Multilayer ceramic capacitor and circuit board

Abstract

To provide a multilayer ceramic capacitor in which bonding strength between a base conductor and a plating conductor is improved in a terminal electrode, and to provide a circuit board mounted with the same.SOLUTION: The multilayer ceramic capacitor includes a plurality of terminal electrodes connected to the internal electrodes, and the terminal electrodes are disposed on a mounting surface 11 facing a circuit board when mounted on the circuit board. The terminal electrode has a base conductor 41 in contact with the element body and a plating conductor covering the base conductor, and the base conductor has an edge having a wave-like undulation when viewed from a direction perpendicular to the element body surface.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a multilayer ceramic capacitor and a circuit board. [Background technology]

[0002] A wide variety of ceramic electronic components are used in high-frequency communication systems, such as mobile phones. These ceramic electronic components are required to be smaller and thinner, and efforts are being made to make them smaller and thinner in multilayer ceramic capacitors as well.

[0003] Multilayer ceramic capacitors are mounted on a circuit board via terminal electrodes (sometimes called external terminals or external electrodes) arranged on the surface of the element body. The terminal electrodes may include an underlying conductor (sometimes called an underlying electrode layer) formed on the element body and a plated conductor (sometimes called a plated layer) covering the underlying conductor (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2024-57048 [Patent Document 2] Japanese Patent Application Publication No. 2024-8171 Summary of the Invention [Problem to be solved by the invention]

[0005] As multilayer ceramic capacitors become smaller and thinner, the contact area between the element body and terminal electrode, and the contact area between the base conductor and plated conductor within the terminal electrode, are both decreasing, making it an issue to ensure the bonding strength between each part. For example, when soldering a multilayer ceramic capacitor to a circuit board, it is necessary to prevent peeling between the base conductor and plated conductor due to the thermal shock applied to the terminal electrode.

[0006] The present invention has been made to solve the above problems, and an object of the present invention is to provide a multilayer ceramic capacitor in which the bonding strength between the base conductor and the plated conductor in the terminal electrode is improved, and a circuit board on which the multilayer ceramic capacitor is mounted. [Means for solving the problem]

[0007] The inventors conducted various studies to solve the above-mentioned problems and found that the above-mentioned object can be achieved by forming the base conductor constituting the terminal electrode of the multilayer ceramic capacitor in such a way that at least a portion of the edge thereof is wavy when viewed from a direction perpendicular to the surface on which it is arranged, and thus completed the present invention.

[0008] That is, a first aspect of the present invention for solving the above-mentioned problems is a multilayer ceramic capacitor comprising: a laminate in which ceramic layers and internal electrodes mainly composed of metal are alternately stacked; a rectangular parallelepiped element body having a pair of cover portions arranged at both ends of the laminate in the stacking direction and covering the surface of the laminate; and margin portions covering at least a portion of the ends of the ceramic layers and the internal electrodes in the laminate and connecting the pair of cover portions to each other; and a plurality of terminal electrodes arranged at least on a mounting surface, which is the surface that faces a circuit board when mounted on the circuit board, among the surfaces forming the surface of the element body, and electrically connected to the internal electrodes, wherein the terminal electrodes have an underlying conductor in contact with the element body and a plated conductor covering the underlying conductor, and the underlying conductor has a shape such that at least a portion of an edge thereof has a wavy undulation when viewed from a direction perpendicular to the surface of the element body with which it contacts.

[0009] A second aspect of the present invention for solving the above problem is a circuit board on which the multilayer ceramic capacitor according to the first aspect is mounted. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a multilayer ceramic capacitor in which the bonding strength between the base conductor and the plated conductor in the terminal electrode is improved, and a circuit board on which the multilayer ceramic capacitor is mounted. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic view (perspective view) showing the structure of a multilayer ceramic capacitor according to a first embodiment of the present invention. [Figure 2] 2 is a cross-sectional view taken along line AA (LT cross-sectional view) in FIG. 1. [Figure 3] 1 is a schematic diagram (LW top view) showing the shape of an underlying conductor in a terminal electrode in the multilayer ceramic capacitor according to the first embodiment of the present invention. [Figure 4] 1 is a schematic diagram (LW top view) showing a preferred shape of a base electrode in the multilayer ceramic capacitor according to the first embodiment of the present invention. [Figure 5] FIG. 10 is a schematic diagram showing an SEM image that appears when determining whether the edge of the underlying conductor has wavy undulations. [Figure 6] FIG. 6 is a schematic diagram illustrating a method for calculating the protrusion dimension Ry0 of the boundary line between the underlying conductor and the plated conductor from the SEM image of FIG. 5. [Figure 7] FIG. 4 is a schematic view (LT cross-sectional view) showing the structure of a multilayer ceramic capacitor according to a second embodiment of the present invention. [Figure 8] 10 is a schematic diagram (LW top view) showing the shape of an underlying conductor in a terminal electrode in a multilayer ceramic capacitor according to a second embodiment of the present invention. FIG. [Figure 9] FIG. 10 is a schematic view (perspective view) showing the structure of a multilayer ceramic capacitor according to a third embodiment of the present invention. [Figure 10] 10 is a schematic diagram (LW top view) showing the shape of an underlying conductor in a terminal electrode in a multilayer ceramic capacitor according to a third embodiment of the present invention. FIG. [Figure 11] 13 is a schematic diagram (LW top view) showing the shape of an underlying conductor in a terminal electrode in a multilayer ceramic capacitor according to a first modified example of the third embodiment of the present invention. FIG. [Figure 12] 13 is a schematic diagram (LW top view) showing the shape of an underlying conductor in a terminal electrode in a multilayer ceramic capacitor according to a second modified example of the third embodiment of the present invention. FIG. [Figure 13] 13 is a schematic diagram (LW top view) showing the shape of an underlying conductor in a terminal electrode in a multilayer ceramic capacitor according to a third modified example of the third embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] The configuration and effects of the present invention will be described below, along with the technical concept, with reference to the drawings. However, the mechanism of action includes assumptions, and the correctness of such assumptions does not limit the present invention.

