Multilayer ceramic capacitor

Abstract

Provided is a multilayer ceramic capacitor that, while being provided with a laminate of a prescribed size, has formed thereon a flat external electrode having no bulges in a central part.　In a multilayer ceramic capacitor 1, the dimensions of a laminate 10 are 0.8 mm or greater in a lamination direction T, 0.8 mm or greater in a width direction W, and 1.6 mm or greater in a length direction L. An external electrode 16 contains Cu, the thickness of the external electrode 16 on a principal surface 11 being 15 μm or less, and the angle formed between the principal surface 11 and the surface of a peripheral edge part E of the external electrode 16 being 39.1 degrees or less. The ratio b / a of the maximum thickness b of the external electrode 16 when viewing a cross-section defined in the lamination direction T and the width direction W at the center in the width direction W of the multilayer ceramic capacitor 1, and the length-direction distance a from a terminal of any internal electrode layers positioned at the two ends in the lamination direction T to the surface of the external electrode when viewing a cross-section defined in the lamination direction T and the length direction L at a position where a side-surface portion of an internal electrode exposed to an end surface 13 is exposed, is 2.8 or lower.

Description

Multilayer ceramic capacitors

[0001] The present invention relates to a multilayer ceramic capacitor.

[0002] Conventionally, multilayer ceramic capacitors are manufactured by forming external electrodes on the outer surfaces of a laminate in which a plurality of dielectric layers and a plurality of internal electrodes are stacked.

[0003] A known method for forming external electrodes involves immersing the end surfaces of a laminate (hereinafter referred to as a "sintered laminated chip") before the external electrodes are formed in an external electrode paste containing a resin as a binder, a metal, and a solvent, and then drying the applied external electrode paste. Generally, as the sintered laminated chip becomes larger, a larger amount of external electrode paste is applied, which tends to result in an external electrode that is thick in the center and thin at the periphery, forming a convex shape. Meanwhile, a known technique is to form external electrodes with improved flatness by generating convection due to evaporation of the solvent in the external electrode paste after it is applied to the sintered laminated chip and before it dries.

[0004] JP 2013-71986 A JP 2021-77750 A

[0005] When a large-sized fired chip laminate is coated with the external electrode paste that generates the above-mentioned convection, a large amount of the external electrode paste adheres not only to the edges of the fired chip laminate but also to the main surfaces and side surfaces that wrap around from the edges, and convection occurs more prominently on the main surfaces and side surfaces, resulting in flattening of the end faces, main surfaces, and side surfaces of the external electrodes after drying. However, because the main surfaces and side surfaces are flattened with a large amount of external electrode paste applied, the angle between the main surfaces or side surfaces of the laminate and the peripheral surface of the external electrodes becomes large, and the peripheral surfaces of the external electrodes become more likely to peel off from the laminate.

[0006] The present invention is devised to solve the above-mentioned problems, and aims to provide a multilayer ceramic capacitor having external electrodes that can prevent the central portion from expanding compared to the peripheral portion while having a laminate of a predetermined size, and can prevent the peripheral portion from peeling off from the laminate.

[0007] The inventors discovered that by adjusting the material constituting the external electrode and the dimensions of specific locations on the external electrode, it is possible to form an external electrode that prevents the central portion from expanding compared to the peripheral portion, while preventing the peripheral portion from peeling off from the laminate, and thus completed the present invention.

[0008] That is, the present invention provides a multilayer ceramic capacitor comprising: a laminate in which dielectric layers and internal electrodes are laminated, the laminate having two main surfaces opposing each other in a lamination direction, two side surfaces opposing each other in a width direction intersecting the lamination direction, and two end surfaces opposing each other in a length direction intersecting the lamination direction and the width direction; and external electrodes formed on outer surfaces of the laminate, wherein the dimensions of the laminate are 0.8 mm or more in the lamination direction, 0.8 mm or more in the width direction, and 1.6 mm or more in the length direction, the external electrodes contain Cu, the thickness of the external electrodes in the lamination direction on the main surfaces of the laminate is 15 μm or less, the angle formed between the main surfaces and peripheral surfaces of the external electrodes on the main surfaces of the laminate is 39.1 degrees or less, and the maximum thickness b of the external electrodes in the length direction when viewing a cross section of the multilayer ceramic capacitor at the center in the width direction of the multilayer ceramic capacitor, the cross section being defined by the lamination direction and the length direction, When a cross section of the multilayer ceramic capacitor defined in the stacking direction and the length direction is viewed at a position where a side portion of the internal electrode exposed on the end face of the laminate is exposed, the ratio b / a of the lengthwise distance a from either end of the internal electrode layer located at both ends in the stacking direction to the surface of the external electrode is 2.8 or less.

