Multilayer ceramic electronic component and method for manufacturing the same

Abstract

To provide a laminated ceramic electronic component capable of suppressing diffusion of copper of an external electrode to an internal electrode.SOLUTION: A multi-layer ceramic electronic component includes a body in which internal electrodes containing nickel as a main component and dielectric layers containing ceramic as a main component are alternately laminated in a first direction and which has a pair of end surfaces from which the internal electrodes are alternately exposed and which face each other in a second direction, and a pair of external electrodes in contact with the exposed internal electrodes and containing copper as a main component. A molar ratio of copper to nickel in the first internal electrode in an end margin region including the first internal electrode exposed to the one end surface and not including the second internal electrode exposed to the other end surface is larger than a molar ratio of copper to nickel in the first internal electrode in a capacity region in which the first internal electrode and the second internal electrode overlap each other in a central portion in the second direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a multilayer ceramic electronic component and a method for manufacturing the same. [Background technology]

[0002] In multilayer ceramic electronic components such as multilayer ceramic capacitors having internal electrodes mainly composed of nickel and external electrodes mainly composed of copper, it is known that the molar ratio of copper in the internal electrodes on the main surface side is made higher than the copper concentration in the internal electrodes in the center (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-15925 Summary of the Invention [Problem to be solved by the invention]

[0004] If copper from the external electrodes diffuses into the internal electrodes and the copper reacts with nickel, the internal electrodes may expand and cracks may occur in the element.

[0005] The present invention has been made in view of the above-mentioned problems, and has as its object to provide a multilayer ceramic electronic component that can suppress the diffusion of copper from external electrodes into internal electrodes, and a method for manufacturing the same. [Means for solving the problem]

[0006] The present invention is a multilayer ceramic electronic component comprising: an element body in which a plurality of internal electrodes primarily composed of nickel and a plurality of dielectric layers primarily composed of ceramic are alternately stacked in a first direction, the stacked internal electrodes being alternately exposed and having a pair of end faces facing each other in a second direction; and a pair of external electrodes in contact with the plurality of internal electrodes exposed from the pair of end faces, respectively, the layers in contact with the plurality of internal electrodes being primarily composed of copper; wherein the molar ratio of copper to nickel in the first internal electrodes in an end margin region, which is an end portion of the element body in the second direction as viewed from the first direction, and which includes a first internal electrode of the plurality of internal electrodes exposed on one of the pair of end faces and does not include a second internal electrode exposed on the other of the pair of end faces, is greater than the molar ratio of copper to nickel in the first internal electrodes in a capacity region, which is a central portion of the element body in the second direction as viewed from the first direction, where the first internal electrodes and the second internal electrodes overlap each other.

[0007] In the above configuration, within the capacitance region, the molar ratio of copper to nickel of the internal electrode located outermost in the first direction among the plurality of internal electrodes can be greater than the molar ratio of copper to nickel of the internal electrode located in the center in the first direction.

[0008] In the above configuration, within the capacitance region, the molar ratio of copper to nickel at the ends of the internal electrodes in a third direction that is approximately perpendicular to the first direction and the second direction can be greater than the molar ratio of copper to nickel at the center of the internal electrodes in the third direction.

[0009] The present invention provides a method for manufacturing a multilayer ceramic electronic component, including the steps of: preparing an element body in which a plurality of internal electrodes primarily composed of nickel and a plurality of dielectric layers primarily composed of ceramic are alternately stacked in a first direction, the stacked internal electrodes having a pair of end faces that are alternately exposed and facing each other in a second direction; wherein the molar ratio of copper to nickel of the first internal electrodes in an end margin region, which is an end portion of the element body in the second direction as viewed from the first direction and includes a first internal electrode of the plurality of internal electrodes exposed at one of the pair of end faces and does not include a second internal electrode exposed at the other of the pair of end faces, is larger than the molar ratio of copper to nickel of the first internal electrodes in a capacity region, which is a central portion of the element body in the second direction as viewed from the first direction and where the first internal electrodes and the second internal electrodes overlap each other; and forming a pair of external electrodes that are in contact with the plurality of internal electrodes exposed from the pair of end faces, respectively, and in which layers that contact the plurality of internal electrodes are primarily composed of copper.

[0010] In the above configuration, the process of forming the pair of external electrodes can include a process of applying a metal paste so as to contact each of the multiple internal electrodes exposed from the pair of end faces, and a process of baking the applied metal paste.

[0011] In the above configuration, the process of preparing the element body can include a process of preparing a laminated sheet in which the molar ratio of copper to the main component metal elements of the ceramic of a dielectric pattern provided in the end margin region so as to contact the second internal electrode in the second direction is greater than the molar ratio of copper to the main component metal elements of the ceramic of a green sheet overlaid on the first internal electrode and the second internal electrode in the first direction, and a process of firing the laminated sheet.

[0012] In the above configuration, before the step of forming the external electrode, the molar ratio of copper to nickel of the internal electrode located outermost in the first direction among the plurality of internal electrodes within the capacity region can be configured to be greater than the molar ratio of copper to nickel of the internal electrode located in the center in the first direction.

[0013] In the above configuration, before the step of forming the external electrode, within the capacitance region, the molar ratio of copper to nickel at the end of the internal electrode in a third direction that is approximately perpendicular to the first direction and the second direction can be configured to be greater than the molar ratio of copper to nickel at the center of the internal electrode in the third direction. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a multilayer ceramic electronic component that can suppress the diffusion of copper from the external electrodes into the internal electrodes, and a method for manufacturing the same. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a partial cross-sectional perspective view of a multilayer ceramic capacitor according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line BB in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line CC in FIG. [Figure 5] FIG. 5 is a cross-sectional view taken along line DD in FIG. [Figure 6] FIG. 6 is a flowchart showing a method for manufacturing a multilayer ceramic capacitor according to an embodiment. [Figure 7] FIG. 7(a) is a plan view showing the method for manufacturing the multilayer ceramic capacitor according to the embodiment, and FIG. 7(b) is a cross-sectional view taken along line AA in FIG. 7(a). [Figure 8] FIG. 8 is a cross-sectional view illustrating a method for manufacturing a multilayer ceramic capacitor according to an embodiment. [Figure 9] FIG. 9 is a cross-sectional view illustrating a method for manufacturing a multilayer ceramic capacitor according to an embodiment. [Figure 10] 10(a) and 10(b) are cross-sectional views illustrating a method for manufacturing the multilayer ceramic capacitor according to the embodiment. [Figure 11] FIG. 11 is a cross-sectional view of a comparative multilayer ceramic capacitor. [Figure 12] FIG. 12 is a cross-sectional view of a comparative multilayer ceramic capacitor. [Figure 13] 13(a) and 13(b) are schematic diagrams showing the molar ratio of copper in the internal electrodes. [Figure 14] 14(a) and 14(b) are schematic diagrams showing the molar ratio of copper in the internal electrodes. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, with reference to the drawings, an embodiment will be described using a multilayer ceramic capacitor as an example of a multilayer ceramic electronic component.