[0013] [Multilayer ceramic capacitors] First Embodiment An embodiment of a multilayer ceramic capacitor according to a first aspect of the present invention is shown in FIGS. 1 to 3 as a first embodiment. The multilayer ceramic capacitor 100 according to the first embodiment has a rectangular parallelepiped shape and includes a pair of faces perpendicular to each of three mutually orthogonal axes, i.e., the L axis, which is the length direction, the W axis, which is the width direction, and the T axis, which is the height direction. The rectangular parallelepiped is not limited to a mathematically defined rectangular parallelepiped, and may have any shape that is recognized as a rectangular parallelepiped when observed as a whole. Therefore, a rectangular parallelepiped in the present disclosure also includes a capacitor with slightly rounded edges or corners, a capacitor with slightly curved edges, and a capacitor with curved faces with a small curvature. The length (L), width (W), and height (T) dimensions of the ceramic capacitor 100 can each independently take any value.

[0014] The dimensions of the multilayer ceramic capacitor 100 are, for example, an L-direction dimension of 200 μm to 2000 μm, a W-direction dimension of 100 μm to 2000 μm, and a T-direction dimension of 30 μm to 220 μm, with a value W / L (the ratio of the W-direction dimension to the L-direction dimension) of 0.3 to 1.0. It is preferable that the L-direction dimension be 400 μm to 1200 μm, the W-direction dimension be 400 μm to 1200 μm, and the T-direction dimension be 40 μm to 150 μm, with a value W / L (the ratio of the W-direction dimension to the L-direction dimension) of 0.4 to 1.0. It is more preferable that the T-direction dimension be 100 μm or less, as this is less subject to design constraints on the circuit board on which it is mounted.

[0015] 2, the multilayer ceramic capacitor 100 according to the first embodiment includes an element body 10 having a laminate 20 in which ceramic layers 21 and internal electrodes 22 mainly composed of metal are alternately stacked in the T direction, a pair of cover portions 31 disposed at both ends of the laminate 20 in the stacking direction and covering the surface of the laminate 20, and margin portions 32 covering at least a portion of the ends of the ceramic layers 21 and the internal electrodes 22 in the laminate 20 and connecting the pair of cover portions 31 to each other. The internal electrodes 22 include internal electrodes 22a of one polarity that are electrically connected to each other, and internal electrodes 22b of a polarity different from that of the internal electrodes 22a that are electrically connected to each other.

[0016] There is no particular limitation on the method for electrically connecting the internal electrodes 22a to each other and the internal electrodes 22b to each other. Fig. 2 shows a mode in which the internal electrodes are connected by via conductors 23 (23a, 23b) that are arranged inside the element body 10 so as to penetrate the ceramic layers 21 in the stacking direction of the laminate 20 and have at least one end reaching the surface of a cover portion 31, which will be described later. However, as in a second embodiment, which will be described later, the internal electrodes may be extended to the end faces of the element body and connected by external conductors. Note that although the multilayer ceramic capacitor 100 shown in Fig. 2 has two via conductors 23, the number of via conductors in the multilayer ceramic capacitor according to the first aspect of the present invention is not limited to this.

[0017] On the surface of the element body 10, a cover portion 31 is arranged on a surface perpendicular to the T direction of the laminate 20, and margin portions 32 are arranged on surfaces perpendicular to the W direction and the L direction of the laminate. When the internal electrodes are drawn out to the end faces of the element body as in the second embodiment described later, no margin portions are arranged on the end faces (drawing faces) from which the internal electrodes are drawn out.

[0018] The multilayer ceramic capacitor 100 according to the first embodiment includes a plurality of terminal electrodes 40 (40a, 40b) disposed at least on a mounting surface 11, which is the surface that faces the circuit board when mounted on the circuit board, among the surfaces that form the surface of the element body 10. The terminal electrodes 40 (40a, 40b) are electrically connected to internal electrodes 22 (22a, 22b). The method for electrically connecting the terminal electrodes 40 (40a, 40b) to the internal electrodes 22 (22a, 22b) is not particularly limited. FIG. 2 shows a mode in which the terminal electrodes 40 are connected via via conductors 23 (23a, 23b), but they may also be connected via external conductors, as in a second embodiment described later. Note that although the multilayer ceramic capacitor 100 shown in FIG. 2 includes two terminal electrodes 40, the number of terminal electrodes in the multilayer ceramic capacitor according to the first aspect of the present invention is not limited to this.