[0009] According to the present invention, it is possible to provide a multilayer ceramic capacitor having a laminate of a predetermined size, which is capable of suppressing swelling of the central portion compared to the peripheral portion, and which is equipped with external electrodes that can suppress peeling of the peripheral portion from the laminate.

[0010] 1 is a perspective view of the appearance of a multilayer ceramic capacitor 1 according to one embodiment of the present invention; FIG. 2 is a cross-sectional view taken along line II-II of the multilayer ceramic capacitor 1 shown in FIG. 1; and FIG. 3 is a cross-sectional view taken along line III-III of the multilayer ceramic capacitor 1 shown in FIG. 1. (a) is a diagram schematically showing a cross-section of the multilayer ceramic capacitor of the present invention, and (b) is a diagram schematically showing a cross-section of a conventional multilayer ceramic capacitor. This diagram shows the external shape and cutting position of a laminate used when examining the flatness of the external electrodes. This diagram explains the angle between the main surface of the laminate and the peripheral surface of the external electrodes. This diagram is for explaining the process of applying external electrode paste to a laminated chip sintered body, where (a) shows the laminated chip sintered body immersed in the external electrode paste, (b) shows the laminated chip sintered body being pulled up, generating an outward flow of the external electrode paste from the center to the peripheral edge, and (c) shows the external electrode paste having dried.

[0011] Hereinafter, embodiments of the multilayer ceramic capacitor of the present invention will be described, but the present invention is not limited thereto. Furthermore, the drawings may be drawn in a simplified and schematic manner to explain the contents of the invention, and the dimensional ratios of the depicted components or between the components may not match the dimensional ratios of those components described in the specification. Furthermore, components described in the specification may be omitted in the drawings, or the number of components may be omitted.

[0012] Fig. 1 is an external perspective view of a multilayer ceramic capacitor 1 according to one embodiment of the present invention. Fig. 2 is a cross-sectional view of the multilayer ceramic capacitor 1 taken along line II-II of Fig. 1, showing a cross section defined by the stacking direction T and the length direction L at the center of the width direction W of the multilayer ceramic capacitor 1. Fig. 3 is a cross-sectional view of the multilayer ceramic capacitor 1 taken along line III-III of Fig. 1, showing a cross section defined by the stacking direction T and the width direction W at the center of the length direction L of the multilayer ceramic capacitor 1.

[0013] 1 to 3, a multilayer ceramic capacitor 1 has a laminate 10 having a rectangular parallelepiped shape and a pair of external electrodes 16. The pair of external electrodes 16 are arranged to face each other as shown in FIG.

[0014] Here, the direction in which a pair of external electrodes 16 face each other is defined as the length direction L of the multilayer ceramic capacitor 1, the direction in which dielectric layers 14 and internal electrodes 15 (described later) are stacked is defined as the stacking direction T, and the direction perpendicular to both the length direction L and the stacking direction T is defined as the width direction W. The length direction L, stacking direction T, and width direction W are perpendicular to one another.

[0015] (Laminate) The laminate 10 has a first end face 13 a and a second end face 13 b facing each other in the longitudinal direction L, a first main surface 11 a and a second main surface 11 b facing each other in the stacking direction T, and a first side surface 12 a and a second side surface 12 b facing each other in the width direction W.

[0016] The corners and ridges of the laminate 10 are preferably rounded. Here, a corner is a portion where three surfaces of the laminate 10 intersect, and a ridge is a portion where two surfaces of the laminate 10 intersect.

[0017] 2 and 3, the laminate 10 includes a plurality of laminated dielectric layers 14 and a plurality of laminated internal electrodes 15. The internal electrodes 15 include first internal electrodes 15a and second internal electrodes 15b. The laminate 10 has a structure in which the first internal electrodes 15a and the second internal electrodes 15b are alternately laminated in the lamination direction T with the dielectric layers 14 interposed therebetween.

