Multilayer Ceramic Capacitors

Abstract

A laminated ceramic capacitor is provided, which has improved adhesion between a base electrode layer and a Cu plated layer. The laminated ceramic capacitor (1) of the present invention comprises: a laminate (2) in which a plurality of internal electrode layers (15) and internal dielectric layers (14) are alternately laminated, the laminate having main surfaces on both sides of a lamination direction, end surfaces on both sides of a length direction intersecting the lamination direction, and side surfaces on both sides of a width direction intersecting the lamination direction and the length direction; and two external electrodes (3) respectively arranged on the end surfaces of the laminate (2), the external electrodes (3) comprising: a base electrode layer (31) comprising a Cu region (31a) mainly composed of Cu and a glass region (31b) mainly composed of Si; and a Cu plated layer (321) arranged outside the base electrode layer (31), the glass region (31b) of the base electrode layer (31) comprising a Cu-containing glass region (31c) containing Cu.

Description

Technical Field

[0001] The present invention relates to a laminated ceramic capacitor. Background Art

[0002] The laminated ceramic capacitor has an external electrode formed on the end surface of a laminated body in which an internal electrode layer and a dielectric layer are laminated. The external electrode includes a base electrode layer and a plating layer. The base electrode layer is formed by applying a paste including Cu and glass and then sintering it. In addition, a Cu plating layer is sometimes formed on the base electrode layer (see Patent Document 1).

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2021-122068 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] Here, the glass of the base electrode layer is difficult to mix with Cu contained in the paste even after sintering, and remains as glass lumps. There is a problem that the glass portion is difficult to adhere to the Cu plating layer formed on the outside of the base electrode layer.

[0008] An object of the present invention is to provide a multilayer ceramic capacitor having improved adhesion between a base electrode layer and a Cu plating layer.

[0009] Means used to solve problems

[0010] In order to solve the above-mentioned problems, the present invention provides a stacked ceramic capacitor, which comprises: a stacked body, which alternately stacks a plurality of internal electrode layers and internal dielectric layers, has main surfaces on both sides of a stacking direction, has end surfaces on both sides of a length direction intersecting the stacking direction, and has side surfaces on both sides of a width direction intersecting the stacking direction and the length direction; and two external electrodes, which are respectively arranged on the end surfaces in the stacked body, and the external electrodes comprise: a base electrode layer, which includes a Cu region with Cu as a main component, and a glass region with Si as a main component; and a Cu plating layer, which is arranged on the outside of the base electrode layer, and the glass region of the base electrode layer includes a Cu-containing glass region containing Cu.

[0011] Effects of the Invention

[0012] According to the present invention, it is possible to provide a multilayer ceramic capacitor having improved adhesion between a base electrode layer and a Cu plating layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1It is a schematic perspective view of a multilayer ceramic capacitor 1 according to the embodiment.

[0014] Figure 2 yes Figure 1 A partial cross-sectional view of the multilayer ceramic capacitor 1 taken along line II-II.

[0015] Figure 3 yes Figure 1 FIG. 1 is a cross-sectional view of the multilayer ceramic capacitor 1 taken along line III-III.

[0016] Figure 4 This is an example of an enlarged image of the cross section of the exposed inner layer portion 11 .

[0017] Figure 5 This is a flowchart for explaining a method for manufacturing the multilayer ceramic capacitor 1 .

[0018] Figure 6 This is a diagram showing a state before the rolling step in which the foundation electrode layer 31 is sintered on the surface of the laminate 2 .

[0019] Figure 7 It shows Figure 6 The laminated body 2 shown is a diagram of a state after being subjected to a roller process.

[0020] Description of Reference Numerals

[0021] P end face;

[0022] Q peripheral face;

[0023] R edge face;

[0024] R1 ridge;

[0025] 1. Multilayer ceramic capacitor;

[0026] 2 laminated body;

[0027] 14 inner dielectric layer;

[0028] 15 internal electrode layer;

[0029] 3 external electrodes;

[0030] 30M Central;

[0031] 30S peripheral;

[0032] 31 base electrode layer;

[0033] 31a Cu region;

[0034] 31b glass area;

[0035] 31c contains Cu glass region;

[0036] 311 Part I;

[0037] 312 Part II;

[0038] 313 Part III;

[0039] 32 coating layer;

[0040] 321Cu plating layer;

[0041] 322Ni plating layer;

[0042] 323Sn plating layer. DETAILED DESCRIPTION

[0043] (Multilayer Ceramic Capacitor 1)

[0044] The following describes a laminated ceramic capacitor 1 according to an embodiment of the present invention. The laminated ceramic capacitor 1 is substantially rectangular and includes a laminate 2 and a pair of external electrodes 3 provided at both ends of the laminate 2. The laminate 2 includes an inner layer portion 11 in which an internal dielectric layer 14 and an internal electrode layer 15 are laminated.