[0019] The terminal electrode 40 (40a, 40b) has an underlying conductor 41 in contact with the element body 10 and a plated conductor 42 covering the underlying conductor 41. As shown in FIG. 3, the shape of the underlying conductor 41 is such that at least a portion of its edge has wavy undulations when viewed from a direction perpendicular to the surface of the element body 10 with which the underlying conductor 41 is in contact. Note that in this specification, the shape of the underlying conductor when viewed from a direction perpendicular to the surface of the element body with which the underlying conductor is in contact may be simply referred to as the "planar shape (of the underlying conductor)."

[0020] The thickness of the element body 10, obtained by subtracting the thickness of the terminal electrodes 40 (40a, 40b) from the T-direction dimension of the multilayer ceramic capacitor 100 described above, is, for example, 20 μm to 200 μm, and preferably 30 μm to 180 μm.

[0021] Hereinafter, each component constituting the multilayer ceramic capacitor 100 according to the first embodiment will be described in detail.

[0022] (ceramic layer) The ceramic layer 21 is made of ceramic. The ceramic composition is not particularly limited as long as it forms a dense ceramic layer 21 by co-firing with the internal electrodes 22 described later, and may be appropriately selected depending on the properties required for the multilayer ceramic capacitor. Examples of ceramic compositions include those containing barium titanate (BaTiO3) as the main component, those containing strontium titanate (SrTiO3) as the main component, and those containing BaTiO3 having a perovskite structure. 1-x-y Ca x Sr y Ti 1-z Zr z Examples of such ceramics include those containing O3 as a main component. The ceramic may contain an additive element in addition to the main component. Examples of the additive element include at least one selected from Mo, Nb, Ta, W, Mg, Mn, V, Cr, rare earth elements (Y, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb), and Co, Ni, Li, B, Na, K, and Si. The additive element may be contained as a simple element or in the form of a compound such as an oxide, nitride, or carbide. The additive element may exist in a solid solution state in the main component, or may form a different phase from the elements constituting the main component or other additive elements.

[0023] (internal electrode) The internal electrodes 22 (22a, 22b) are primarily composed of a metal. The type of metal is not particularly limited, and nickel (Ni), copper (Cu), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), and alloys thereof can be used. Among these, nickel (Ni) is preferred as the primary element because of its high heat resistance, which allows the firing temperature to be increased when co-firing with the ceramic layer 21 to form a dense ceramic layer 21, and it is relatively inexpensive. Here, the term "primary element" as used herein refers to the element with the highest content expressed in atomic percentage (atomic %).

[0024] The internal electrodes 22 (22a, 22b) may contain, in addition to metal, ceramic particles having the same composition as the ceramic constituting the ceramic layer 21, or a glass component.

[0025] (Cover and margin) Both the cover portion 31 and the margin portion 32 have the function of protecting the ceramic layer 21 and the internal electrode 22. The material of the cover portion 31 and the margin portion 32 is not limited as long as it has high electrical insulation and low permeability to deterioration factors such as moisture. From the viewpoints of making shrinkage during firing when manufacturing the multilayer ceramic capacitor 100 uniform and alleviating internal stress within the multilayer ceramic capacitor 100, it is preferable that the main component of the cover portion 31 and the margin portion 32 be the same as the ceramic that forms the ceramic layer 21.

[0026] (Via conductor) Like the internal electrodes 22 (22a, 22b), the via conductors 23 (23a, 23b) are primarily composed of metal. Usable metals include those similar to those used for the internal electrodes 22 (22a, 22b). The composition of the via conductors 23 (23a, 23b) may be different from that of the internal electrodes 22 (22a, 22b), but it is preferable that the composition of the via conductors 23 (23a, 23b) be the same as that of the internal electrodes 22 (22a, 22b). By making the via conductors 23 (23a, 23b) and the internal electrodes 22 (22a, 22b) the same composition, the magnitude of shrinkage caused by firing during manufacturing of the multilayer ceramic capacitor 100 is uniform, thereby suppressing deformation. In addition, the resistivity of the conductive paths of the multilayer ceramic capacitor 100 is uniform, thereby suppressing localized heat generation during use.

[0027] The diameter of the via conductors 23 (23a, 23b) is not particularly limited, but in order to ensure the capacity of the multilayer ceramic capacitor 100 while reducing electrical resistance and suppressing heat generation when the circuit is driven, it is preferable to make it 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 50 μm or less.

[0028] (terminal electrode) As described above, the terminal electrodes 40 (40a, 40b) have a base conductor 41 that contacts the element body 10 and a plating conductor 42 formed on the surface of the base conductor 41. The terminal electrodes 40 (40a, 40b) having such a structure can improve the adhesive force to the element body 10 by the base conductor 41 and can improve the solder wettability during circuit board mounting by the plating conductor 42.

[0029] As an example of the material of the base conductor 41, Ni is exemplified. The thickness of the base conductor 41 can be 0.1 μm or more and 10 μm or less, and preferably 0.5 μm or more and 5 μm or less.