[0018] As shown in Figure 3, the dielectric layer 14 forms an outer layer 141 located outside the stacking direction T of the internal electrode 15 located outermost in the stacking direction T, an inner layer dielectric layer 142 located between two internal electrodes 15 adjacent to each other in the stacking direction T, and a margin portion 143 which is an area where no internal electrode 15 is present when the ceramic body 10 is viewed in the stacking direction T.

[0019] That is, the outer layer 141 is a layer located between the internal electrode 15 located outermost in the stacking direction T and the first main surface 11a and second main surface 11b of the ceramic body 10. The internal dielectric layer 142 is a layer located between the first internal electrode 15a and the second internal electrode 15b adjacent to each other in the stacking direction T. The margin portion 143 is a portion located outside the outer layer 141 and the internal dielectric layer 142 in the width direction W.

[0020] In the manufacturing process of the multilayer ceramic capacitor 1, the margin portion 143 may be formed integrally with the inner dielectric layer 142, or may be formed separately from the inner dielectric layer 142. When the margin portion 143 is formed separately from the inner dielectric layer 142, for example, the margin portion 143 can be formed by laminating ceramic green sheets on which internal electrode patterns are formed, and then attaching a ceramic green sheet to the outside in the width direction W and firing the laminate. In this case, a physical boundary exists between the margin portion 143 and the laminate including the outer layer 141, the internal electrode 15, and the inner dielectric layer 142.

[0021] To manufacture the laminate, first prepare an unfired laminated chip that will have the structure described above after firing. The laminated chip is then fired to obtain a fired laminated chip. The external electrode paste described below is applied to the outer surface of the fired laminated chip, and then the fired laminated chip is fired together with the external electrode paste to complete a laminate with external electrodes, i.e., a multilayer ceramic capacitor.

[0022] In the following explanation of the manufacturing method, etc., the process of applying external electrode paste to the laminated chip sintered body before the external electrodes are formed will be described in detail. However, in this specification, since the laminated chip sintered body and the laminate have substantially the same shape and structure, the laminated chip sintered body and each of its parts will be described using the same symbols as the laminate.

[0023] (Size of Laminate) The laminate is formed by applying paste to the end faces of the fired laminated chip body and to parts of the subsequent main surfaces and side surfaces, and then firing the paste. This paste promotes convection during drying after application, reducing the thickness of the central portion C of the external electrode 16. However, as the fired laminated chip body 10 becomes larger, a larger amount of external electrode paste is applied, and the formed external electrode 16 tends to have a convex shape with a thick central portion C and a thin peripheral portion S. As a result of promoting convection during drying, the thickness of the external electrode 16 on the main surface 11 and side surface 12 of the fired laminated chip body 10 increases, and the angle between the main surface 11 or side surface 12 and the surface of the peripheral portion E increases, making the peripheral portion E of the external electrode 16 more likely to peel off from the laminate. The present invention can form an external electrode that prevents the central portion C from expanding compared to the peripheral portion S, does not become convex, and suppresses peeling of the peripheral portion E from the laminate 10, even if the laminate 10 after firing has a size of 0.8 mm or more in the stacking direction, 0.8 mm or more in the width direction, and 1.6 mm or more in the length direction.

[0024] (External Electrodes) The external electrodes 16 include a first external electrode 16a and a second external electrode 16b.

[0025] The first external electrode 16a is disposed on the first end face 13a of the laminate 10 and is connected to the first internal electrode 15a. The first external electrode 16a extends from the first end face 13a to a portion of the first principal surface 11a and a portion of the second principal surface 11b. The first external electrode 16a also extends from the first end face 13a to a portion of the first side surface 12a and a portion of the second side surface 12b.

[0026] The second external electrode 16b is disposed on the second end face 13b of the laminate 10 and is connected to the second internal electrode 15b. The second external electrode 16b extends from the second end face 13b to a portion of the first principal surface 11a and a portion of the second principal surface 11b. The second external electrode 16b also extends from the second end face 13b to a portion of the first side surface 12a and a portion of the second side surface 12b.

[0027] Here, the central portion C of the external electrode 16 refers to a region located near the center of the end face 13 of the external electrode 16, which is formed so as to be continuous with the end face 13 of the laminate 10 and cover part of the main face 11 and side face 12, and the peripheral portion S of the external electrode 16 refers to a region surrounding the central portion C of the external electrode 16 on the end face 13 of the laminate 10. In addition, the peripheral portion E of the external electrode 16 refers to a region located from the end of the external electrode 16, which is formed around the entire periphery of the main face 11 and side face 12 of the laminate 10, toward the end face 13 of the laminate 10.