[0045] Regarding the dimensions of the multilayer ceramic capacitor 1 , for example, the width direction W is 0.1 mm to 0.5 mm, the thickness direction is 0.1 mm to 0.6 mm, and the length direction L is 0.3 mm to 1.0 mm.

[0046] In the following description, as terms indicating directions of the multilayer ceramic capacitor 1, in the multilayer ceramic capacitor 1, the direction in which the pair of external electrodes 3 are provided is referred to as the length direction L. The direction in which the internal dielectric layer 14 and the internal electrode layer 15 are stacked is referred to as the stacking direction T. The direction intersecting both the length direction L and the stacking direction T is referred to as the width direction W. It should be noted that in the embodiment, the width direction W is orthogonal to both the length direction L and the stacking direction T. The length direction L of the multilayer ceramic capacitor 1 of the embodiment is longer than the width direction W and the stacking direction T, but the present invention is not limited thereto, and the length direction L may not be longer than the width direction W and the stacking direction T.

[0047] In the following description, among the six outer surfaces of the stacked body 2, a pair of outer surfaces that are opposite to each other in the stacking direction T are referred to as the first principal surface A1 and the second principal surface A2, a pair of outer surfaces that are opposite to each other in the width direction W are referred to as the first side surface B1 and the second side surface B2, and a pair of outer surfaces that are opposite to each other in the length direction L are referred to as the first end surface C1 and the second end surface C2. It should be noted that, when the first principal surface A1 and the second principal surface A2 are described without special distinction, they are collectively described as principal surface A, when the first side surface B1 and the second side surface B2 are described without special distinction, they are collectively described as side surface B, and when the first end surface C1 and the second end surface C2 are described without special distinction, they are collectively described as end surface C.

[0048] (Laminate 2)

[0049] The laminate 2 includes a laminated body piece 10 and side edge portions 21 disposed on both sides of the laminated body piece 10 in the width direction W. The laminated body piece 10 includes an inner layer portion 11 on which an inner dielectric layer 14 and an inner electrode layer 15 are stacked, and two outer layer portions 22 disposed on both sides of the inner layer portion 11 in the stacking direction T.

[0050] The laminate 2 is roughly rectangular, but a certain area including the ridgeline R1 is rounded and curved. The ridgeline R1 is a portion between two surfaces of the laminate 2, i.e., the main surface A and the side surface B, the main surface A and the end surface C, or the side surface B and the end surface C, and also includes the corner between the main surface A, the side surface B and the end surface C.

[0051] (Inner layer portion 11)

[0052] The inner layer portion 11 is a portion where internal dielectric layers 14 and internal electrode layers 15 are alternately stacked along the stacking direction T.

[0053] (Internal Electrode Layer 15)

[0054] The internal electrode layer 15 includes a plurality of first internal electrode layers 15A and a plurality of second internal electrode layers 15B. The first internal electrode layers 15A and the second internal electrode layers 15B are alternately arranged. It should be noted that when the first internal electrode layers 15A and the second internal electrode layers 15B are not particularly distinguished from each other, they are collectively described as the internal electrode layers 15.

[0055] The internal electrode layer 15 contains, for example, Ni (nickel) as a main component. The internal electrode layer 15 may include dielectric particles of the same composition system as the ceramic contained in the internal dielectric layer 14 .

[0056] The first internal electrode layer 15A includes a first opposing portion 15Aa opposing the second internal electrode layer 15B and a first lead portion 15Ab led out from the first opposing portion 15Aa toward the first end surface C1. The end of the first lead portion 15Ab is exposed at the first end surface C1 and is electrically connected to a first external electrode 3A described later.

[0057] The second internal electrode layer 15B includes a second opposing portion 15Ba opposed to the first internal electrode layer 15A, and a second lead portion (not shown) led from the second opposing portion 15Ba to the second end surface C2. The end of the second lead portion is electrically connected to the second external electrode 3B described later. The internal electrode layer 15 stores electric charge between the first opposing portion 15Aa of the first internal electrode layer 15A and the second opposing portion 15Ba of the second internal electrode layer 15B with the internal dielectric layer 14 interposed therebetween, and functions as a capacitor.

[0058] like Figure 3 As shown, in the cross section WT that passes through the center of the stacked body 2 in the width direction W and the stacking direction T, the positional deviation d of the ends of the two first internal electrode layers 15A and the second internal electrode layer 15B that are adjacent to each other in the stacking direction T in the width direction W is preferably 5 μm or less, and more preferably 0.5 μm or less. That is, the ends of the first internal electrode layer 15A and the second internal electrode layer 15B that are adjacent to each other in the stacking direction T in the width direction W are located at approximately the same position in the width direction W, and the positions of the ends are aligned in the stacking direction T.

[0059] The number of internal electrode layers 15 is preferably 10 to 1000. The thickness of the internal electrode layer 15 is preferably 0.3 μm to 0.4 μm, and more preferably 0.3 μm to 0.35 μm.

