ridge lines 20RL1 and 20RL2 where side surface 23 and end face 21 meet, and ridge line 20RL3 where two adjacent side surfaces 23 meet. Part of these ridge lines pass through corner 25. A ridge line within the range of corner 25 is referred to as "ridge line 25RL of corner 25."

[0030] Referring again to Figure 3, thickness T1 of first plating region 321 covering corner 25 is the distance from ridge 25RL of corner 25 of ceramic body 20 to the outer surface of first plating region 321 in a cross-sectional view of electronic component 10 (Figure 3). Note that ridge 25RL of corner 25 may have its edge removed during manufacturing, resulting in a curved surface (illustrated as a curved line in Figure 3).

[0031] Strictly speaking, thickness T2 of plating layer 32 covering center 21c of end face 21 of ceramic body 20 needs to be measured on a cross section of electronic component 10 cut along a plane passing through center 21c of end face 21. However, second plating region 322 shown in FIG. 3 and plating layer 32 covering center 21c of end face 21 have approximately the same thickness. Therefore, the thickness of second plating region 322 in the cross section of FIG. 3 is regarded as the thickness of plating layer 32 covering center 21c of end face 21. Hereinafter, the thickness of plating layer 32 covering center 21c of end face 21 may be referred to as thickness T2 of second plating region 322.

[0032] It is preferable that thickness T1 of first plating region 321 covering corner 25 is at least 1.5 times the thickness T2 (i.e., the thickness of second plating region 322) of plating layer 32 covering center 21c of end face 21. This makes thickness T1 of first plating layer 321 covering corner 25 sufficiently thick, further improving the effect of suppressing infiltration of plating solution into plating layer 32. More preferably, the thickness T1 of the first plating region 321 is at least twice the thickness T2 of the second plating region 322, and even more preferably, is at least three times and at most six times.

[0033] (Layer structure of first plating region 321) As shown in Fig. 4, first plating region 321 covering corner 25 is preferably made of a laminated film in which multiple plating films are laminated. In Fig. 4, first plating region 321 is made of three plating films 321a, 321b, and 321c. By using a laminated film, thickness T1 of first plating region 321 can be easily increased. The laminated film is preferably a laminate of 2 to 10 plating film layers, and more preferably a laminate of 2 to 4 plating film layers.

[0034] The number of layers of the plating film that constitutes the first plating region 321 (laminated film) is calculated as (the number of cracks CL) + 1. In Fig. 4, since there are two cracks CL, the plating film is counted as "3 layers." Cracks CL can be confirmed by observing the cross section of the first plating region 321 with a microscope (microscope or optical microscope) (FIGS. 7(a) and 8). When the first plating region 321 is observed with a microscope at a magnification of 100x or more, and gaps with a width of 1 μm or more are found to be continuous for 1 μm or more, it is determined to be a "crack CL."

[0035] (Length 321R of first plating region 321) Fig. 5(a) is a micrograph of an electronic component 10 according to Example 1, which will be described later, taken from the end face 21 side, and Fig. 5(b) is a micrograph of an enlarged portion of Fig. 5(a). As shown in Fig. 5(b), the dimension of first plating region 321 along ridge line 20RL1 of ceramic body 20 is designated "length 321R". Length 321R of first plating region 321 is, for example, not less than 0.1 µm and not more than 100 µm. Length 321R of first plating region 321 is more preferably not less than 20 µm and not more than 60 µm.

[0036] The length 321R of the first plating region 321 is measured as follows. 5(a) and (b) depict the side surface 23 of the ceramic body 20, the end surface 21 of the ceramic body 20, and the ridge lines 20RL1 and 20RL2 of the ceramic body 20. The side surface 23 and the end surface 21 are in contact with each other at the ridge line 20RL1 or ridge line 20RL2 of the ceramic body 20 (see also FIG. 1(b)). As shown in FIGS. 5(a) and (b), the plating layer 32 (first plating region 321) covering the corner portion 25 of the ceramic body 20 covers the apex 25t of the corner portion 25 of the ceramic body 20 and further extends along each of the ridge lines 20RL1 and 20RL2 of the ceramic body 20. In the end view of FIG. 5(a), the first plating region 321 has an L-shape.