[0017] (Embodiment) Fig. 1 is a partial cross-sectional perspective view of a multilayer ceramic capacitor 100 according to an embodiment. Fig. 2 is a cross-sectional view taken along line AA in Fig. 1. Fig. 3 is a cross-sectional view taken along line BB in Fig. 1. Fig. 4 is a cross-sectional view taken along line CC in Fig. 1. Fig. 5 is a cross-sectional view taken along line DD in Fig. 1. In Figs. 2 to 5, the first portion 13a of the internal electrodes 12a and 12b is indicated by hatching with one type of parallel lines, and the second portion 13b is indicated by cross-hatching with two types of parallel lines crossing each other.

[0018] 1 to 5, the Z direction (first direction) is the stacking direction in which the dielectric layers 14 and the internal electrodes 12a and 12b are stacked, and is the direction in which the bottom surface 55 and top surface 56 of the element body 10 face each other. The X direction (second direction) is the length direction of the element body 10, and is the direction in which the pair of end surfaces 51 and 52 of the element body 10 face each other. The Y direction (third direction) is the width direction of the element body 10 and the internal electrodes 12a and 12b, and is the direction in which the pair of side surfaces 53 and 54 of the element body 10 face each other. The X direction, Y direction, and Z direction are approximately perpendicular to each other.

[0019] The multilayer ceramic capacitor 100 includes a substantially rectangular parallelepiped element body 10 and external electrodes 20a and 20b. The element body 10 includes a multilayer body 11 and side dielectric layers 18a and 18b provided on both sides of the multilayer body 11 in the Y direction.

[0020] The laminate 11 has a plurality of dielectric layers 14, a plurality of internal electrodes 12a and 12b, and cover dielectric layers 16a and 16b. The plurality of internal electrodes 12a and the plurality of internal electrodes 12b are alternately stacked. The internal electrode 12a is extended to one end face 51, and the internal electrode 12b is extended to the other end face 52. One of the plurality of dielectric layers 14 is provided between one of the plurality of internal electrodes 12a and one of the plurality of internal electrodes 12b. The internal electrodes 12a and 12b form the outermost layers of the laminate 11 in the stacking direction (Z direction), and the bottom and top surfaces of the laminate 11 are covered by cover dielectric layers 16a and 16b, respectively. The internal electrodes 12a and 12b are examples of first and second internal electrodes.

[0021] The regions of the internal electrodes 12a and 12b are divided into a first portion 13a and a second portion 13b. The copper concentration in the second portion 13b is higher than that in the first portion 13a. The copper concentration is expressed as the molar ratio of copper to nickel, which is the main metallic element of the internal electrodes 12a and 12b. Hereinafter, this may also be simply referred to as the copper molar ratio.

[0022] The internal electrodes 12a and 12b are alternately exposed on the end faces 51 and 52. The internal electrode 12a is exposed but the internal electrode 12b is not exposed on the end face 51. The internal electrode 12b is exposed but the internal electrode 12a is not exposed on the end face 52. That is, the internal electrodes 12a and 12b are connected to the mutually different end faces 51 and 52, respectively.

[0023] 2 and 4, the capacitive region 60 is a central portion 62 in the X and Y directions of the element body 10 when viewed from the Z direction, where the internal electrodes 12a and 12b overlap. The end margin regions 64 are end portions of the element body 10 adjacent to both sides of the central portion 62 in the X direction when viewed from the Z direction, and are regions that include only one of the internal electrodes 12a or 12b.

[0024] For example, one end margin region 64 includes the internal electrode (first internal electrode) 12a but does not include the internal electrode (second internal electrode) 12b. The other end margin region 64 includes the internal electrode (first internal electrode) 12b but does not include the internal electrode (second internal electrode) 12a. The two end margin regions 64 each include an extension region where the internal electrode 12a is extended to the end face 51, and an extension region where the internal electrode 12b is extended to the end face 52.

[0025] In the Z direction, the uppermost internal electrode 12a and the lowermost internal electrode 12b do not have the first portion 13a but only have the second portion 13b. In the other internal electrodes 12a and 12b, the region within the end margin region 64 is the second portion 13b, the region within the end portion 63 on the end margin region 64 side within the capacitance region 60 is the second portion 13b, and the region within the central portion 61x sandwiched between the two end portions 63 in the X direction is the first portion 13a.

[0026] 3, the side margin region 66 is an end portion of the element body 10 in the Y direction, where the internal electrodes 12a and 12b are not provided. The side margin region 66 is formed by the side dielectric layers 18a and 18b. In each of the internal electrodes 12a and 12b other than the uppermost internal electrode 12a and the lowermost internal electrode 12b in the Z direction, the region within the end portion 65 on the side margin region 66 side of the capacitive region 60 in the Y direction is the second portion 13b, and the region within the central portion 61y sandwiched between the end portions 65 in the Y direction is the first portion 13a.

[0027] As shown in FIGS. 2, 4 and 5, the portions of the internal electrodes 12a and 12b that exist within the end margin region 64 of the element body 10 are all second portions 13b.

[0028] As described above, the capacitance region 60 has the second portions 13b of the internal electrodes 12a and 12b at both ends in each of the X, Y, and Z directions, and the first portions 13a of the internal electrodes 12a and 12b at the center in each of the X, Y, and Z directions. In other words, the second portions 13b of the internal electrodes 12a and 12b are provided on the surface of the capacitance region 60, and the first portions 13a of the internal electrodes 12a and 12b are provided inside the capacitance region 60.