[0060] The thickness of the internal electrode layer 15 is measured, for example, as follows: First, the LT cross section passing through the center of the multilayer ceramic capacitor 1 is polished to expose the inner layer 11. If necessary, the exposed cross section is etched to remove the conductor layer stretched by polishing.

[0061] Figure 4 1 is an example of an enlarged image of a cross section of the exposed inner layer portion 11. In the enlarged image shown in the figure, for example, a plurality of straight lines La, Lb, Lc, Ld, and Le extending along the stacking direction T are drawn at equal intervals with a pitch S. The pitch S is preferably 5 to 10 times the thickness of the internal electrode layer 15 to be measured. For example, when measuring an internal electrode layer 15 having a thickness of about 1 μm, the pitch S is set to 5 μm.

[0062] Next, the thickness da, db, dc, dd, and de of each internal electrode layer 15 is measured on each of the five straight lines La, Lb, Lc, Ld, and Le. However, on the straight lines La, Lb, Lc, Ld, and Le, when an internal electrode layer 15 is missing and the internal dielectric layers 14 sandwiching the internal electrode layer 15 are connected to each other, or when the enlarged view of the measurement position is unclear, a new straight line is drawn to measure the thickness of the internal electrode layer 15.

[0063] Moreover, for internal electrode layers 15 having more than 5 layers, for example, internal electrode layers 15 having about 5 layers, the thickness is measured by the above-mentioned method. When the number of stacked internal electrode layers 15 is less than 5 layers, the thickness of all internal electrode layers 15 is measured by the above-mentioned method, and the average value thereof is set as the average thickness of the multiple internal electrode layers 15.

[0064] (Internal dielectric layer 14)

[0065] The internal dielectric layer 14 is, for example, a dielectric ceramic containing Ba and Ti components and containing Si. Alternatively, a material obtained by adding a component having a smaller content than the main component, such as a Mn compound, a Fe compound, a Cr compound, a Co compound, or a Ni compound, to these components may be used.

[0066] The total number of the inner dielectric layer 14 and the outer layer portion 22 is preferably 100 or more and 2000 or less.

[0067] The internal dielectric layer 14 is preferably 0.4 μm or more and 0.5 μm or less, and more preferably 0.4 μm or more and 0.45 μm or less. It should be noted that, as described above, similarly to the internal electrode layer 15, the thickness Da, Db, Dc, Dd, and De of each internal dielectric layer 14 can be measured on each of the five straight lines La, Lb, Lc, Ld, and Le and averaged to thereby determine the thickness of the internal dielectric layer 14.

[0068] (Outer layer 22)

[0069] The outer layer portion 22 is a dielectric layer located on both main surface A sides of the laminate 2 .

[0070] (Side edge portion 21)

[0071] The side edge 21 is disposed on both side B sides of the laminated body small piece 10, i.e., both side B sides of the outer layer portion 22 and the inner layer portion 11, and covers the side B sides of the outer layer portion 22 and the inner layer portion 11. The side edge 21 is a certain width range on the side B side of the laminated body small piece 10.

[0072] The side edge portion 21 of the embodiment is a one-layer structure in the embodiment, but is not limited thereto, and may also be a plurality of layers of two or more layers. It should be noted that when the side edge portion 21 is a plurality of layers, it can be confirmed that it is a plurality of layers in the dark field of an optical microscope, and it can also be determined that it is a plurality of layers by additives segregated between layers.

[0073] The thickness of the side edge portion 21 is preferably 5 μm or more and 20 μm or less. That is, the distance from the end of the internal electrode layer 15 in the width direction W to the side surface B of the laminate is preferably 5 μm or more and 20 μm or less.

[0074] (External electrode 3)

[0075] The external electrode 3 includes a first external electrode 3A provided on the first end surface C1 of the stacked body 2 and a second external electrode 3B provided on the second end surface C2 of the stacked body 2. It should be noted that when the first external electrode 3A and the second external electrode 3B are not particularly distinguished, they are collectively described as the external electrode 3.

[0076] As described above, the end of the first lead portion 15Ab of the first internal electrode layer 15A is exposed at the first end surface C1 and is electrically connected to the first external electrode 3A. In addition, the end of the second lead portion of the second internal electrode layer 15B is exposed at the second end surface C2 and is electrically connected to the second external electrode 3B. Thus, a structure in which a plurality of capacitor elements are electrically connected in parallel is formed between the first external electrode 3A and the second external electrode 3B.

[0077] The external electrode 3 includes a base electrode layer 31 and a plating layer 32 disposed on the base electrode layer 31. The plating layer 32 includes a Cu (copper) plating layer 321 disposed on the base electrode layer 31, a Ni (nickel) plating layer 322 disposed on the Cu plating layer 321, and a Sn (tin) plating layer 323 disposed on the Ni plating layer 322.