[0037] The ceramic body 20 also has a ridge line 20RL3 where two adjacent side surfaces 23 meet (see FIG. 1(b)). The first plating region 321 further covers the apex 25t of the corner portion 25 of the ceramic body 20 and extends along the ridge line 20RL3 of the ceramic body 20. Note that length 321R of first plating region 321 along ridgeline 20RL1 of ceramic body 20 is substantially equal to the lengths of first plating region 321 measured along each of the other ridgelines 20RL2, 20RL3. Therefore, the length of first plating region 321 may be measured along either ridgeline.

[0038] 5(a) and (b), the first plating region 321 and the second plating region 322 have different thicknesses and surface properties, and therefore appear to have different color tones when observed under a microscope (microscope or optical microscope). Therefore, the extent of the first plating region 321 can be identified based on the color tone. After the extent of the first plating region 321 is identified, the length of the first plating region 321 is measured.

[0039] In the electronic component 10 according to the embodiment, it is possible to make the base layers 31, 41 thin without causing defects (pinholes, gaps, etc.) in the plating layers 32, 42. Therefore, for the following reasons, this is particularly suitable for electronic components 10 including internal electrodes 71, 72 inside the ceramic body 20, such as the multilayer ceramic capacitor shown in FIG. In the multilayer ceramic capacitor, the thickness of the external electrodes 30, 40 can be reduced by thinning the base layers 31, 41. This allows the number of internal electrodes 71, 72 to be increased without changing the external dimensions of the electronic component 10. This allows the capacitance of the multilayer ceramic capacitor to be improved. In other electronic components (such as multilayer thermistors) that have internal electrodes, the number of internal electrodes can be increased, thereby improving the electrical characteristics of the electronic components.

[0040] [Method of manufacturing electronic component 10] A method for manufacturing the electronic component 10 according to the first embodiment will be described using a multilayer ceramic capacitor having the structure shown in FIG. 2 as an example.

[0041] (Fabrication of Ceramic Body 20 and Internal Electrodes 71, 72) First, there is prepared the ceramic body 20 containing the internal electrodes 71, 72. The ceramic body 20 can be produced by any appropriate method.

[0042] The ceramic body 20 (more specifically, the ceramic layers 200) is made of a ceramic material suitable for the electronic component to be manufactured. For example, in a multilayer ceramic capacitor, the ceramic body 20 is made of a dielectric ceramic material (e.g., BaTiO3, CaTiO3, SrTiO3, CaZrO3, (BaSr)TiO3, Ba(ZrTi)O3, (BiZn)Nb2O7, etc.).

[0043] The internal electrodes 71, 72 are made of a conductive material, and suitable conductive materials include, for example, Ag, Cu, Pt, Ni, Al, Pd, and Au, with Ag, Cu, and Ni being particularly preferred.

[0044] In producing the ceramic body 20 and the internal electrodes 71, 72, first, each raw material of the ceramic body 20 is weighed and charged into a ball mill together with grinding media such as partially stabilized zirconia (PSZ) (hereinafter also referred to as PSZ balls) and pure water, and wet mixed and ground. The resulting mixture is calcined at a predetermined temperature (for example, 1000 to 1200°C) to obtain calcined powder. An organic binder is added to the calcined powder, and the mixture is wet mixed to form a slurry, which is then formed using a doctor blade method or the like to produce ceramic green sheets of a desired thickness.

[0045] Next, a conductive paste for forming the internal electrodes 71 and 72 is applied to the surface of the ceramic green sheet to form an internal electrode pattern. The conductive paste is prepared, for example, by dispersing a metal powder and an organic binder in an organic solvent. The conductive paste is applied, for example, by screen printing or the like.

[0046] After stacking a predetermined number of ceramic green sheets on which internal electrode patterns are formed, the sheets are sandwiched from above and below with ceramic green sheets on which internal electrode patterns are not formed, and pressed together. This results in a laminate (pre-sintered laminate) in which the ceramic green sheets and the internal electrode patterns are alternately stacked. This pre-sintered laminate is cut to a predetermined size, and then degreased and debindered, and fired at a predetermined temperature (1200 to 1400°C) in a predetermined atmosphere. In this way, a laminate 80 is obtained, which has a laminate structure in which a plurality of ceramic layers 200 and internal electrodes 71, 72 are alternately stacked. This laminate 80 can also be regarded as a ceramic body 20 containing the internal electrodes 71, 72.