[0029] The external electrode 20a contacts the internal electrode 12a exposed from the element body 10 at the end face 51. The external electrode 20b contacts the internal electrode 12b exposed from the element body 10 at the end face 52. The external electrode 20a covers the end faces in the -X direction of the side faces 53 and 54, the bottom face 55, and the top face 56 in addition to the end face 51. The external electrode 20b contacts the internal electrode 12b at the end face 51. The external electrode 20b covers the end faces in the +X direction of the side faces 53 and 54, the bottom face 55, and the top face 56 in addition to the end face 52.

[0030] The size of the multilayer ceramic capacitor 100 is, for example, 0.25 mm in length (length in the X direction), 0.125 mm in width (width in the Y direction), and 0.125 mm in height (height in the Z direction), or 0.4 mm in length, 0.2 mm in width, and 0.2 mm in height, or 0.6 mm in length, 0.3 mm in width, and 0.3 mm in height, or 1.0 mm in length, 0.5 mm in width, and 0.5 mm in height, or 3.2 mm in length, 1.6 mm in width, and 1.6 mm in height, or 4.5 mm in length, 3.2 mm in width, and 2.5 mm in height, but is not limited to these sizes.

[0031] The side dielectric layers 18a and 18b have a thickness of, for example, 10 μm to 30 μm. The length of the end margin region 64 in the X direction is, for example, 10 μm to 50 μm.

[0032] The internal electrodes 12a and 12b are mainly composed of nickel (Ni) and have a thickness of, for example, 0.1 μm or more and 1 μm or less.

[0033] The dielectric layer 14 has a main phase made of a ceramic material having a perovskite structure represented by the general formula ABO3. 3-α For example, the ceramic material includes barium titanate (BaTiO3), calcium zirconate (CaZrO3), calcium titanate (CaTiO3), strontium titanate (SrTiO3), magnesium titanate (MgTiO3), and BaTiO3, which forms a perovskite structure. 1-x-y Ca x Sr y Ti 1-z Zr z At least one of the following can be selected and used: O3 (0≦x≦1, 0≦y≦1, 0≦z≦1). 1-x-y Ca x Sr y Ti 1-z Zr zO3 is barium strontium titanate, barium calcium titanate, barium zirconate, barium titanate zirconate, calcium titanate zirconate, barium calcium titanate zirconate, etc. For example, the dielectric layer 14 contains 90 at% or more of the main component ceramic. The thickness of the dielectric layer 14 is, for example, 0.3 μm or more and 2 μm or less.

[0034] An additive may be added to the dielectric layer 14. Examples of additives to the dielectric layer 14 include oxides of zirconium (Zr), hafnium (Hf), magnesium (Mg), manganese (Mn), molybdenum (Mo), vanadium (V), chromium (Cr), rare earth elements (yttrium (Y), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and ytterbium (Yb)), oxides containing cobalt (Co), nickel (Ni), lithium (Li), boron (B), sodium (Na), potassium (K), or silicon (Si), or glasses containing cobalt, nickel, lithium, boron, sodium, potassium, or silicon.

[0035] The composition of the main ceramic of the cover dielectric layers 16a, 16b and the side dielectric layers 18a and 18b may be the same as or different from the main ceramic of the dielectric layer 14.

[0036] Of the external electrodes 20a and 20b, at least the layer (base metal layer 22) in contact with the internal electrodes 12a and 12b is primarily composed of copper (Cu) and contains ceramics such as a glass component for densifying the external electrodes 20a and 20b and a co-material for controlling the sinterability of the external electrodes 20a and 20b. The glass component is an oxide of barium (Ba), trontium (Sr), calcium (Ca), zinc, aluminum, silicon, boron, or the like. The co-material is, for example, a ceramic component primarily composed of the same material as the primary component of the dielectric layer 14. A plating film primarily composed of a base metal such as nickel, copper, or tin may be formed on the surfaces of the external electrodes 20a and 20b. Furthermore, a conductive resin film such as an epoxy resin or a urethane resin may be formed on the surface of the plating film.

[0037] (Manufacturing method of multilayer ceramic capacitors) A method for manufacturing the multilayer ceramic capacitor 100 will now be described. Fig. 6 is a flowchart showing a method for manufacturing the multilayer ceramic capacitor according to the embodiment.

[0038] (Green sheet molding process) First, a green sheet 30 is formed (step S10). In step S10, a dielectric material is prepared by adding various additive compounds (such as sintering aids) to ceramic powder, for example. A binder such as polyvinyl butyral (PVB) resin, an organic solvent such as ethanol or toluene, and a plasticizer are added to the prepared dielectric material and wet-mixed to produce a slurry. The produced slurry is then applied to a substrate using, for example, a die coater method or a doctor blade method to form a green sheet 30. The substrate is, for example, a PET (polyethylene terephthalate) film. The green sheet 30 is then dried.

[0039] Similarly, green sheets 31 for the cover dielectric layers 16a and 16b and the side dielectric layers 18a and 18b are formed. Copper or a copper compound is added to the dielectric material for the green sheets 31. The copper compound is, for example, copper oxide (CuO or CuO2). This makes the copper concentration of the green sheets 31 higher than the copper concentration of the green sheets 30.

[0040] (Pattern formation process) Next, a metal pattern 32 and a dielectric pattern 33 are formed on the green sheet 30 or 31 (step S12). Fig. 7(a) is a plan view showing a method for manufacturing a multilayer ceramic capacitor according to an embodiment, and Fig. 7(b) is a cross-sectional view taken along line AA in Fig. 7(a). Cutting lines 36 in Fig. 7(a) and Fig. 7(b) are cutting lines along which the multilayer sheet 35 is cut in step S18.

[0041] In step S12, a metal paste containing nickel powder, an organic binder, and an organic solvent is first prepared. The metal paste may contain ceramic particles as a co-material without adding copper. As shown in Figures 7(a) and 7(b), the metal paste is printed on a green sheet 30 using, for example, gravure printing to form a metal pattern 32.