[0078] like Figure 2 As shown, the external electrode 3 covers not only the end surface C but also a part of the end surface C side of the main surface A and the side surface B. Specifically, the external electrode 3 includes not only the end surface P arranged at the end surface C, but also the peripheral surface Q arranged at the main surface A and the side surface B, and the edge surface R arranged between the end surface P and the peripheral surface Q in the whole including the base electrode layer 31 and the plated layer 32 and in the base electrode layer 31, the Cu plated layer 321, the Ni plated layer 322, and the Sn plated layer 323 as the plated layer 32. The edge surface R is a portion of the outer side of the curved surface with roundness in the laminate 2, and the curved surface is a surface including the edge line R1 between the end surface C and the main surface A and between the end surface C and the side surface B, and the edge line R1 includes a corner.

[0079] The outer electrode 3 has a peripheral portion 30S that surrounds a central portion 30M that is the center in the stacking direction T and the center in the width direction W, and protrudes outward from the central portion 30M in the entirety including the base electrode layer 31 and the plating layer 32 and also in the base electrode layer 31 alone. When the thickness of the central portion 30M is L1 and the thickness of the peripheral portion 30S is L2, L1<L2. Preferably, L1 is 3 μm or more and 15 μm or less, and L2 is 5 μm or more and 20 μm or less.

[0080] (Central 30M)

[0081] The central portion 30M is the thinnest portion of the end surface P disposed on the end surface C in the entire external electrode 3 and in the base electrode layer 31 alone. The central portion 30M may not be a single point, but may be a certain range including the center in the stacking direction T and the center in the width direction W.

[0082] (Outer periphery 30S)

[0083] The peripheral portion 30S is the thickest portion disposed at the end surface P of the end surface C in the entire external electrode 3 and in the base electrode layer 31 alone. The peripheral portion 30S surrounds both sides of the central portion 30M in the stacking direction T and the width direction W in a substantially rectangular shape on the inner side of the end surface C at a distance T1 from the main surface A in the stacking direction T and the inner side of the side surface B in the width direction W. The peripheral portion 30S is the highest portion along the ridge line of the protrusion that protrudes from the central portion 30M in the end surface C. The distance T1 is preferably 5 μm or more and 20 μm or less, and more preferably 15 μm.

[0084] In addition, if Figure 2 As shown, the outer peripheral portion 30S is arranged closer to the center in the stacking direction T than the internal electrode layer 15 closest to the main surface A side.

[0085] (Base electrode layer 31)

[0086] The base electrode layer 31 is a so-called baked electrode that is fired after the steps of applying and drying the conductive paste described below three times in the embodiment. It should be noted that the base electrode layer 31 is fired simultaneously with the internal electrode layer 15 in the embodiment, but is not limited to this, and may also be fired after the internal electrode layer 15 is fired.

[0087] As described above, the outer peripheral portion 30S surrounding the central portion 30M, which is the center in the stacking direction T and the center in the width direction W, of the base electrode layer 31 protrudes further than the central portion 30M.

[0088] The base electrode layer 31 includes an end surface portion P disposed on the end surface C, an outer peripheral surface portion Q disposed on the main surface A and the side surface B, and an edge surface portion R disposed between the end surface portion P and the outer peripheral surface portion Q.

[0089] In addition, the portion of the base electrode layer 31 arranged on the outer peripheral surface Q includes, in order from the end surface C side toward the center of the length direction L, a first portion 311 of a first thickness t1, a second portion 312 of a second thickness t2, and a third portion 313 of a third thickness t3, and t1>t2>t3.

[0090] Therefore, in the portion of the base electrode layer 31 arranged in the outer peripheral surface portion Q, a step is provided between the first portion 311 and the second portion 312 , and between the second portion 312 and the third portion 313 .

[0091] Furthermore, the length of the first portion 311 in the longitudinal direction L is m1, the length of the second portion 312 in the longitudinal direction L is m2, and the length of the third portion 313 in the longitudinal direction L is m3, and m2 is shorter than m3 and m1.

[0092] That is, the second portion 312 having the shortest length in the longitudinal direction L and located at the center of the step is surrounded by the first portion 311 and the third portion 313 having the long length in the longitudinal direction L via the step.

[0093] in addition, Figure 3 In the illustrated base electrode layer 31 , a length W1 of the first portion 311 in the width direction W is 1.01 times or more the length W2 of the second portion 312 in the width direction W.

[0094] Furthermore, as described above, the third portion 313 in the base electrode layer 31 has a thickness t3 , but has a thin region V at the boundary with the second portion 312 .

[0095] The base electrode layer 31 includes a Cu region 31 a mainly composed of Cu and a glass region 31 b mainly composed of Si. The glass region 31 b includes a Cu-containing glass region 31 c containing Cu.