[0047] (Formation of Underlayers 31 and 41) 2, base layers 31, 41 are formed so as to cover the ends of the ceramic body 20 (end faces 21, 22 and parts of the side faces 23 of the ceramic body 20 as shown in FIG. 2). The base layers 31, 41 are in contact with internal electrodes 71, 72 exposed at the end faces 21, 22 of the ceramic body 20. The underlayers 31 and 41 are formed of a metal material containing, for example, Cu, Ag, Si, Ni, etc. In particular, it is preferable to form them from a Cu film.

[0048] The underlayers 31 and 41 can be formed by a known film forming method. For example, a sputtering method, a vapor deposition method, a coating method (a conductive paste is applied to a predetermined position and then baked), a dipping method, etc. can be used. For example, a Cu film is preferably formed by a method in which a Cu paste is applied and then baked. By forming the Cu film thinly, the corners 25 of the ceramic body 20 are at least partially exposed from the underlayers 31 and 41 .

[0049] (Formation of plating layers 32, 42) The plating layers 32 , 42 are formed to cover the underlayers 31 , 41 and the portions of the corners 25 of the ceramic body 20 that are exposed from the underlayer 31 . The plating layers 32, 42 can be formed by electrolytic plating of at least one of Ni and Cu, for example. The plating layers 32, 42 are formed using a plating method capable of applying an impact to an object to be plated, such as a barrel plating method in which conductive media and the ceramic body 20 placed in a barrel are plated while being rotated and stirred, or a centrifugal plating method in which the ceramic body 20 is plated by being stirred by the centrifugal force of a barrel. This allows the plating layer 32 (first plating region 321) covering the corner portion 25 of the ceramic body 20 to be formed into a thick film.

[0050] The mechanism for thickening the first plating region 321 will be described in detail below with reference to the drawings, taking the centrifugal plating method as an example.

[0051] As shown in FIG. 6(a), the base layers 31, 41 are formed so that the corners 25 of the ceramic body 20 are exposed, and then the plating layer 32a is formed on the surfaces of the base layers 31, 41 by centrifugal plating. The plating layer 32a is first formed on the surfaces of the underlayers 31, 41 and spreads over time to the surfaces of the corners 25 of the ceramic body 20 (FIG. 6(b)).

[0052] The plating layer 32a covering the corners 25 of the ceramic body 20 has a weak bond to the surfaces of the corners 25. During centrifugal plating, the plating layer 32a easily peels off from the surfaces of the corners 25 due to collisions between the ceramic bodies 20, between the ceramic bodies 20 and the conductive media, and between the ceramic bodies 20 and the cathode, as well as friction when the ceramic bodies 20 stick to the cathode due to centrifugal force (FIG. 6(c)). As a result, the corners 25 are exposed from the plating layer 32a. Note that the bonding strength between the plating layer 32a and the underlayers 31 and 41 is strong, so the plating layer 32a only peels off partially.

[0053] With part of the plating layer 32a peeled off, plating continues. Using the underlayer 31, 41 and / or the previously formed plating layer 32a as a base point, a plating layer 32b is formed again to cover the surface of the corner 25 (FIG. 6(d)). The previously formed plating layer 32a also increases in thickness. In particular, the plating layer 32a peeled off from the corner 25 grows on both the inner side (the side that was in contact with the surface of the corner 25 before peeling) and the outer side.

[0054] As in FIG. 6(c), the plating layer 32b covering the corner 25 easily peels off from the surface of the corner 25 due to the various collisions and friction (as described above) that the ceramic body 20 may be subjected to during centrifugal plating (FIG. 6(e)). If plating is continued after plating layer 32b has peeled off, plating layer 32c is formed again, covering the surface of corner 25, using underlayer 31, 41 and / or previously formed plating layers 32a, 32b as base points (FIG. 6(f)). Also, previously formed plating layers 32a, 32b increase in thickness. In particular, plating grows on both the inside and outside of the peeled portions of plating layers 32a, 32b.

[0055] In this way, by repeatedly forming and peeling off the plating layer covering the corner 25, the plating layer 32 (first plating region 321) covering the corner 25 can be made thicker than the other parts of the plating layer 32 (second plating region 322, third plating region 323). The thickness T1 of the first plating region 321 can be adjusted by the length of the plating time. By increasing the plating time, the thickness T1 of the first plating region 321 can be increased.