[0042] Next, a dielectric paste containing ceramic powder, copper powder or copper compound powder, organic binder, organic solvent, and plasticizer is prepared. The copper compound is, for example, copper oxide (CuO or CuO2). The dielectric paste is printed on the green sheet 30 using, for example, gravure printing to form a dielectric pattern 33. The dielectric pattern 33 is the inverse pattern of the metal pattern 32, and it is preferable that there is almost no gap between the dielectric pattern 33 and the metal pattern 32.

[0043] In this way, a laminate sheet 34 is formed in which a metal pattern 32 and a dielectric pattern 33 are formed on the green sheet 30. Similarly to the green sheet 31, a metal pattern 32 and a dielectric pattern 33 are also formed on the green sheet 31 for the cover dielectric layer 16a, thereby forming a laminate sheet 34a.

[0044] (Lamination process) Next, the green sheet 31 and the laminate sheet 34a are laminated (step S14). FIG. 8 is a cross-sectional view showing the manufacturing method of the multilayer ceramic capacitor according to the embodiment, corresponding to the cross section AA in FIG. 7(a). In step S14, a plurality of laminate sheets 34 are laminated on the laminate sheet 34a, and finally, the green sheet 31 for the cover dielectric layer 16b is laminated. This forms a laminate sheet 35 in which the laminate sheet 34a and the plurality of laminate sheets 34 are laminated. At this time, the metal patterns 32 are provided alternately so that the position in the X direction is shifted for each layer.

[0045] (Crimping process) Next, the laminated sheet 35 is pressure-bonded (step S16). In step S16, the laminated sheet 35 formed in step S14 is pressed to pressure-bond the plurality of laminated sheets 34a and 34 together. As the pressure-bonding means, for example, a hydrostatic press is used.

[0046] (cutting process) Next, the laminate sheet 35 is cut (step S18). In step S18, a cutting blade is used to cut the laminate sheet 35 in the lamination direction along predetermined cutting lines 36, thereby preparing a plurality of laminates 11. FIG. 9 is a cross-sectional view showing the method for manufacturing the multilayer ceramic capacitor according to the embodiment, and corresponds to the cross section taken along line BB in FIGS. 1 to 5. As shown in FIG. 9, in the laminate 11, the internal electrodes 12a and 12b are exposed from the side surfaces 53a and 54a.

[0047] (side green sheet attached) Next, a side green sheet is attached (step S20). In step S20, the side surface 53a of the laminate 11 is pressed against the green sheet 31 for the side dielectric layer 18a, thereby attaching the green sheet 31 to the side surface 53a. Similarly, the green sheet 31 is attached to the side surface 54a of the laminate 11. After step S22, the element body 10 may be polished by a technique such as barrel polishing. This rounds the corners of the element body 10.

[0048] (Firing process) Next, the laminate 11 with the green sheets 31 attached to the side surfaces 53a and 54a is fired (step S22). In step S22, the laminate 11 with the green sheets 31 attached is subjected to a binder removal process in a nitrogen gas atmosphere at 250°C to 500°C, and then fired in a reducing atmosphere at 1300°C to 1400°C. This sinters the particles in the laminate 11 and the green sheets 31. During the binder removal process, which is performed at a temperature lower than that of the firing process, copper in the green sheets 31 and the dielectric pattern 33 diffuses into the metal pattern 32. If the green sheet 31 and the dielectric pattern 33 contain copper as copper oxide, the copper oxide is reduced and diffuses into the internal electrodes 12a and 12b. Hydrogen gas may be added to the atmosphere during the binder removal process to reduce the copper oxide. This increases the molar ratio of copper in the second portion 13b in FIGS. 2 to 4. On the other hand, copper does not diffuse as much into first portion 13a as into second portion 13b, and the copper molar ratio in first portion 13a is smaller than that in second portion 13b. By the binder removal process, most of the copper in green sheet 31 and dielectric pattern 33 moves to second portion 13b.

[0049] During the binder removal process, copper diffuses mainly into the second portion 13b, and therefore during the firing process, the copper in the green sheet 31 and the dielectric pattern 33 reacts with the nickel near the surfaces of the internal electrodes 12a and 12b, preventing the internal electrodes 12a and 12b from expanding.

[0050] (External electrode formation process) Next, the external electrodes 20a and 20b are formed (step S24). Step S24 includes steps S24a to S24c. FIGS. 10(a) and 10(b) are cross-sectional views showing a method for manufacturing a multilayer ceramic capacitor according to an embodiment, and show a cross section similar to that shown in FIG. 2. In step S24a, a metal paste containing copper powder, an organic binder, and an organic solvent is prepared. The metal paste may contain ceramic particles as an additive. As shown in FIG. 10(a), the metal paste is applied to the entire end face 51 of the element body 10 and to the ends of the side faces 53, 54, bottom face 55, and top face 56 on the end face 51 side, for example, by dipping.

[0051] Next, in step S24b, the metal paste is baked in a nitrogen atmosphere at 750°C to 850°C, which is lower than the baking temperature in step S22. As a result, the metal paste is baked onto element body 10, forming base metal layer 22. At this time, copper diffuses from base metal layer 22 into element body 10, but this diffusion is suppressed because copper is already contained in second portions 13b of internal electrodes 12a and 12b.

[0052] 10(b), a plating process is performed to form a plating layer 24 on the base metal layer 22. The plating layer 24 is, for example, a layer mainly composed of copper, a layer mainly composed of nickel, and a layer mainly composed of tin, from the side of the base metal layer 22. The base metal layer 22 and the plating layer 24 form the external electrodes 20a and 20b.

[0053] (Comparative multilayer ceramic capacitor) Fig. 11 is a cross-sectional view of a comparative multilayer ceramic capacitor 110, which corresponds to the cross section taken along line AA in Fig. 12. Fig. 12 is a cross-sectional view of the comparative multilayer ceramic capacitor 110, which corresponds to the cross section taken along line BB in Fig. 11. The comparative multilayer ceramic capacitor 110 is manufactured in a different manner from the multilayer ceramic capacitor 100 of the embodiment in that copper is not added to the green sheet 31 and the dielectric pattern 33 in steps S10 and S12 of Fig. 6.