[0028] The external electrodes contain Cu, which is blended as a component of the external electrode paste described below, and which is applied to the end faces 13 of the fired laminated chip body 10 to form the external electrodes.

[0029] (Shape of External Electrodes) Figure 4(a) is a diagram schematically showing a cross section of the multilayer ceramic capacitor 1 of the present invention. On the other hand, Figure 4(b) is a diagram schematically showing a cross section of a conventional multilayer ceramic capacitor 1. These correspond to cross sections taken along line II-II of the multilayer ceramic capacitor 1 shown in Figure 1, but in order to explain the shape of the external electrodes, the cross-sectional shapes of the external electrodes are enlarged and shown schematically.

[0030] As shown in Figure 4(b), the external electrodes 16 of the conventional multilayer ceramic capacitor 1 have a convex shape that is thick in the center C and thin in the peripheral portion S. In contrast, the external electrodes 16 of the multilayer ceramic capacitor 1 of the present invention have a flat shape as shown in Figure 4(a), and are prevented from having the convex shape seen in the past. As a result, when compared at the same size, the external electrodes can be made thinner and the internal elements can be made larger, thereby enabling an increase in capacitance.

[0031] (Evaluation of Flatness) The flatness of the external electrodes can be evaluated based on the ratio of the film thicknesses of the external electrodes when the multilayer ceramic capacitor is cut along line A-A and line B-B shown in Figure 5. That is, the maximum thickness b of the external electrodes in the longitudinal direction L is measured when viewing a cross section of the multilayer ceramic capacitor taken along line B-B, which is defined by the stacking direction T and the length direction L, at the center of the width direction W of the multilayer ceramic capacitor. Also, when viewing a cross section of the multilayer ceramic capacitor taken along line A-A, which is defined by the stacking direction T and the length direction L, at a position where the side portions of the internal electrodes 15 exposed at the end faces 13 of the laminate 10 are exposed, the distance a in the longitudinal direction L from either end of the internal electrode layers 15 located at both ends in the stacking direction T to the surface of the external electrode is measured. Note that in Figure 5, in order to illustrate line A-A and line B-B in the laminate 10, the end faces 13 and the external electrodes formed on the subsequent main surfaces 11 and parts of the side faces 12 are omitted.

[0032] The flatness of the external electrodes can be evaluated by the ratio b / a of the maximum thickness b measured by the above method to the distance a. The closer b / a, which indicates the flatness of the external electrodes, is to 1, the better, and b / a in the multilayer ceramic capacitor 1 of the present invention is 2.8 or less.

[0033] Fig. 6 is an enlarged view of the peripheral portion E of the external electrode 16 on the main surface 11 of the laminate 10 in the cross section taken along line B-B in Fig. 5. On the main surface 11 of the laminate 10, the angle formed between the main surface 11 and the surface of the peripheral portion E of the external electrode 16 is determined by the angle θ formed between the main surface 11 of the laminate 10 and a straight line connecting the end of the external electrode 16 and the surface of the external electrode 16 located 10 µm from the end in the longitudinal direction L.

[0034] In the multilayer ceramic capacitor 1 of the present invention, the angle formed between the main surface 11 of the laminate 10 and the surface of the peripheral edge E of the external electrode 16 is 39.1 degrees or less. The thickness of the external electrode 16 on the main surface 11 of the laminate 10 in the stacking direction T is 15 μm or less.

[0035] (Formation of external electrodes) The multilayer ceramic capacitor 1 can be manufactured by applying an external electrode paste to the end faces 13 of the multilayer chip sintered body 10 and to the subsequent main faces 11 and parts of the side faces 12, and then drying and firing the multilayer chip sintered body 10 together to form the external electrodes 16.

[0036] (External Electrode Paste) The external electrode paste in this embodiment contains a binder, Cu, a glass filler, and a solvent.

[0037] (Binder) Any known binder can be used, but it is preferable that the binder contains a resin in which an Ethocel resin and an acrylic resin are copolymerized. By containing such a resin, the interfacial tension generated between the resin and the solvent increases the force of the outward flow of the external electrode paste from the central portion C to the peripheral portion S, thereby improving fluidity and preventing the central portion C from swelling compared to the peripheral portion S when applied.