[0056] The number of layers of plating films 321a, 321b, 321c that form first plating region 321 is determined by the number of times of peeling. The number of layers of plating films 321a, 321b, 321c can be controlled by adjusting the strength of the impact that ceramic body 20 (more precisely, the plating film formed on the surface of ceramic body 20) receives during centrifugal plating (which can be adjusted by, for example, the rotation speed of the container (barrel) that contains the chips and media) and by adjusting the plating time, thereby controlling the number of times of peeling. The plating time is preferably in the range of 30 to 600 minutes, and the rotation speed is preferably in the range of 200 to 500 rpm.

[0057] (Formation of second plating layers 33, 43) The second plating layers 33, 43 are formed so as to cover the surfaces of the plating layers 32, 42. The second plating layers 33, 43 can be formed, for example, by electrolytic plating of Sn. The second plating layers 33, 43 can be formed by a known plating method, for example, barrel plating, centrifugal plating, or the like. EXAMPLES

[0058] The measurement samples were prepared according to the following procedure.

[0059] Example 1 The ceramic body 20 was prepared by grinding and mixing the raw materials, calcining, molding, firing, and cutting. The raw materials were ground and mixed by mixing a predetermined amount of BaTiO3 as a main component, followed by grinding, and calcining at a maximum temperature of 1200°C in an air atmosphere. An organic binder was added to the obtained calcined powder and wet-mixed to obtain a slurry. A ceramic green sheet of a desired thickness was produced from the slurry by a doctor blade method. Next, an internal electrode conductive paste (Ag paste) was applied to the surface of the ceramic green sheet to form an internal electrode pattern. A predetermined number of ceramic green sheets on which the internal electrode pattern was formed in this way were stacked, and then the top and bottom were sandwiched and pressed with ceramic green sheets on which the internal electrode pattern was not formed, to produce a laminate. This laminate was cut to a predetermined size, and then degreased and debindered, and then fired at a predetermined temperature (1200 to 1400°C) and in a predetermined atmosphere to obtain a laminate 80 having a laminate structure consisting of the ceramic body 20 and the internal electrodes 71 and 72.

[0060] A Cu paste was applied to the edge of the ceramic body 20 and baked to form an underlayer 31. At this time, the corners 25 of the ceramic body 20 were exposed from the underlayer 31 (FIGS. 7(a) and 8). Next, a plating layer 32 (Ni plating layer) was formed by centrifugal plating to cover the surface of the underlayer 31 and the corners 25 of the ceramic body 20. When centrifugal plating was performed, the rotation speed of the barrel (a container for holding chips and media) was increased and the plating time was increased compared to general centrifugal plating conditions. This allowed the Ni plating layer to be laminated at the corners 25 of the ceramic body 20, which are susceptible to impact.

[0061] Further, a second plating layer 33 (Sn plating layer) covering the Ni plating layer was formed by centrifugal plating under general plating conditions. In this manner, a multilayer ceramic capacitor was obtained (sample of Example 1).

[0062] The sample was embedded in resin and polished up to line XX in FIG. 1(a) to expose the cross section SC (parallel to the LT plane), and then ion milling was performed. The first plating regions 321 of the external electrodes 30, 40 were observed with a microscope (Keyence: VHX7000). Micrographs of the sample of Example 1 are shown in FIGS. 7(a) and 8. In the sample of Example 1, the first plating region 321 covering the corner portion 25 of the ceramic body 20 was a laminated film of three layers of Ni plating films 321a, 321b, and 321c (FIG. 8). Furthermore, no pinholes were present in the Ni plating layer 32. Length 321R (FIG. 5(b)) of first plating region 321 was measured and found to be approximately 55 μm.

[0063] Comparative Example 1 A sample of Comparative Example 1 was produced using the same process as Example 1, except for the conditions for forming the plating layer 32 (Ni plating layer). In the sample of Comparative Example 1, the Ni plating layer 32 was plated under typical centrifugal plating conditions. This reduced the impact on the corners 25 of the ceramic body 20 and suppressed lamination of the Ni plating layer 32.