[0054] 13(a) to 14(b) are schematic diagrams showing the copper molar ratio in the internal electrodes. FIGS. 13(a) and 13(b) are diagrams showing the copper molar ratio in the internal electrode 12a in the element body 10 after step S22 and before step S24 of FIG. 6, and FIGS. 14(a) and 14(b) are diagrams showing the copper molar ratio in the internal electrode 12a in the element body 10 after step S24. FIGS. 13(a) and 14(a) show the copper molar ratio versus position in the X direction in the internal electrode 12a. Line 75 indicates the copper molar ratio in the internal electrode 12a between the arrows labeled "75" in FIG. 11 for comparison. Lines 75a and 75b indicate the copper molar ratio in the internal electrode 12a between the arrows labeled "75a" and "75b," respectively, in FIG. 2 for the embodiment.

[0055] 13(b) and 14(b) show the copper molar ratio with respect to the position in the Y direction in the internal electrode 12a. Line 76 shows the copper molar ratio in the internal electrode 12a between the arrows indicated by "76" in FIG. 12 for comparison. Lines 76a and 76b show the copper molar ratio in the internal electrode 12a between the arrows indicated by "76a" and "76b" in FIG. 5 for the embodiment, respectively.

[0056] In the comparative multilayer ceramic capacitor 110, copper is not added to the green sheet 31 and the dielectric pattern 33. Therefore, as shown by lines 75 and 76 in Figures 13(a) and 13(b), the internal electrode 12a does not substantially contain copper after the firing treatment in step S22.

[0057] Furthermore, in step S24 of baking the base metal layer 22, as indicated by lines 75 and 76 in Figures 14(a) and 14(b), copper in the metal paste that will become the base metal layer 22 diffuses into the internal electrode 12a and reacts with nickel (see arrow 70 in Figure 11). This increases the molar ratio of copper in the end margin region 64. At this time, the molar ratio of copper is greatest at the end face 51 of the end margin region 64, and the molar ratio of copper decreases as the position from the end face 51 to the center portion 62 in the X direction increases.

[0058] When the diffused copper reacts with the nickel of the internal electrode 12a in the end margin region 64, the internal electrode 12a expands, and stress is applied to the end margin region 64 in the direction of expansion, as indicated by arrows 72 in Figures 11 and 12. This causes cracks 74 to form in the corners of the element body 10, as shown in Figures 11 and 12.

[0059] 6, the green sheet 31 and the dielectric pattern 33 contain copper. Therefore, in the binder removal process in step S22, the copper in the green sheet 31 and the dielectric pattern 33 mainly diffuses into the second portions 13b of the internal electrodes 12a and 12b. This is the finding of the inventors, and for example, when copper oxide such as CuO2 and CuO is added to a green sheet 30 mainly composed of barium titanate and the binder removal process is performed, copper diffuses into the internal electrodes 12a and 12b.

[0060] For example, when the molar ratio of CuO2 to BaTiO3 in the green sheet 31 is 2 mol%, the molar ratio of copper to nickel in the internal electrodes 12a and 12b in contact with the green sheet 31 is 4 mol%, and the molar ratio of copper to nickel in the internal electrodes 12a and 12b not in contact with the green sheet 31 is 2 mol%. Also, when the molar ratio of CuO2 to BaTiO3 in the green sheet 31 is 5 mol%, the molar ratio of copper to nickel in the internal electrodes 12a and 12b in contact with the green sheet 31 is 9.1 mol%, and the molar ratio of copper to nickel in the internal electrodes 12a and 12b not in contact with the green sheet 31 is 4.7 mol%.

[0061] Before the firing step (step S22), the element body 10 contains almost no copper in the green sheet 31 of the capacitance region 60. Therefore, when the firing step is performed, almost no copper is diffused into the region of the central portion 61x of the capacitance region 60 in the X direction in the internal electrode 12a near the center in the Z direction.

[0062] 13(a), the internal electrodes 12a in the central portion 61x contain almost no copper. On the other hand, because the dielectric pattern 33 contains copper before the firing process, copper diffuses from the dielectric pattern 33 to the internal electrodes 12a in the end margin regions 64 during the firing process.

[0063] 13(a), the copper molar ratio of the internal electrode 12a in the end margin region 64 is higher than the copper molar ratio of the internal electrode 12a in the central portion 61x. Furthermore, during the firing process, copper diffuses from the dielectric pattern 33 to the internal electrode 12a in the end portion 63 of the central portion 62 where the capacitive region 60 is present. Therefore, as shown by the line 75a in FIG. 13(a), the copper molar ratio of the internal electrode 12a in the end portion 63 is higher than the copper molar ratio of the internal electrode 12a in the central portion 61x and is substantially the same as the copper molar ratio of the internal electrode 12a in the end margin region 64.

[0064] Before the firing step, the green sheets 31 that will become the cover dielectric layers 16a and 16b contain copper. Therefore, during the firing step, copper diffuses from the green sheets 31 that will become the cover dielectric layers 16a and 16b to the uppermost (or lowermost) internal electrode 12a (12b) in the Z direction. Therefore, as shown in FIG. 13(a), in the central portion 61x of the laminate 11 in the X direction, the copper molar ratio of the uppermost internal electrode 12a (line 75b) is greater than the copper molar ratio of the internal electrode 12a near the center (line 75a).

[0065] Furthermore, in the firing process, copper diffuses from the green sheet 31 and the dielectric pattern 33 into the uppermost internal electrode 12a in the Z direction in the end margin region 64. Therefore, as shown in Fig. 13(a), in the end margin region 64 and the end portion 63, the copper molar ratio of the uppermost internal electrode 12a (line 75b) is greater than the copper molar ratio of the internal electrode 12a near the center (line 75a).

[0066] Before the firing process, the green sheets 31 that will become the side dielectric layers 18a and 18b contain copper, so that during the firing process, copper diffuses from the green sheets 31 that will become the side dielectric layers 18a and 18b to the internal electrodes 12a and 12b in the Y-direction end portion 65 of the capacitance region 60.

[0067] 13(b), for the internal electrode 12a near the center in the Z direction, the copper molar ratio of the internal electrode 12a in the end portion 65 in the Y direction is greater than the copper molar ratio of the internal electrode 12a in the central portion 61y in the Y direction (line 76a). Also, as shown in FIG. 13(b), in the central portion 61y in the Y direction, the copper molar ratio of the uppermost internal electrode 12a in the Z direction (line 76b) is greater than the copper molar ratio of the internal electrode 12a near the center in the Z direction (line 76a). Also at the end portion 65 in the Y direction, the copper molar ratio of the uppermost internal electrode 12a (line 76b) is greater than the copper molar ratio of the internal electrode 12a near the center in the Z direction (line 76a).