[0038] The Ethocel resin is, for example, at least one of ethyl cellulose, methyl cellulose, hydroxypropyl cellulose, trityl cellulose, acetyl cellulose, carboxymethyl cellulose, and nitrocellulose.

[0039] The acrylic resin is, for example, at least one of isobutyl methacrylate, methyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, n-butyl methacrylate, and 2-ethylhexyl methacrylate.

[0040] The ETHOCEL resin and the acrylic resin are at least partially copolymerized. For example, the OH group of the ETHOCEL resin is substituted with a vinyl group, and the ETHOCEL resin and the acrylic resin are bonded together via the substituted vinyl group.

[0041] A dried coating film obtained by applying a paste for external electrodes containing a resin in which an ETHOCEL resin and an acrylic resin are at least partially copolymerized has flexibility derived from the acrylic resin and rigidity derived from the ETHOCEL resin, and has sufficient strength as a dried coating film.

[0042] On the other hand, when an external electrode paste containing only an Ethocel resin and an acrylic resin without copolymerization is used, the dried coating film becomes brittle, and therefore, multilayer ceramic capacitors coated with such an external electrode paste may suffer from chipping or peeling of the dried coating film during transportation.

[0043] (Cu) Cu particles are particles made of at least one of Cu and a Cu alloy. The average particle size D50 of Cu is preferably 0.3 μm or less in order to form thin and dense external electrodes.

[0044] (Glass Filler) As the glass filler, for example, oxides of Ba, Sr, Ca, Zn, Al, Si, B, etc. can be used. Furthermore, in order to form thin and dense external electrodes, it is preferable that the glass filler has an average particle size D50 of 1.0 μm or less.

[0045] (Solvent) The solvent may include, for example, at least one of terpineol, dihydroterpineol, dihydroterpinyl acetate, propylene glycol phenyl ether, benzyl alcohol, texanol, and butyl carbitol acetate.

[0046] FIG. 7 is a diagram illustrating the process of applying the external electrode paste 160 to the fired laminated chip body 10. As shown in FIG.

[0047] The end surface 13 of the sintered laminated chip body 10 is immersed in the external electrode paste 160 (FIG. 7(a)), and then pulled up (FIG. 7(b)). When the sintered laminated chip body 10 is pulled up, Marangoni convection occurs inside the external electrode paste 161 attached to the sintered laminated chip body 10, as shown by the arrows in FIG. 7(b).

[0048] The peripheral or edge portion dries more easily than the center portion, resulting in a decrease in the solvent concentration. To compensate for this decrease in solvent concentration, solvent is supplied from the center portion, resulting in an outward flow from the center portion to the peripheral portion and then to the edge portion (Figure 7(b)).

[0049] Because ETHOCEL resins have rigidity and heat storage properties, they prevent the external electrode paste from solidifying during flow during the drying process and promote outward flow, thereby promoting the flow of the external electrode paste from the center to the periphery and preventing the external electrode paste from bulging outward in the center ( FIG. 7( c) ).

[0050] In this way, by preventing the central portion from bulging out compared to the peripheral portion, it is possible to manufacture a multilayer ceramic capacitor having external electrodes with a flat shape.

[0051] As a method for applying the external electrode paste to the end face 13 and part of the main surface of the laminated chip sintered body 10, a method of immersing the end face 13 and part of the main surface of the laminated chip sintered body 10 in the external electrode paste 160 has been shown, but the method for applying the external electrode paste is not limited to this.

[0052] Evaluation tests carried out on the multilayer ceramic capacitor of the present invention and the conventional multilayer ceramic capacitor are shown below as Example 1 and Comparative Example 1, respectively.

[0053] Example 1

[0054] (External electrode paste A) The following raw materials were mixed in a roll mill to prepare external electrode paste A: 40.6 wt% spherical Cu powder with an average particle size D50 of 0.3 μm, 5.6 wt% Ba-B-Si glass powder, 5.2 wt% resin obtained by copolymerizing Ethocel resin and acrylic resin, and 48.6 wt% terpineol.

[0055] (Immersion) The external electrode paste was applied to a flat surface using a doctor blade to a thickness of 600 μm. The end surface 13 of the fired laminated chip 10 for forming the multilayer ceramic capacitor 1 having dimensions of 3.2 mm in the longitudinal direction L, 1.6 mm in the lamination direction T, and 1.6 mm in the width direction W was immersed in the applied external electrode paste 160 and pulled up at a speed of 0.1 mm / sec.