[0064] After the second plating layer (Sn plating) was peeled off from the sample of Comparative Example 1, it was processed in the same manner as the sample of Example 1, and the corners of the external electrodes 30 were observed with a microscope (Keyence: VHX7000). A micrograph of the sample of Comparative Example 1 is shown in Fig. 7(b). In the sample of Comparative Example 1, the Ni plating layer 32 was thinner in the portion covering the corner 25 of the ceramic body 20 than in the other portion, resulting in pinholes PH.

[0065] Moreover, 10,000 pieces each of the sample of Example 1 and the sample of Comparative Example 1 were produced and evaluated as follows. Number of plating solution intrusions: The number of samples in which plating solution infiltrated inside the Ni plating layer was counted. The cross sections of the external electrodes 30 and the ceramic body 20 in their vicinity were observed under a microscope, and if plating deposits or cavities of 1 μm or more were observed inside the external electrodes 30 and / or inside the ceramic body 20, it was determined that plating solution had infiltrated. Reliability evaluation: An IR (Insulation Resistance) measurement was performed under environmental load, and the number of defective products was counted. In the IR measurement, the insulation resistance value was measured after a certain period of time (24 hours or more) had passed in a high temperature (70°C or higher) and high humidity (50% or higher) environment, and it was confirmed whether the initial insulation resistance value was maintained. If the measured insulation resistance value exceeded 90% of the initial insulation resistance value, it was deemed OK (good product), and if it was below 90%, it was deemed NG (defective product).

[0066] [Table 1]

[0067] As shown in Table 1, in Comparative Example 1, the infiltration of plating solution was confirmed in 521 out of 10,000 samples, whereas in Example 1, the infiltration of plating solution was not confirmed in any of the 10,000 samples. Regarding the reliability evaluation, 26 out of 10,000 samples were defective in Comparative Example 1. In Example 1, there were no defective out of 10,000 samples.

[0068] This application claims priority based on Japanese Patent Application No. 2022-037424, filed in Japan on March 10, 2022, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0069] 10. Electronic Components 20 Ceramic body 200 ceramic layers 21, 22 End faces of ceramic body 21c Center of end face 23 Side of ceramic body 25 Corner of ceramic body 30, 40 external electrode 31, 41 Base layer 31t Thickness of the base layer 32, 42 Plating layer 321 Plating layer covering the corners (first plating area) 321R Length of plating layer covering corner 321a, 321b, 321c Plating film 322 Second plating area 323 3rd Plating Area 33, 43 Second plating layer 71, 72 Internal electrode 80 Laminate T1 Thickness of the first plating area T2 Thickness of the second plating area 20RL1, 20RL2, 20RL3 Ridge line of ceramic body 25RL Corner ridge

Claims

1. An electronic component comprising a ceramic body and an external electrode provided at an end of the ceramic body, two adjacent side surfaces and an end surface of the ceramic body are in contact with each other to form corners of the ceramic body; the external electrode includes an undercoat layer that covers the end face and a plurality of side surfaces including the two side surfaces except for the corner portions, and a plating layer that covers the undercoat layer and the corner portions, the thickness of the plating layer covering the corner portion is greater than the thickness of the plating layer covering the center of the end face, The electronic component has only the plating layer covering the corner portion, which is made of a laminate film in which a plurality of plating films are laminated.

2. The electronic component according to claim 1 , wherein the thickness of the plating layer covering the corner portions is at least 1.5 times the thickness of the plating layer covering the center of the end face.

3. The electronic component according to claim 1 , wherein the laminated film is formed by laminating 2 to 10 plating film layers.

4. An electronic component comprising a ceramic body and an external electrode provided at an end of the ceramic body, two adjacent side surfaces and an end surface of the ceramic body are in contact with each other to form corners of the ceramic body; the external electrode includes an undercoat layer that covers the end face and a plurality of side surfaces including the two side surfaces except for the corner portions, and a plating layer that covers the undercoat layer and the corner portions, the thickness of the plating layer covering the corner portion is greater than the thickness of the plating layer covering the center of the end face, the plating layer covering the corner portion has a length along a ridge where the side surface and the end surface meet, the length being 20 μm or more and 60 μm or less.

5. The electronic component according to claim 1 , further comprising an internal electrode inside the ceramic body.

Images