[0030] As described above, the base conductor 41 has at least a part of its edge with a wavy undulation in the planar shape. This increases the contact area between the base conductor 41 and the plating conductor 42 and improves the bonding strength between the two.

[0031] 2]The effect of improving the bonding strength with the plating conductor 42 due to the edge of the base conductor 41 having a wavy undulation becomes more prominent as the area of the terminal electrodes 40 (40a, 40b) viewed from the direction perpendicular to the surface of the element body 10 with which the base conductor 41 contacts becomes smaller. For this reason, in the terminal electrodes 40 (40a, 40b) where the electrical connection with the internal electrodes 22 (22a, 22b) is made via the via conductors 23 (23a, 23b), the bonding strength between the base conductor 41 and the plating conductor 42 is significantly improved.

[0032] It is preferable that the protruding dimension Ry of the wavy undulation of the edge of the base conductor 41 is larger than the protruding dimension Ry0 of the boundary line with the plating conductor 42 in the cross section perpendicular to the surface of the element body 10 (mounting surface 11 in the multilayer ceramic capacitor 100) with which the base conductor 41 contacts. When the base conductor 41 satisfies Ry0 < Ry, the effect of improving the bonding strength with the plating conductor 42 due to the edge having a wavy undulation becomes prominent.

[0033] The protruding dimension Ry of the wavy undulation on the edge of the base conductor 41 is preferably 1.0 μm or more and 40 μm or less. When Ry is 3.0 μm or more, the increase in the bonding strength due to the increase in the contact area with the plating conductor 42 becomes remarkable. From this point of view, Ry is more preferably 3.0 μm or more, and even more preferably 5.0 μm or more. On the other hand, when Ry is 40 μm or less, peeling from the base body 10 starting from the protruding portion is effectively suppressed. Also, when forming the plating conductor 42, the contact state with the plating solution in the concave portion becomes good, and it becomes possible to form a plating conductor 42 with high homogeneity. From this point of view, Ry is more preferably 35 μm or less, and even more preferably 30 μm or less. From the above, Ry is more preferably 3.0 μm or more and 35 μm or less, and even more preferably 5.0 μm or more and 30 μm or less.

[0034] When viewed from a direction perpendicular to the surface of the base body 10 with which the base conductor 41 is in contact, the base conductor 41 has a rectangular shape. Among the two pairs of opposite edges, when the protruding dimension of the wavy undulation on one side is Ry1 and the protruding dimension of the wavy undulation on the other side is Ry2, it is preferable to satisfy 1.0 μm ≤ (Ry2 - Ry1) ≤ 35 μm (where Ry1 < Ry2). An example of the shape of such a base electrode 41 is shown in FIG. 4. In the rectangular base conductor 41, since (Ry2 - Ry1), which is the difference in the protruding dimensions between adjacent edges, is within the above range, it is possible to suppress variations in the conductivity of the terminal electrodes 40 (40a, 40b) and the bonding strength between the base conductor 41 and the plating conductor 42 among a plurality of multilayer ceramic capacitors 100. This is presumably because the edge with a large protruding undulation can increase the contact area with the plating conductor 42, and the decrease in conductivity and bonding strength due to the absence of plating formation in the concave portion at this edge can be suppressed by the edge with a small protruding undulation.