[0096] The Cu-containing glass region 31c exists on the outer surface side of the base electrode layer 31, that is, on the side of the Cu plating layer 321. The Cu-containing glass region 31c is a region where Cu enters the Si low-density glass region, and the Si density of the Si low-density glass region is lower than that of the glass region 31b on the end surface C side in the base electrode layer 31.

[0097] The Cu region 31a with Cu as the main component and the glass region 31b with Si as the main component can be detected by EDX analysis (energy dispersive X-ray analysis). The region where silicon dioxide (glass) is detected by EDX analysis is set as the glass region 31b with Si as the main component. In addition, in the region detected as the glass region 31b, the region where Si is low-density and Cu is also detected is set as the Si low-density glass region and the Cu-containing glass region 31c.

[0098] The glass region 31 b of the second portion 312 of the portion of the base electrode layer 31 arranged on the outer peripheral surface Q of the base electrode layer 31 protrudes from the surface and sinks into a Cu plating layer 321 to be described below arranged outside the base electrode layer 31 .

[0099] (Cu plating layer 321)

[0100] The Cu plating layer 321 is formed on the outer side of the base electrode layer 31 so as to cover the surface of the base electrode layer 31 .

[0101] The Cu plating layer 321 is used to prevent a portion of hydrogen generated in the Ni electrolytic plating process of forming the Ni plating layer 322 on the Cu plating layer 321 from entering the interior of the laminated body 2 through the base electrode layer 31 and reaching the internal electrode layer 15. As a result, the hydrogen content in the laminated ceramic capacitor 1 can be reduced, so that the diffusion of hydrogen into the internal dielectric layer 14 can be suppressed, thereby preventing the degradation of the insulation resistance.

[0102] As described above, the base electrode layer 31 and the Cu plated layer 321 include the end surface P arranged on the end surface C, the peripheral surface Q arranged on the main surface A and the side surface B, and the edge surface R arranged between the end surface P and the peripheral surface Q.

[0103] The thickness of the central portion 30M of the portion of the Cu plating layer 321 extending along the end surface C is set to c1, and the thickness of the thinnest portion in the edge surface R is set to c2. The thickness of the central portion 30M of the portion of the base electrode layer 31 extending along the end surface C is set to u1, and the thickness of the thinnest portion in the edge surface R is set to u2. In this case, c1-c2<u1-u2. It should be noted that the Cu plating layer 321 gradually becomes thinner at the front end of the peripheral surface Q, but most of the other parts have a roughly constant thickness, so the thicknesses c1 and c2 are roughly constant.

[0104] In addition, the thickness u2 of the edge surface portion R of the base electrode layer 31 is thinner than the thickness c2 of the edge surface portion R of the Cu plating layer 321 .

[0105] The edge surface R of the base electrode layer 31 tends to be thinned by grinding in the roller process described later. When the base electrode layer 31 becomes thinner, the moisture resistance deteriorates. However, in the embodiment, the Cu plating layer 321 is attached with a substantially uniform thickness over the entire range, thereby ensuring the sealing performance.

[0106] The thickness of the base electrode layer 31 decreases sharply when it becomes closer to the outer side than the peripheral portion 30S of the thickness L2, and the thickness u2 of the thinnest portion in the edge surface R becomes thinner than the thickness c2 of the Cu plating layer 321. It should be noted that "thickness" refers to the length of the normal drawn from the inner interface of each layer to the outer interface.

[0107] (Ni plating layer 322)

[0108] The Ni plating layer 322 is formed on the outer side of the Cu plating layer 321 so as to cover the surface of the Cu plating layer 321. The thickness of the Ni plating layer 322 is not particularly limited, and is, for example, 3 μm to 5 μm.

[0109] The Ni plated layer 322 prevents the base electrode layer 31 and the Cu plated layer 321 from being corroded by solder when the multilayer ceramic capacitor 1 is mounted.

[0110] (Sn plating layer 323)

[0111] The Sn plating layer 323 is formed on the outer side of the Ni plating layer 322 so as to cover the surface of the Ni plating layer 322. The thickness of the Sn plating layer 323 is not particularly limited, and is, for example, 3 μm to 5 μm.

[0112] The Sn plating layer 323 can improve the wettability of solder when mounting the multilayer ceramic capacitor, thereby facilitating mounting.

[0113] It should be noted that the thickness L1 of the central portion 30M and the thickness L2 of the peripheral portion 30S in the external electrode 3, the distance T1 of the peripheral portion 30S from the periphery of the end surface C, the first thickness t1 of the first portion 311, the second thickness t2 of the second portion 312, the third thickness t3 of the third portion 313, the length m3 of the third portion 313, the length m2 of the second portion 312, the length m1 of the first portion 311, the length W1 of the first portion 311, the length W2 of the second portion 312, the thickness u1 of the central portion 30M, the thickness u2 of the edge portion R, the thickness c1 of the central portion 30M in the Cu plated layer 321, the thickness c2 of the edge portion R, the thickness of the Ni plated layer 322, the thickness of the Sn plated layer 323, etc. can be measured in the same way as the method for measuring the thickness of the internal electrode layer 15.