[0056] (Re-immersion) Next, in order to adjust the thickness of the external electrode paste 161 attached to the laminated chip sintered body 10, a doctor blade was used to apply the external electrode paste to a flat surface to a thickness of 400 μm, and the end surface 13 of the laminated chip sintered body 10 was again immersed in the applied external electrode paste 160 and pulled up at a speed of 0.1 mm / sec.

[0057] Drying was carried out by placing the sample in an oven heated to 150°C for 10 minutes, and then drying with N ２ The mixture was fired at 700°C in a furnace.

[0058] In the above example, the external electrode paste is immersed twice, the first time to a depth of 600 μm and the second time to a depth of 400 μm, but this is not limited to this and the external electrode paste can be immersed multiple times. Furthermore, the depth of immersion in the external electrode paste 161 is not limited to 600 μm and 400 μm, but it is preferable to gradually decrease the immersion depth in order to remove excess external electrode paste 160 adhering to the end surface 13 of the fired laminated chip body 10.

[0059] The specific method for measuring the film thickness of the external electrodes on the cross sections of the sintered multilayer ceramic capacitor taken along lines AA and BB is as follows.

[0060] The periphery of the multilayer ceramic capacitor 1 was hardened with synthetic resin so that the side surfaces 12 of the laminate 10 were exposed. Next, one of the side surfaces 12 of the laminate 10 was placed downward, and the laminate 10 was polished to a depth where the side surfaces of the internal electrodes 15 exposed on the end surfaces 13 of the laminate 10 began to be exposed. The cross section (cross section along line A-A) was observed using a metallurgical microscope (Olympus BX51M), and the distance in the longitudinal direction L from either end of the internal electrodes 15 located at both ends in the stacking direction T to the surface of the external electrode was measured in six fields of view. The observation magnification was 10x for the eyepiece and 100x for the objective lens. The average of 16.5 μm over the six fields of view was defined as distance a.

[0061] Next, a cross section (cross section along line B-B) polished to the center in the width direction W was observed, and the maximum film thickness of the external electrode 16 in the length direction L at the end face 13 of the laminate 10 was measured in three fields of view. The average of 44.5 μm for the three fields of view was taken as the maximum thickness b of the external electrode.

[0062] The ratio b / a of the maximum thickness b to the distance a, which is an index for evaluating the flatness of the external electrodes, was 2.7.

[0063] (Angle between the main surface of the laminate and the peripheral surface of the external electrode) In the cross section along line B-B, the angle between the main surface 11 of the laminate 10 and the surface of the peripheral portion E of the external electrode 16 was 20.7 degrees on average in six visual fields, and no peeling of the peripheral portion E of the external electrode 16 from the main surface 11 of the laminate 10 was observed in any of the six visual fields.

[0064] (Thickness of external electrode on main surface of laminate) Furthermore, in the cross section along line B-B, the maximum thickness portion of the external electrode 16 on the main surface 11 of the laminate 10 in the stacking direction T was observed using an eyepiece with a magnification of 10x and an objective lens with a magnification of 100x, and the average of six fields of view was 13.8 μm.

[0065] (Evaluation) By adjusting the shape of the external electrode paste 161 applied to the laminated chip sintered body 10 and controlling the convection of the external electrode paste 161 due to the evaporation of the solvent, it became possible to flatten the formed external electrode 16, and it was also possible to suppress peeling of the peripheral portion E of the external electrode 16 during sintering.

[0066] (Comparative Example 1)

[0067] (External electrode paste B) The following raw materials were kneaded in a roll mill to prepare external electrode paste B: 67.8 wt% flat Cu powder with an average particle size D50 of 4 μm 8.3 wt% Ba-B-Si glass powder 6.6 wt% acrylic resin 17.3 wt% Terpineol Note that external electrode paste B is a paste conventionally used for external electrodes of multilayer ceramic capacitors.

[0068] The sintered laminated chip body was immersed and re-immersed in the external electrode paste B, and then left to stand in an oven heated to 150°C for 10 minutes. ２ The mixture was fired at 800°C in a furnace.