[0035] Here, the determination of whether the edge of the base conductor 41 has wavy undulations and the calculation of the edge protrusion dimension Ry and the protrusion dimension Ry0 of the boundary line with the plated conductor 42 are performed in the following manner: First, in the multilayer ceramic capacitor 100, a surface that is perpendicular to the surface on which the terminal electrode 40 (40a, 40b) to be determined is arranged and that is closest to the edge of interest of the terminal electrode 40 (40a, 40b) is provisionally determined as an observation surface. Next, when there is another terminal electrode 40 (40a, 40b) between the provisionally determined observation surface and the terminal electrode 40 (40a, 40b) to be determined, when the terminal electrode 40 (40a, 40b) to be determined is distant from the provisionally determined observation surface (the distance from the observation surface is approximately 100 μm or more), or when an extension line of a target edge of the terminal electrode 40 (40a, 40b) to be determined intersects with the provisionally determined observation surface, the actual observation surface is a cut surface obtained by cutting the vicinity of the target edge of the terminal electrode 40 (40a, 40b) to be determined along a plane parallel to the cut surface using a fine cutter or dicing saw, or a polished surface exposed by mechanically polishing the cut surface or the provisionally determined observation surface. On the other hand, when none of the above cases apply, the provisionally determined observation surface is the actual observation surface. Next, the multilayer ceramic capacitor 100, whose actual observation surface (hereinafter simply referred to as the "observation surface") has been determined, is placed in the chamber of a scanning electron microscope (SEM) combined with a focused ion beam (FIB) processing device, and observed from the observation surface side, with the focus set on the terminal electrodes 40 (40a, 40b) to be evaluated. Next, an ion beam is irradiated from the FIB device onto the terminal electrodes 40 (40a, 40b) to be evaluated, removing the terminal electrodes 40 (40a, 40b) to a certain depth from the surface, and the newly exposed surface is repeatedly observed with the SEM. Then, when the base conductor 41, which is recognized as an area with a different contrast from the plated conductor 42 as shown in FIG. 5(a) in the SEM image, is intermittently observed at the contact point with the element body 10, the multilayer ceramic capacitor 100 is removed from the SEM chamber. Next, for the removed multilayer ceramic capacitor 100, the dimension Rp of the terminal electrodes 40 (40a, 40b) to be evaluated in the direction perpendicular to the observation surface is measured.The measurement is performed by observing, with a microscope, the surface of the multilayer ceramic capacitor 100 on which the terminal electrodes 40 (40a, 40b) to be evaluated are arranged. Next, the multilayer ceramic capacitor 100 after the Rp measurement is placed again in the SEM chamber, and the terminal electrodes 40 (40a, 40b) to be evaluated are focused from the observation surface side. Then, the terminal electrodes are scraped off again using the FIB device, and the exposed surface is observed with the SEM, repeatedly. Then, as a result of the repetition, the underlying conductor 41, which was previously observed intermittently, appears continuously at the contact portion with the element body 10, as shown in Figure 5(b), and it is determined that the edge of the underlying conductor 41 has a wavy undulation. Next, in an SEM image in which the base electrode 41 appears continuously at the contact portion with the element body 10, as shown in FIG. 6, a line segment L defining the boundary between the element body 10 and the base conductor 41 is drawn. Among the line segments parallel to line segment L and tangent to the boundary between the base conductor 41 and the plated conductor 42, a line segment Lv that is the shortest from line segment L is drawn. Among the line segments parallel to line segment L and tangent to the boundary between the base conductor 41 and the plated conductor 42, a line segment Lp that is the longest from line segment L is drawn. Next, the distance between line segments Lv and Lp is measured in the SEM image. The measured value is divided by the magnification of the SEM image to obtain the protrusion dimension Ry0 of the boundary between the base conductor 41 and the plated conductor 42. Next, the multilayer ceramic capacitor 100 is removed from the SEM chamber, and the dimension Rv of the terminal electrode 40 (40a, 40b) to be evaluated in the direction perpendicular to the observation surface is measured. This measurement is performed in the same manner as for Rp. Next, the difference between Rp and Rv (Rp-Rv) is calculated, and the obtained value is set as the protruding dimension Ry of the edge portion.

[0036] When calculating Ry1 and Ry2 for a rectangular base conductor 41, the multilayer ceramic capacitor 100 is observed from a direction perpendicular to the surface on which the terminal electrodes 40 (40a, 40b) are arranged, and after confirming that the terminal electrodes 40 (40a, 40b) are rectangular, the above-mentioned Ry calculation procedure is performed on two observation surfaces that are perpendicular to each other.

[0037] The plated conductor 42 covering the underlying conductor 41 may be formed of a single layer or multiple layers. When the plated conductor 42 is formed of multiple layers, the number of layers is preferably two to four. An example of the material and structure of the plated conductor 42 is one formed of Cu, Ni, and Sn in this order. The thickness of the plated conductor 42 can be 1 μm to 20 μm, and preferably 3 μm to 10 μm.

[0038] The area of ​​the terminal electrodes 40 (40a, 40b), i.e., the area of ​​the terminal electrodes 40 (40a, 40b) observed when the multilayer ceramic capacitor 100 is viewed from a direction perpendicular to the mounting surface 11, is not particularly limited, as long as it is large enough to facilitate mounting on a circuit board and small enough to prevent short-circuiting between electrodes having opposite polarities. Preferably, the ratio of the total area of ​​the terminal electrodes 40 to the area of ​​the mounting surface 11 is 0.2 to 0.9, and more preferably, the ratio is 0.3 to 0.8.

[0039] <Second embodiment> In another embodiment (second embodiment) of the multilayer ceramic capacitor according to the first aspect of the present invention, the internal electrodes are electrically connected to each other by external conductors. An example of a multilayer ceramic capacitor 200 according to the second embodiment is shown in FIGS. 7 and 8. In the multilayer ceramic capacitor 200, the internal electrodes 22 (22a, 22b) extended to the lead-out surface 13 of the element body 10 are electrically connected to each other by external conductors 50 (50a, 50b), and the external conductors 50 (50a, 50b) are electrically connected to terminal electrodes 40 (40a, 40b) arranged on the mounting surface 11. Note that FIG. 7 shows an example in which the external conductors 50 (50a, 50b) are formed on a pair of opposing lead-out surfaces 13 and extend around to the opposing surface 12. However, the external conductors may be formed on only one lead-out surface, or may be formed on the lead-out surface 13 without extending around to the opposing surface.