[0068] In summary, the copper molar ratio after the sintering step increases in the following order from range 80 to range 83b. Range 80 (copper molar ratio: 2.0): In the internal electrodes 12a and 12b near the center in the Z direction, the first portion 13a present in the central portion 61x in the X direction Range 81a (copper molar ratio: 4.0): In the internal electrodes 12a and 12b near the center in the Z direction, the second portion 13b present in the end margin region 64 and in the center portion 61y in the Y direction Range 81b (copper molar ratio: 4.2): The second portion 13b of the internal electrodes 12a and 12b near the center in the Z direction, which is present in the end margin region 64 and the end portion 65 in the Y direction. Range 82 (copper molar ratio: 4.6): The second portion 13b present in the central portion 61x in the X direction of the uppermost or lowermost internal electrode 12a or 12b in the Z direction. Range 83a (copper molar ratio: 4.8): The second portion 13b of the uppermost or lowermost internal electrode 12a or 12b in the Z direction, which is present in the end margin region 64 and in the central portion 61y in the Y direction. Range 83b (copper molar ratio: 5.0): The second portion 13b of the uppermost or lowermost internal electrode 12a or 12b in the Z direction, which is present within the end margin region 64 and the end portion 65 in the X direction.

[0069] In step S24, when the base metal layer 22 is formed, the internal electrodes 12a and 12b in the end margin region 64 contain copper, so in the multilayer ceramic capacitor 100 of the embodiment, the molar ratio of copper between the base metal layer 22 and the internal electrodes 12a and 12b is higher than that of the comparative multilayer ceramic capacitor 110. Therefore, in step S24b of baking the base metal layer 22, diffusion of copper from the base metal layer 22 to the internal electrodes 12a and 12b is suppressed, and the reaction between copper and nickel is suppressed.

[0070] As can be seen by comparing the lines 75, 75a, and 75b in FIG. 14(a) with the lines 75, 75a, and 75b in FIG. 13(a), respectively, in the multilayer ceramic capacitors 100 and 110, copper in the base metal layer 22 diffuses into a region extending from the end face 51 to the position Xdf in the X-direction of the end margin region 64. Here, the increase in copper in the end margin region 64 in the multilayer ceramic capacitor 100 of the embodiment is smaller than that in the comparative multilayer ceramic capacitor 110. Therefore, in the embodiment, the reaction between copper and nickel is suppressed, the stress indicated by the arrows 72 in FIGS. 11 and 12 is suppressed, and the occurrence of cracks 74 is suppressed.

[0071] 13(a), before step S24, in the end margin region 64, the copper molar ratio of the uppermost internal electrode 12a in the Z direction is greater than the copper molar ratio of the internal electrode 12a near the center in the Z direction. Therefore, in the uppermost internal electrode 12a, the diffusion of copper from the base metal layer 22 is more suppressed than in the internal electrode 12a near the center, and the reaction between copper and nickel is more suppressed.

[0072] As can be seen by comparing the lines 75a and 75b in FIG. 14(a) with the lines 75a and 75b in FIG. 13(a), the increase in the molar ratio due to copper diffusion into the uppermost internal electrode 12a in the end margin region 64 is smaller than the increase in the molar ratio due to copper diffusion into the internal electrode 12a near the center. Furthermore, the copper diffusion is limited to the end margin region 64, and copper does not substantially diffuse into the central portion 62 where the capacitance region 60 is located. Furthermore, as shown by the lines 76, 76a, and 76b in FIG. 14(b), near the end face 51, the molar ratios of copper in the uppermost internal electrode 12a, the internal electrode 12a near the center, and the internal electrode 12a of the comparative multilayer ceramic capacitor are substantially equal. This is because the base metal layer 22 contains more copper, its main component, than the amount that diffuses into the internal electrodes 12a and 12b.

[0073] In summary, the copper molar ratio after the external electrodes are formed in step S24 increases in the following range of 85 to 89 in that order. Range 85 (copper molar ratio: 2.0): In the internal electrodes 12a and 12b near the center in the Z direction, the first portion 13a present in the central portion 61x in the X direction Range 86 (copper molar ratio: 4.0): In the internal electrodes 12a and 12b near the center in the Z direction, the second portion 13b present in the end portion 63 and the end margin region 64 on the end portion 63 side in the X direction Range 87 (copper molar ratio: 4.6): The second portion 13b present in the central portion 61x in the X direction of the uppermost or lowermost internal electrode 12a or 12b in the Z direction Range 88 (copper molar ratio: 4.8): In the uppermost or lowermost internal electrodes 12a and 12b in the Z direction, the second portion 13b present in the end margin region 64 within the end 63 and on the end 63 side in the X direction Range 89 (copper molar ratio: 22): In the internal electrodes 12a and 12b, the second portion 13b present in the end margin region 64 near the end surface 51

[0074] As described above, in the multilayer ceramic capacitor 100 of the embodiment, copper is less likely to diffuse from the base metal layer 22 (metal paste) to the areas 86 and 88 of the internal electrodes 12a in the end margin region 64 than in the comparative multilayer ceramic capacitor 110, which suppresses the reaction between copper and nickel and the expansion of the internal electrodes 12a and 12b. This further suppresses the occurrence of cracks 74 as shown in FIGS. 11 and 12 .

[0075] According to the embodiment, before step S24, as shown in FIG. 13(a), the copper molar ratio in the range 81a is greater than the copper molar ratio in the range 80. As a result, after step S24b in which the metal paste is baked, as shown in FIG. 14(a), the increase in the copper molar ratio in the end margin region 64 due to copper diffused from the metal paste (lines 75a and 75b) can be reduced compared to the increase in the copper molar ratio in the comparative multilayer ceramic capacitor 110 (line 75). In other words, according to the multilayer ceramic capacitor 100 of the embodiment, the amount of copper diffused from the base metal layer 22 into the internal electrodes 12a, 12b after firing can be reduced compared to the comparative multilayer ceramic capacitor 110. This makes it possible to suppress the reaction between copper and nickel and to suppress the generation of cracks, etc. Furthermore, if copper oxide remains in the cover dielectric layers 16a, 16b, the side dielectric layers 18a, 18b, and the end margin region 64, the density of each is improved, improving the strength and moisture resistance of the element body 10.