[0114] Specifically, the measurement can be performed by polishing multilayer ceramic capacitor 1 to expose a predetermined cross section, magnifying the section with a microscope or the like, measuring the lengths of a plurality of locations, and averaging the results.

[0115] In addition, the step difference between the first portion 311 and the second portion 312, the step difference between the second portion 312 and the third portion 313, etc. in the base electrode layer 31 can also be detected by appearance. The protruding glass region in the second portion 312 can also be detected by grinding the cross section to expose the cross section and enlarge the image.

[0116] (Method for Manufacturing Multilayer Ceramic Capacitor 1)

[0117] (Raw material sheet production process S1)

[0118] Figure 5 This is a flowchart for explaining a method for manufacturing the multilayer ceramic capacitor 1 .

[0119] First, a ceramic slurry for an inner dielectric layer containing ceramic powder containing Ba and Ti components, a binder, a solvent, and Si is prepared.

[0120] The ceramic slurry is formed into a sheet on a carrier film using a die coater, a gravure coater, a micro gravure coater, or the like to produce a ceramic green sheet.

[0121] Next, a conductive paste containing Ni is printed on the ceramic green sheet so as to have a stripe-shaped pattern by screen printing, inkjet printing, gravure printing, etc., thereby forming a conductive pattern. Thus, a raw material sheet is prepared in which a conductive pattern to become the internal electrode layer 15 is printed on the surface of the ceramic green sheet for the internal dielectric layer to become the internal dielectric layer 14.

[0122] In addition, similarly to the ceramic slurry for the inner dielectric layer, a ceramic slurry for the outer layer portion containing ceramic powder containing Ba and Ti components, a binder, a solvent, and Si is prepared. The ceramic slurry for the outer layer portion is formed into a sheet on a carrier film using a die coater, a gravure coater, a micro gravure coater, etc. to produce a ceramic green sheet for the outer layer portion.

[0123] (Lamination Step S2)

[0124] Next, a plurality of raw material sheets are stacked. At this time, the plurality of raw material sheets are stacked so that the band-shaped conductive patterns face the same direction and the band-shaped conductive patterns are offset by half a pitch between adjacent raw material sheets in the width direction W. Furthermore, ceramic green sheets for the outer layer portion 22 are stacked on both sides of the plurality of stacked raw material sheets.

[0125] (Step S4 of pasting ceramic green sheets on side edges)

[0126] A ceramic slurry for the side edge portion containing ceramic powder containing Ba and Ti components, a binder, a solvent, and Si is prepared. The ceramic slurry for the side edge portion is applied to the surface of the carrier film and dried to produce a ceramic green sheet for the side edge portion. Thereafter, the ceramic green sheet for the side edge portion is peeled off from the carrier film and placed opposite to the side B of the laminated body small piece 10. The ceramic green sheet for the side edge portion is adhered to the side B of the laminated body small piece 10 by pressing and impacting, thereby producing a laminated body 2 before firing.

[0127] (Base electrode material coating step S5)

[0128] The base electrode paste is applied to both end surfaces C of the laminate 2 in which the ceramic green sheets for the side edge portions are bonded to the laminate small pieces 10 .

[0129] (Paste for base electrode)

[0130] The base electrode paste is a conductive paste including metal powder as Cu powder, glass, a resin, and a solvent, wherein the resin includes at least a part of a copolymerized ethyl cellulose-based resin and an acrylic-based resin.

[0131] The Cu powder is particles containing at least one of Cu and a Cu alloy.

[0132] The glass contains Si and is in a frit form.

[0133] The ethyl cellulose-based resin is, for example, at least one of ethyl cellulose, methyl cellulose, hydroxypropyl cellulose, trityl cellulose, acetyl cellulose, carboxymethyl cellulose, and nitrocellulose.

[0134] 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.

[0135] The solvent includes, for example, at least one of terpineol, dihydroterpineol, dihydroterpineol acetate, propylene glycol phenyl ether, benzyl alcohol, texanol, and butyl carbitol acetate.

[0136] At least a part of the ethyl cellulose resin and the acrylic resin is copolymerized. As one example, the OH group of the ethyl cellulose resin is replaced with a vinyl group, and the ethyl cellulose resin and the acrylic resin are bonded via the replaced vinyl group.

[0137] The base electrode layer 31 is formed by repeating three times in the embodiment a process of immersing both end surfaces C of the laminate 2 in the base electrode paste, then pulling them up and drying them.

[0138] Here, the base electrode paste applied to the stacked body 2 is thinner at the end than at the center, so the drying of the end is easy to progress. Therefore, the proportion of the resin in the external electrode paste is higher at the end than at the center, and it becomes unstable in energy, so that the so-called Marangoni convection occurs in which the external electrode paste flows from the center to the end.