[0040] <Third embodiment> In another embodiment (third embodiment) of the multilayer ceramic capacitor according to the first aspect of the present invention, the number of terminal electrodes arranged on the mounting surface is four or more. An example of a multilayer ceramic capacitor 300 according to the third embodiment is shown in FIGS. 9 and 10. Note that although FIGS. 9 and 10 show an example in which the number of terminal electrodes 40 arranged on the mounting surface 11 is four, the number of terminal electrodes arranged on the mounting surface is not limited to this. The multilayer ceramic capacitor 300 has the advantage of being able to suppress the amount of current flowing through the via conductors 23 (23a, 23b) electrically connected to the respective terminal electrodes 40 (40a, 40b), thereby reducing resistance heat generation. In addition, when the polarities of the terminal electrodes 40 (40a, 40b) closest to each other on the mounting surface 11 are different, the directions of the currents flowing through the via conductors 23 (23a, 23b) electrically connected to each terminal electrode 40 (40a, 40b) are opposite to each other in the closest via conductors 23 (23a, 23b), which results in the magnetic fields generated by the currents canceling each other out, thereby reducing the equivalent series inductance (ESL). The aforementioned ESL reduction effect is remarkable when the multilayer ceramic capacitor 300 has two pairs of opposing surfaces parallel to the stacking direction of the laminate, with the distance between one pair, i.e., the L-direction dimension, being L μm and the distance between the other pair, i.e., the W-direction dimension, being W μm (where L≧W), where W / L, the ratio of W to L, is 0.8 to 1, i.e., when the mounting surface 11 has a shape close to a square.

[0041] <Modification of the third embodiment> The planar shape of the base conductor in the multilayer ceramic capacitor 300 according to the third embodiment is not limited to that shown in FIG. 10, and may be, for example, a rectangular shape in which only two mutually perpendicular edges have wavy undulations (first modified example) as shown in FIG. 11, a circular shape as shown in FIG. 12 (second modified example), or a sector shape as shown in FIG. 13 (third modified example).

[0042] [Manufacturing method for multilayer ceramic electronic components] The multilayer ceramic capacitor according to the first aspect of the present invention can be manufactured by the procedure described below.

[0043] (A) Preparation of ceramic powder First, ceramic powder is prepared. Commercially available ceramic powders can be used as appropriate. When producing ceramic powder in-house, various raw material powders containing the constituent elements are mixed in a predetermined ratio and pre-fired (calcined). When mixing the various raw material powders in a predetermined ratio, various additives such as the above-mentioned additive elements and sintering aids may be further added, or these various additives may be further added to the powder after calcination.

[0044] (B) Preparation of raw sheets Next, the ceramic powder is mixed with a binder and a dispersion medium to prepare a slurry, and the slurry is formed into a sheet to obtain a green sheet.

[0045] The binder used should be one that can maintain the shape of the green sheet and volatilizes without leaving behind carbon or other residues during the binder removal process prior to firing. Examples of binders that can be used include polyvinyl alcohol, polyvinyl butyral, cellulose, urethane, and vinyl acetate. There are no particular restrictions on the amount of binder used, but since it will be removed in a later process, it is preferable to use as little as possible within the range that achieves the desired formability and shape retention, in order to reduce raw material costs.

[0046] The dispersion medium used is one that does not cause aggregation of the calcined powder and binder and can be easily removed by volatilization or the like after forming into a green sheet, as described below. Examples of the dispersion medium that can be used include water and alcohol-based solvents.

[0047] Components for adjusting the properties of the slurry, such as dispersants, plasticizers, and thickeners, may be added to the slurry.

[0048] The method for mixing the mixed powder with the binder and the dispersion medium is not particularly limited as long as the components are mixed uniformly while preventing the inclusion of impurities. One example is ball mill mixing.

[0049] The prepared slurry can be formed into a sheet to obtain a green sheet by a commonly used method such as a doctor blade method or a die coating method.

[0050] ((C) Formation of internal electrode pattern) Next, an internal electrode pattern containing metal is formed on the green sheet. The internal electrode pattern can be formed by printing or applying an internal electrode paste in a predetermined pattern, or by forming a metal film in a predetermined pattern by vapor deposition or sputtering. The internal electrode pattern is formed with a sufficient margin to ensure electrical insulation with the via conductor patterns that will be formed later and that will not come into contact with the via conductor patterns.

[0051] When forming an internal electrode pattern using an internal electrode paste, the internal electrode paste used is obtained by mixing metal particles and a vehicle in a triple roll mill. The internal electrode paste may contain glass frit and ceramic powder in addition to the above-mentioned components.

[0052] The type and amount of binder and solvent contained in the vehicle used are not limited, and may be selected appropriately taking into consideration the viscosity of the internal electrode paste, ease of handling, compatibility with the green sheet, and the like.

[0053] The internal electrode paste can be printed on the green sheet using, for example, a screen mask on which a predetermined internal electrode pattern is formed. When printing, a space may be left to become a margin when the multilayer ceramic capacitor is completed.

[0054] (D) Preparation of green laminate Next, a predetermined number of green sheets on which the internal electrode patterns have been formed are stacked and the green sheets are pressure-bonded together to obtain a green laminate. The stacking and pressure-bonding can be performed by a conventional method, such as pressing the stacked green sheets together in the stacking direction while heating them, and thermo-compression bonding by the action of a binder.

[0055] During lamination and compression bonding, a green sheet that will become a cover when the multilayer ceramic capacitor is completed may be added to the end portion in the lamination direction. In this case, the green sheet to be added may have the same composition as the green sheet on which the internal electrode pattern is printed, or a different composition. From the viewpoint of making the shrinkage rate during firing uniform, it is preferable that the composition of the green sheet to be added is the same as or similar to the green sheet on which the above-mentioned internal electrode precursor is arranged.