[0076] The molar ratio of copper in the green sheets 30, 31 and the dielectric pattern 33 is, for example, the molar ratio of copper to the main component metal element of the ceramic. When the main component of the ceramic is barium titanate, the main component metal element is titanium or barium. When there are multiple main component elements, the metal element that is easier to detect can be used as the standard.

[0077] In steps S10 and S12, the molar ratio of copper to the main component metal element of the ceramic in green sheet 31 and dielectric pattern 33 is preferably 0.1 mol % to 10 mol %. Thus, before external electrode formation step S24, the molar ratio of copper to nickel in range 81 is, for example, 0.1 mol % to 20 mol %, and the molar ratio of copper to nickel in range 80 is, for example, 0 mol % to 10 mol %. For example, if the main component of the ceramic in green sheet 31 and dielectric pattern 33 is barium titanate and CuO2 is added as a copper compound, the molar ratio of copper to titanium in green sheet 31 and dielectric pattern 33 is 1 mol % to 10 mol %. In this case, the molar ratio of copper to nickel in range 81 is, for example, 1 mol % to 10 mol %, and the molar ratio of copper to nickel in range 80 is 0 mol % to 5 mol %.

[0078] After step S24, the molar ratio of copper to nickel in the range 86 is greater than the molar ratio of copper to nickel in the range 85. The molar ratio of copper to nickel in the range 85 is defined as the molar ratio of copper to nickel in the central portion 61x of the capacitance region 60. The molar ratio of copper to nickel in the range 86 is, for example, 1 to 7, and the molar ratio of copper to nickel in the range 85 is, for example, 0.5 to 4.0. The molar ratio of copper to nickel in the range 86 is preferably, for example, 1.2 times or more, more preferably 1.5 times or more, and even more preferably 2 times or more, of the molar ratio of copper to nickel in the range 85. When copper is contained in nickel, the resistance increases. Because the molar ratio of copper in the range 85 within the internal electrodes 12a and 12b in the capacitance region 60 is small, the resistance of the internal electrodes 12a and 12b can be reduced, thereby improving the capacitor characteristics.

[0079] 13(a) is made larger than the molar ratio of copper in range 80, the molar ratio of copper in ranges 80 and 81 within metal pattern 32 may be set to a desired value when forming laminated sheet 34 in FIGS. 7(a) and 7(b). However, it is difficult to change the molar ratio of copper within the same metal pattern 32.

[0080] 7(a) to 8, in the prepared laminate sheet 35, the molar ratio of copper to the main metal element of the ceramic of the dielectric pattern 33 provided in the end margin region 64 so as to contact the internal electrodes 12a and 12b in the X direction is greater than the molar ratio of copper to the main metal element of the ceramic of the green sheet 30 overlapping the internal electrodes 12a and 12b in the Z direction. In step S22, the laminate sheet 35 is fired. This makes it possible to more easily increase the molar ratio of copper in the range 81a in FIG. 13(a) than in the range 80.

[0081] Furthermore, before step S24, as shown in FIG. 13(b), the molar ratio of copper to nickel in the range 83a is higher than the molar ratio of copper to nickel in the range 81a. The molar ratio of copper to nickel in the range 83a is, for example, 1.5 to 7.5. As a result, in the end margin region 64, the reaction between copper and nickel is suppressed in the second portions 13b of the uppermost or lowermost internal electrodes 12a and 12b compared to the second portions 13b of the internal electrodes 12a and 12b near the center, thereby suppressing expansion of the internal electrodes 12a and 12b. Therefore, the occurrence of cracks 74 can be further suppressed. The molar ratio of copper in the range 88 is preferably, for example, 1.2 times or more, more preferably 1.5 times or more, of the molar ratio of copper in the range 86.

[0082] To make the copper molar ratio in range 82 greater than that in range 80, copper may be added to the green sheet 31 that will become the cover dielectric layers 16a and 16b in FIGS. 7(a) and 7(b). When manufactured in this manner, as shown in FIG. 14(a), the copper to nickel molar ratio in range 87 of the outermost internal electrodes 12a and 12b in the Z direction is greater than the copper to nickel molar ratio in range 85 of the central internal electrodes 12a and 12b. The copper molar ratio in range 87 is, for example, 1.5 to 7.5. The copper molar ratio in range 89 is preferably at least twice, more preferably at least three times, and even more preferably at least four times that of range 85.

[0083] 13(b), before step S24, the molar ratio of copper to nickel in the region 81b is higher than the molar ratio of copper to nickel in the region 81a. To increase the molar ratio of copper in the region 81b compared to the molar ratio of copper in the region 81a, copper may be added to the green sheet 31 that will become the side dielectric layers 18a and 18b in step S10 of forming the green sheet 30. When manufactured in this manner, within the capacitance region 60, the molar ratio of copper to nickel in the second portion 13b, which is the end portion of the internal electrodes 12a and 12b in the Y direction, is higher than the molar ratio of copper to nickel in the first portion 13a, which is the center portion of the internal electrodes 12a and 12b in the Y direction. Therefore, increasing the molar ratio of copper in the internal electrodes 12a and 12b near the side margin region 66 reduces copper diffusion, thereby suppressing the occurrence of cracks due to the volume expansion described above. In particular, since the corners of the element body 10 are the starting points of cracks, the occurrence of cracks can be more effectively suppressed by suppressing the diffusion of copper into the corners.

[0084] In the embodiment, as shown in Fig. 13(a), the molar ratio of copper to nickel of the uppermost or lowermost internal electrodes 12a and 12b in the Z direction is made larger than the molar ratio of copper to nickel of the central internal electrodes 12a and 12b in the Z direction, but the molar ratio of copper to nickel of the uppermost or lowermost internal electrodes 12a and 12b may be the same as that of the central internal electrodes 12a and 12b. As shown in Fig. 13(b), the molar ratio of copper to nickel of the internal electrodes 12a and 12b in the end portion 65 is made larger than the molar ratio of copper to nickel of the internal electrodes 12a and 12b in the central portion 61y, but the molar ratio of copper to nickel may be substantially the same between the end portion 65 and the central portion 61y.