[0139] Ethyl cellulose resin is rigid and has high heat storage capacity. Therefore, in the drying process, it suppresses the external electrode paste from solidifying in the middle of the flow, which plays a role in promoting Marangoni convection. Therefore, by adjusting the amount of ethyl cellulose resin, the intensity of Marangoni convection can be adjusted so that the external electrode paste becomes a shape protruding from the periphery of the end face C when drying. In this protruding shape, a portion corresponds to the peripheral portion 30S. In this way, by adjusting the amount of ethyl cellulose resin, the thickness L1 of the central portion 30M and the thickness L2 of the peripheral portion 30S can be adjusted, and can be adjusted to L1<L2. In addition, by adjusting the amount of ethyl cellulose resin, the distance T1 between the peripheral portion 30S and the periphery of the end face C can also be adjusted.

[0140] In addition, in the embodiment, when the process of dipping both end faces C of the stacked body 2 in the base electrode paste and then lifting and drying is repeated three times, the third portion 313 is formed in the first dipping. The dipping depth at this time is m1+m2+m3. Then, when the second dipping is performed, the dipping depth is shallower than the first dipping by m3. Moreover, when the third dipping is performed, the dipping depth is shallower than the second dipping by m2. m2 is shorter than m3 and m1.

[0141] Thus, the third portion 313 having a length m3 in the longitudinal direction L, the second portion 312 having a length m2 in the longitudinal direction L, and the first portion 311 having a length m1 in the longitudinal direction L are formed.

[0142] Furthermore, the first portion 311 having the first thickness t1, the second portion 312 having the second thickness t2, and the third portion 313 having the third thickness t3 are sequentially arranged in the outer peripheral portion Q of the base electrode layer 31 from the end surface C side toward the center portion in the longitudinal direction L, and t1>t2>t3 is satisfied. Furthermore, the base electrode layer 31 in the outer peripheral portion Q forms a step difference between the first portion 311 and the second portion 312 and between the second portion 312 and the third portion 313.

[0143] (Firing Step S6)

[0144] After drying, the laminate 2 to which the base electrode paste is attached is subjected to a degreasing treatment in a nitrogen atmosphere under predetermined conditions, and then fired at a predetermined temperature in a nitrogen-hydrogen-water vapor mixed atmosphere to be sintered.

[0145] At this time, by adjusting the firing conditions and the amount of Cu powder, solvent, resin, glass, etc. contained in the base electrode paste, the glass region 31 b is floated on the surface of the base electrode layer 31 .

[0146] Figure 6 1 is a diagram showing a state before the rolling process in which the base electrode layer 31 is sintered on the surface of the laminate 2. Figure 6 In the illustrated state, the glass region 31 b is in a state of floating on the surface of the base electrode layer 31 .

[0147] The circle equivalent diameter of the glass region 31b is preferably 1 μm or less. This is because if it exceeds 1 μm, it will take a long time to grow the Cu plating in the subsequent Cu plating process. On the other hand, if it is 0.5 μm or less, sealing performance cannot be expected.

[0148] (Rolling process S7)

[0149] In the subsequent roller step S7 , for example, a roller treatment is performed in which the laminate 2 having the base electrode layer 31 and the medium are stirred in a stirring tank so that the surface of the base electrode layer 31 is polished while the medium collides with the surface of the base electrode layer 31 . Figure 7 It shows Figure 6 The laminated body 2 shown is a diagram of a state after being subjected to a roller process.

[0150] When the dielectric collides with the surface of the base electrode layer 31, the glass region 31b protruding from the surface of the base electrode layer 31 becomes flat except for the second portion 312, and the Cu region 31a is stretched, so that the surface of the base electrode layer 31 becomes smooth. Figure 7 The glass region 31b indicated by the middle reference numeral 31bb is a glass region 31bb which protrudes from the surface of the base electrode layer 31 before the roller step S7 but is flattened by polishing with the medium.

[0151] exist Figure 7 The dashed line 31A is Figure 6 31B shown by the solid line is the outline of the base electrode layer 31A after the roller treatment. As shown in the figure, during the roller treatment, the outer periphery of the base electrode layer 31 is polished by the medium. However, in the embodiment, Figure 6 In the state before the roller treatment shown, the periphery of the end surface C of the base electrode layer 31A is in a protruding shape. In the roller step S7, the periphery of the end surface C of the base electrode layer 31 is particularly easy to be scraped off, but since the periphery is protruding, the possibility of scraping off the entire base electrode layer 31 is low, and the laminate 2 is not exposed.