[0069] Measurements were carried out in the same manner as in Example 1 on the AA cross section and the BB cross section of the multilayer ceramic capacitor, and the ratio b / a, which is an index for evaluating the flatness of the external electrodes, was found to be 10.3.

[0070] (Angle between the main surface of the laminate and the peripheral surface of the external electrode) Measurement was performed using the same method as in Example 1. As a result, no peeling was observed at the peripheral portion E of the external electrode 16, and the average angle for six fields of view was 20.3 degrees.

[0071] (Thickness of External Electrodes on Main Surfaces of Laminate) Measurement was carried out in the same manner as in Example 1, and the average thickness over six fields of view was 22.8 μm.

[0072] (Evaluation) With external electrode paste B, there was no peeling of the peripheral edge E of the external electrodes 16 on the main surface of the laminate 10, but no flattening phenomenon was observed during solvent evaporation, and thinning of the external electrodes could not be achieved.

[0073] The evaluation results for Example 1 and Comparative Example 1 as well as other Examples and Comparative Examples are shown below.

[0074]

[0075] In order to obtain flat external electrodes with reduced bulging in the central portion C, the index b / a for evaluating the flatness of the external electrodes is preferably 2.8 or less. In order to prevent peeling of the peripheral portion E of the external electrodes on the main surface of the laminate, it is preferable that the thickness of the external electrodes in the lamination direction T is 15.1 μm or less, and the angle formed between the main surface of the laminate and the peripheral surface of the external electrodes is 39.1 degrees or less.

[0076] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various changes and modifications are possible.

[0077] REFERENCE SIGNS LIST 1 Multilayer ceramic capacitor 10 Laminate (laminated chip sintered body) 11 Main surface 11a First main surface 11b Second main surface 12 Side surface 12a First side surface 12b Second side surface 13 End surface 13a First end surface 13b Second end surface 14 Dielectric layer 15 Internal electrode 15a First internal electrode 15b Second internal electrode 16 External electrode 16a First external electrode 16b Second external electrode 141 Outer layer 142 Inner dielectric layer 143 Margin portion 160 External electrode paste 161 External electrode paste attached to laminated chip sintered body C Central portion S Peripheral portion E Peripheral edge portion

Claims

1. A multilayer ceramic capacitor comprising: a laminate in which dielectric layers and internal electrodes are laminated, the laminate having two main surfaces opposing each other in a lamination direction, two side surfaces opposing each other in a width direction intersecting the lamination direction, and two end faces opposing each other in a length direction intersecting the lamination direction and the width direction; and an external electrode formed on an outer surface of the laminate, wherein the dimensions of the laminate are 0.8 mm or more in the lamination direction, 0.8 mm or more in the width direction, and 1.6 mm or more in the length direction, the external electrode contains Cu, the thickness of the external electrode in the lamination direction on the main surface of the laminate is 15 μm or less, an angle formed between the main surface and a peripheral surface of the external electrode on the main surface of the laminate is 39.1 degrees or less, and a maximum thickness b of the external electrode in the length direction when a cross section of the multilayer ceramic capacitor is viewed at the center of the width direction of the multilayer ceramic capacitor, the cross section being defined by the lamination direction and the length direction, a ratio b / a of a distance a in the longitudinal direction from an end of one of the internal electrode layers located at both ends in the lamination direction to a surface of the external electrode, when a cross section of the multilayer ceramic capacitor is viewed in the lamination direction and the longitudinal direction at a position where a side portion of the internal electrode exposed on the end face of the laminate is exposed, to a distance a in the longitudinal direction from the end of either of the internal electrode layers located at both ends in the lamination direction to a surface of the external electrode, the ratio b / a being 2.8 or less.

2. A method for manufacturing a multilayer ceramic capacitor as described in claim 1, comprising applying an external electrode paste to the end faces and main faces of the laminate before firing, the external electrode paste containing a resin in which an ETHOCEL resin and an acrylic resin are copolymerized, Cu having an average particle size D50 of 0.3 μm or less, and glass filler having an average particle size D50 of 1.0 μm or less.

3. A method for producing a multilayer ceramic capacitor according to claim 2, wherein the external electrode paste is applied to the end faces and the main faces of the pre-fired laminate by dipping the laminate in the external electrode paste multiple times.

4. A method for producing a multilayer ceramic capacitor according to claim 3, wherein the substrate is immersed in the external electrode paste a number of times by gradually decreasing the immersion depth.

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