[0056] ((E) Formation of via conductor pattern) When manufacturing the multilayer ceramic capacitor according to the first embodiment, holes are then formed in the green laminate and filled with a conductive paste to form a via conductor pattern. Conventional methods such as drilling or lasers can be used to form the holes. Lasers are preferred because they can produce smooth surfaces. Conventional methods such as syringe injection and metal mask printing can be used to fill the holes with the conductive paste. Metal mask printing is preferred because it is superior in filling small holes. The components of the conductive paste can be the same as those of the internal electrode paste described above, and the amounts of each component can be determined taking into account the hole filling ability.

[0057] ((F) Formation of Undercoat Conductor Pattern) Next, a base conductor pattern is formed on at least one of the surfaces (mounting surface) perpendicular to the lamination direction of the green laminate. A green sheet, which will serve as a cover when the laminate is completed, may be crimped onto the opposite surface, where the base conductor pattern is not formed, so as to cover the via conductor pattern. The base conductor pattern can be formed by printing or applying a base conductor paste, or by forming a metal film by vapor deposition or sputtering. The base conductor pattern may be formed using a mask with a predetermined pattern having wavy undulations at the boundaries between openings and non-openings. Alternatively, the base conductor pattern may be formed by first forming a paste film or metal film on the entire mounting surface of the green laminate and then removing the portions other than the base conductor pattern. When the base conductor pattern is formed by removing the remaining portions, processing is performed to create wavy undulations on at least a portion of the edge. Removal of the portions other than the terminal electrode pattern can be performed using face milling, barrel polishing, or other methods. When using a terminal electrode paste to form the terminal electrode pattern, the components can be the same as those of the internal electrode paste described above. The blending amounts of each component can be determined to obtain a uniform pattern with a predetermined thickness.

[0058] (G) Preparation of pre-fired chips Next, the green laminate is divided into individual pieces to obtain pre-fired chips. For the division, a dicing saw, a laser cutter, or other commonly used means can be used. After dividing the green laminate into individual pieces to form surfaces on which the internal electrode precursors are exposed, the surfaces may be coated with a material for forming margins to obtain pre-fired chips.

[0059] (H) Removal of binder Next, the resulting pre-fired chips are heated to volatilize and remove the binder. The heating conditions can be set appropriately taking into account the volatilization temperature and content of the binder. For example, the chips are held in a nitrogen (N2) atmosphere at a temperature of 200 to 500°C for 5 to 20 hours.

[0060] (I) Firing of pre-fired chips Next, the pre-fired chip from which the binder has been removed is heated to a predetermined temperature and fired. When setting the firing conditions, it is preferable to consider the sinterability of the ceramic powder, as well as the heat resistance and oxidation resistance of the metals contained in the internal electrode pattern, via conductor pattern, and terminal electrode pattern. An example of firing conditions is holding the chip at a temperature of 1100°C to 1400°C for 10 minutes to 2 hours in a reducing atmosphere containing a mixture of nitrogen (N2), hydrogen (H2), and water vapor (H2O). After firing, a reoxidation treatment may be performed in which the chip is held at 600°C to 1000°C in a nitrogen (N2) gas atmosphere or a low-oxygen atmosphere.

[0061] (J) Formation of Underlayer on Outer Conductor When manufacturing the multilayer ceramic capacitor according to the second embodiment, the base conductor for the external conductor is formed simultaneously with the above (F) or subsequent to the above (I) without performing the above (E), or the base conductor for both the external conductor and the terminal electrode is formed subsequent to the above (I) without performing the above (E) and (F). Examples of methods for forming the external conductor and the terminal electrode include a method in which a conductive paste is applied by printing or dipping and then baked, and a method in which a metal film is formed by physical vapor deposition (PVD) such as evaporation.

[0062] ((K) Formation of plated conductor) Next, the sintered body having the base conductor disposed on its surface is subjected to a plating treatment to coat the surface of the base conductor with the plating conductor. The plating method is not particularly limited, and may be appropriately selected from commonly used electrolytic plating and electroless plating.

[0063] [Circuit board] A circuit board according to a second aspect of the present invention is equipped with the multilayer ceramic capacitor according to the first aspect. This circuit board is equipped with the multilayer ceramic capacitor with improved terminal electrode strength, and therefore has excellent durability and reliability.

[0064] This specification also discloses the following techniques.

[0065] (Appendix 1) a laminate in which ceramic layers and internal electrodes mainly composed of metal are alternately stacked; a pair of cover portions disposed at both ends of the laminate in the stacking direction and covering the surface of the laminate; and a margin portion that covers at least a portion of the ends of the ceramic layers and the ends of the internal electrodes in the laminate and connects the pair of cover portions to each other; have Rectangular element bodies, and A plurality of terminal electrodes are disposed at least on the mounting surface, which is the surface that faces the circuit board when mounted on the circuit board, among the surfaces that form the surface of the element body, and are electrically connected to the internal electrodes. Equipped with The terminal electrode has an underlying conductor in contact with the element body and a plated conductor covering the underlying conductor, and the underlying conductor has a shape in which at least a part of the edge thereof has a wavy undulation when viewed in a direction perpendicular to the surface of the element body with which it is in contact. Multilayer ceramic capacitor.