[0085] When the molar ratio of copper to nickel is the same in the end portion 65 and the central portion 61y, the side margin region 66 may be formed from the laminated sheet 35 without performing step S20 in FIG.

[0086] In step S12, the metal paste does not contain copper, but may contain copper.

[0087] In this embodiment, the molar ratio is measured using, for example, EDS (Energy Dispersive X-ray Spectroscopy) or WDS (Wavelength Dispersive Spectroscopy). The molar ratio of copper to nickel of the internal electrodes 12a and 12b in the end margin region 64 is the molar ratio of copper to nickel near the center of the end margin region 64 in the X direction. The molar ratio of copper to nickel of the internal electrodes 12a and 12b in the capacitance region 60 is the molar ratio of copper to nickel near the center of the capacitance region 60 in the X direction. When comparing the molar ratios of copper to nickel of the internal electrodes 12a and 12b in the end margin region 64 on the side of the end faces 51 and 52, the molar ratios are compared at locations in the end margin region that are 5 μm or less away from the end faces 51 and 52 in the X direction and at the same distance. When comparing the molar ratio of copper to nickel at the end 65 of the internal electrodes 12a and 12b in the Y direction, the molar ratios are compared at points that are 5 μm or less and the same distance from the end of the internal electrodes 12a and 12b in the Y direction.

[0088] When a certain component contains a certain element as its main component, it is sufficient that the element is contained in the component to an extent that the effect of the embodiment is achieved, and the concentration of the element in the component is, for example, 50 mol % or more, 80 mol % or more, or 90 mol % or more.

[0089] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0090] 10 Base 12a, 12b internal electrode 13a Part 1 13b Part 2 14 Dielectric layer 16a, 16b Cover dielectric layer 18a, 18b Side dielectric layers 20a, 20b external electrode 30, 31 Green Sheet 32 Metal Pattern 33 Dielectric Pattern 34, 34a, 35 Laminated sheets 51, 52 End face 53, 54 Side 55 Bottom side 56 Top 61x, 61y center 60 capacity area 63, 65 End 64 End Margin Area 66 Side margin area 80~89 range

Claims

1. an element body in which a plurality of internal electrodes mainly made of nickel and a plurality of dielectric layers mainly made of ceramic are alternately stacked in a first direction, the stacked internal electrodes having a pair of end faces that are alternately exposed and face each other in a second direction; a pair of external electrodes in contact with the plurality of internal electrodes exposed from the pair of end faces, respectively, and having layers in contact with the plurality of internal electrodes, the layers containing copper as a main component; Equipped with a multilayer ceramic electronic component in which the molar ratio of copper to nickel in the first internal electrodes in an end margin region, which is an end portion of the element body in the second direction as viewed from the first direction and which includes a first internal electrode of the plurality of internal electrodes exposed on one of the pair of end faces but not a second internal electrode exposed on the other of the pair of end faces, is greater than the molar ratio of copper to nickel in the first internal electrodes in a capacity region, which is a central portion of the element body in the second direction as viewed from the first direction and in which the first internal electrode and the second internal electrode overlap each other.

2. 2. The multilayer ceramic electronic component according to claim 1, wherein, in the capacitance region, a molar ratio of copper to nickel of an internal electrode located outermost in the first direction among the plurality of internal electrodes is greater than a molar ratio of copper to nickel of an internal electrode located at a center in the first direction.

3. 3. The multilayer ceramic electronic component according to claim 1, wherein, within the capacitance region, a molar ratio of copper to nickel at ends of the internal electrodes in a third direction substantially perpendicular to the first direction and the second direction is greater than a molar ratio of copper to nickel at central portions of the internal electrodes in the third direction.

4. preparing an element body in which a plurality of internal electrodes mainly composed of nickel and a plurality of dielectric layers mainly composed of ceramic are alternately stacked in a first direction, the stacked internal electrodes having a pair of end faces that are alternately exposed and facing each other in a second direction, wherein a molar ratio of copper to nickel in the first internal electrodes in an end margin region that is an end portion of the element body in the second direction as viewed from the first direction and that includes a first internal electrode of the plurality of internal electrodes exposed at one of the pair of end faces and does not include a second internal electrode exposed at the other of the pair of end faces is greater than a molar ratio of copper to nickel in the first internal electrodes in a capacity region that is a central portion of the element body in the second direction as viewed from the first direction and where the first internal electrodes and the second internal electrodes overlap each other; forming a pair of external electrodes that are in contact with the plurality of internal electrodes exposed from the pair of end faces, respectively, and whose layers in contact with the plurality of internal electrodes are mainly composed of copper; A method for manufacturing a multilayer ceramic electronic component comprising:

5. The step of forming the pair of external electrodes includes: applying a metal paste to the plurality of internal electrodes exposed from the pair of end faces so as to contact the same; baking the applied metal paste; The method for producing a multilayer ceramic electronic component according to claim 4, comprising:

6. The step of preparing the element body includes: preparing a laminated sheet in which a molar ratio of copper to a main component metal element of ceramic of a dielectric pattern provided in the end margin region so as to be in contact with the second internal electrode in the second direction is larger than a molar ratio of copper to a main component metal element of ceramic of green sheets overlapped on the first internal electrode and the second internal electrode in the first direction; firing the laminated sheet; The method for producing a multilayer ceramic electronic component according to claim 4 or 5, comprising:

7. Before the step of forming the external electrodes, 6. The method for manufacturing a multilayer ceramic electronic component according to claim 4, wherein, in the capacitance region, a molar ratio of copper to nickel of an internal electrode located outermost in the first direction among the plurality of internal electrodes is greater than a molar ratio of copper to nickel of an internal electrode located at a center in the first direction.

8. Before the step of forming the external electrodes, 6. The method for manufacturing a multilayer ceramic electronic component according to claim 4, wherein, within the capacitance region, a molar ratio of copper to nickel at ends of the internal electrodes in a third direction substantially perpendicular to the first direction and the second direction is greater than a molar ratio of copper to nickel at central portions of the internal electrodes in the third direction.

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