[0152] In addition, the length m2 of the second portion 312 is shorter than that of the first portion 311 and the third portion 313, and the second portion 312 is surrounded by the first portion 311 and the third portion 313 due to the step difference. Therefore, the surface of the second portion 312 is unlikely to collide with the medium, and the glass region 31b protruding from the surface of the second portion 312 maintains the state of protruding from the surface. Figure 7 The glass region 31b indicated by the middle mark 31ba is the glass region 31ba that remains protruding from the surface of the base electrode layer 31 even after the roller step S7. In this way, many glass regions 31ba that remain protruding from the surface remain on the surface of the second portion 312, so that the surface hardness remains high and the bending strength of the multilayer ceramic capacitor 1 increases.

[0153] (Cu plating layer forming step S8)

[0154] Next, a Cu plated layer 321 is formed on the base electrode layer 31. Here, the glass region 31b exposed on the surface of the base electrode layer 31, whether it is the glass region 31bb that becomes flat in the roller step S7 or the glass region 31ba that remains exposed from the surface like the second portion 312 of the peripheral surface Q, contains Si at a density equal to that of the glass region 31b contained in the inside of the base electrode layer 31 before Cu plating.

[0155] However, in the Cu plating layer forming step S8 , part of the plating solution corrodes the glass region 31 ba and the glass region 31 bb on the surface of the base electrode layer 31 .

[0156] Therefore, the density of glass, i.e., Si, contained in the glass regions 31ba and 31bb on the surface of the base electrode layer 31 decreases, and a plurality of cavities are generated to form Si low-density glass regions. Cu contained in the Cu plating solution enters the cavities, and the Si low-density glass regions become Cu-containing glass regions 31c.

[0157] In this way, Cu contained in the Cu plating solution enters the glass region 31ba and the glass region 31bb which become the Si low-density glass region, thereby improving the bonding strength between the base electrode layer 31 and the Cu plating layer 321. Therefore, the Cu plating layer 321 can completely cover the base electrode layer 31 without a gap, and high sealing can be obtained.

[0158] In addition, the glass region 31ba on the surface of the second portion 312 is also difficult to be polished in the roller step S7 and remains protruding from the Cu region. Therefore, it sinks into the Cu plating layer 321, and thus the adhesion with the Cu plating layer 321 is improved.

[0159] (Ni plating layer forming step S9)

[0160] Next, the Ni plating layer 322 is formed outside the Cu plating layer 321 so as to cover the surface of the Cu plating layer 321. The Ni plating layer 322 can prevent the base electrode layer 31 and the Cu plating layer 321 from being corroded by solder when the multilayer ceramic capacitor 1 is mounted.

[0161] (Sn plating layer forming step S10)

[0162] Sn plating layer 323 is formed outside Ni plating layer 322 so as to cover the surface of Ni plating layer 322. Sn plating layer 323 can improve the wettability of solder when mounting the multilayer ceramic capacitor, and facilitate mounting.

[0163] As mentioned above, although embodiment of this invention was described, it is not limited to this embodiment, Various deformation|transformation is possible within the range of the summary.

Claims

1. A multilayer ceramic capacitor comprising: A laminate having a plurality of internal electrode layers and internal dielectric layers alternately laminated, having main surfaces on both sides of a lamination direction, end surfaces on both sides of a length direction intersecting the lamination direction, and side surfaces on both sides of a width direction intersecting the lamination direction and the length direction; and two external electrodes, which are respectively arranged on the end surfaces of the stacked body, The external electrode comprises: a base electrode layer including a Cu region mainly composed of Cu and a glass region mainly composed of Si; and A Cu plating layer is arranged on the outer side of the base electrode layer, The glass region of the base electrode layer includes a Cu-containing glass region containing Cu, The Cu-containing glass region containing Cu is a region into which the Cu plating layer enters.

2. The multilayer ceramic capacitor according to claim 1, wherein The base electrode layer and the Cu plating layer include: An end surface portion, which is disposed on the end surface; an outer peripheral surface portion disposed on the main surface and the side surface; and an edge portion arranged on a curved surface including an edge line portion between the end surface and the main surface and an edge line portion between the end surface and the side surface, The thinnest portion of the Cu plating layer disposed on the end surface has a thickness of c1, and the thinnest portion of the Cu plating layer on the edge surface has a thickness of c2. The thinnest portion of the base electrode layer disposed on the end surface has a thickness u1, and the thinnest portion of the base electrode layer on the edge surface has a thickness u2. At this time, c1-c2<u1-u2.

3. The multilayer ceramic capacitor according to claim 2, wherein: A thickness u2 of the thinnest portion in the edge surface portion of the base electrode layer is thinner than a thickness c2 of the thinnest portion in the edge surface portion of the Cu plating layer.

4. The multilayer ceramic capacitor according to any one of claims 1 to 3, wherein The glass region of the base electrode layer disposed on the Cu plating layer side is a Si low-density glass region having a lower Si density than the glass region disposed on the end surface side.

5. The multilayer ceramic capacitor according to claim 4, wherein: The Si low-density glass region is the Cu-containing glass region.

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