[0066] (Appendix 2) The multilayer ceramic capacitor according to (Supplementary Note 1), wherein at least one of the terminal electrodes is electrically connected to the internal electrode through a via conductor that passes through the laminate in the stacking direction.

[0067] (Appendix 3) The multilayer ceramic capacitor according to (Appendix 1) or (Appendix 2), wherein a protruding dimension Ry of the wavy undulations of the edge of the base conductor is larger than a protruding dimension Ry0 of a boundary line with the plated conductor in a cross section perpendicular to the surface of the element body with which the base conductor is in contact.

[0068] (Appendix 4) The multilayer ceramic capacitor according to (Appendix 3), wherein Ry is 1.0 μm or more and 40 μm or less.

[0069] (Appendix 5) The base conductor has a rectangular shape when viewed from a direction perpendicular to the surface of the element with which it is in contact. Among two pairs of mutually opposing edges, when the protruding dimension of the wavy undulation on one side is Ry1 and the protruding dimension of the wavy undulation on the other side is Ry2, a multilayer ceramic capacitor according to any one of (Appendix 1) to (Appendix 4) that satisfies 1.0 μm ≤ (Ry2 - Ry1) ≤ 35 μm (where Ry1 < Ry2).

[0070] (Appendix 6) A multilayer ceramic capacitor according to any one of (Appendix 1) to (Appendix 5), wherein the number of the plurality of terminal electrodes is 4 or more.

[0071] (Appendix 7) A multilayer ceramic capacitor according to (Appendix 6), wherein each terminal electrode has a different polarity from the other terminal electrode closest to it within the mounting surface.[[ID=!13]]

[0072] (Appendix 8) A circuit board on which a multilayer ceramic capacitor according to any one of (Appendix 1) to (Appendix 7) is mounted.

Industrial Applicability

[0073] According to the present invention, it is possible to provide a multilayer ceramic capacitor in which the bonding strength between the base conductor and the plating conductor in the terminal electrode is improved. Such a multilayer ceramic capacitor is useful in that it is less likely to be damaged by thermal shock during mounting on a circuit board, and thus a high mounting yield can be achieved. Further, the circuit board according to the present invention is useful in that it has excellent durability and reliability because it mounts a multilayer ceramic capacitor with improved terminal electrode strength.

Explanation of Signs

[0074] 100, 200, 300 Multilayer ceramic capacitor 10 Element 11 Mounting surface 12 Opposing surface 13 Lead-out surface 20 Laminate 21 Ceramic layer 22(22a, 22b) Internal electrode 23(23a, 23b) Via conductor 30 Protection Department 31 Cover 32 Margin 40(40a, 40b) terminal electrode 41 Undercoat conductor 42 Plated conductor 50(50a, 50b) Outer conductor

Claims

1. a laminate in which ceramic layers and internal electrodes mainly composed of metal are alternately stacked; a pair of cover portions disposed at both ends of the laminate in the stacking direction and covering the surface of the laminate; and a margin portion that covers at least a portion of the ends of the ceramic layers and the ends of the internal electrodes in the laminate and connects the pair of cover portions to each other; have Rectangular element bodies, and A plurality of terminal electrodes are disposed at least on the mounting surface, which is the surface that faces the circuit board when mounted on the circuit board, among the surfaces that form the surface of the element body, and are electrically connected to the internal electrodes. Equipped with The terminal electrode has an underlying conductor in contact with the element body and a plated conductor covering the underlying conductor, and the underlying conductor has a shape that has wavy undulations on at least a part of its edge when viewed from a direction perpendicular to the surface of the element body with which the underlying conductor is in contact. Multilayer ceramic capacitor.

2. 2. The multilayer ceramic capacitor according to claim 1, wherein at least one of the terminal electrodes is electrically connected to the internal electrode through a via conductor that passes through the laminate in the stacking direction.

3. 2. The multilayer ceramic capacitor according to claim 1, wherein a protrusion dimension Ry of the wavy undulations of the edge portion of the base conductor is larger than a protrusion dimension Ry0 of a boundary line with the plated conductor in a cross section perpendicular to a surface of the element body to which the base conductor contacts.

4. 4. The multilayer ceramic capacitor according to claim 3, wherein Ry is 1.0 μm or more and 40 μm or less.

5. 2. The multilayer ceramic capacitor according to claim 1, wherein the base conductor has a rectangular shape when viewed from a direction perpendicular to a surface of the element body with which it is in contact, and wherein, when a protruding dimension of the wavy undulations on one of two pairs of opposing edges is Ry1 and a protruding dimension of the wavy undulations on the other of two pairs of opposing edges is Ry2, the relationship satisfies 1.0 μm≦(Ry2−Ry1)≦35 μm (where Ry1<Ry2).

6. 2. The multilayer ceramic capacitor according to claim 1, wherein the number of said plurality of terminal electrodes is four or more.

7. 7. The multilayer ceramic capacitor according to claim 6, wherein each of said terminal electrodes has a polarity different from that of the other terminal electrode closest to said terminal electrode on said mounting surface.

8. A circuit board having the multilayer ceramic capacitor according to any one of claims 1 to 7 mounted thereon.

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