Multilayer ceramic electronic component and method for manufacturing the same

Abstract

To provide a multilayer ceramic electronic component which can improve the reliability and a method for manufacturing the same.SOLUTION: The multilayer ceramic electronic component has a laminate body in a substantially rectangular parallelepiped shape in which a plurality of first dielectric layers, a plurality of second dielectric layers with a smaller average thickness than those of the first dielectric layers, and a plurality of inner electrode layers are laminated. The first dielectric layers and the second dielectric layers are alternately laminated with the inner electrode layers in between and contain at least one type of rare-earth element. The concentration of the at least one type of rare-earth element to the ceramic as a main ingredient in the second dielectric layers is higher than the concentration of the at least one type of rare-earth element to the ceramic as a main ingredient in the first dielectric layers.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] In response to the demand for higher capacitance in multilayer ceramic electronic components such as multilayer ceramic capacitors, the dielectric layer between internal electrodes in the ceramic body has been thinned so that the number of layers increases (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when forming a thin dielectric layer, for example, it is not only difficult to peel the green sheet from a PET (Polyethylene Terephthalate) film of a base material without damage, but also when firing, the dielectric layer shrinks rapidly, increasing the difference in the amount of shrinkage between the side margin portion adjacent to the dielectric layer, and cracks are likely to occur in the ceramic body. Further, the thinner the dielectric layer, the more likely the insulation property is to deteriorate due to the movement of oxygen vacancies in the dielectric layer during firing, and there is a risk of deterioration in reliability.

[0005] Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a multilayer ceramic electronic component capable of improving reliability and a method for manufacturing the same.

Means for Solving the Problems

[0006] The multilayer ceramic electronic component of the present invention has a substantially rectangular parallelepiped-shaped laminate in which a plurality of first dielectric layers, a plurality of second dielectric layers having an average thickness smaller than that of the plurality of first dielectric layers, and a plurality of internal electrode layers are laminated. The first dielectric layer and the second dielectric layer are alternately laminated via the internal electrode layer, each containing at least one kind of rare earth element, and the concentration of the at least one kind of rare earth element with respect to the ceramic as the main component of the second dielectric layer is higher than the concentration of the at least one kind of rare earth element with respect to the ceramic as the main component of the first dielectric layer.

[0007] In the above multilayer ceramic electronic component, the concentration of the at least one kind of rare earth element with respect to the ceramic as the main component of the second dielectric layer may be 1.08 times or more the concentration of the at least one kind of rare earth element with respect to the ceramic as the main component of the first dielectric layer.

[0008] [[ID=X]] In the above multilayer ceramic electronic component, the concentration of the at least one kind of rare earth element with respect to the ceramic as the main component of the second dielectric layer may be 1.7 times or less the concentration of the at least one kind of rare earth element with respect to the ceramic as the main component of the first dielectric layer.

[0009] In the above multilayer ceramic electronic component, the first dielectric layer and the second dielectric layer each further contain magnesium and manganese, and the total concentration of the at least one kind of rare earth element, the magnesium, and the manganese with respect to the ceramic as the main component of the second dielectric layer may be 1.05 times or more the total concentration of the at least one kind of rare earth element, the magnesium, and the manganese with respect to the ceramic as the main component of the first dielectric layer.

[0010] In the above-described multilayer ceramic electronic component, the total concentration of the at least one rare earth element, the magnesium, and the manganese in the ceramic that is a main component of the second dielectric layer may be 1.5 times or less of the total concentration of the at least one rare earth element, the magnesium, and the manganese in the ceramic that is a main component of the first dielectric layer.

[0011] In the above-described multilayer ceramic electronic component, the average particle size of the ceramic particles contained in the first dielectric layer may be larger than the average particle size of the ceramic particles contained in the second dielectric layer.

[0012] In the above-described multilayer ceramic electronic component, the laminate may further include a plurality of third dielectric layers stacked on it, each of the third dielectric layers having an average thickness smaller than that of the second dielectric layers, the third dielectric layers being stacked between the first dielectric layer and the second dielectric layer via the internal electrode layers, each containing the at least one rare earth element, and the concentration of the at least one rare earth element in the ceramic that is a main component of the third dielectric layers being higher than the concentration of the at least one rare earth element in the ceramic that is a main component of the second dielectric layer.

[0013] The manufacturing method of the multilayer ceramic electronic component of the present invention includes a step of forming a first green sheet by applying a ceramic slurry added with at least one rare earth element onto a substrate, a step of forming a first internal electrode pattern on the first green sheet, a step of forming a second green sheet by applying the ceramic slurry onto the first green sheet and the first internal electrode pattern so that the average thickness becomes smaller than that of the first green sheet, a step of forming a second internal electrode pattern on the second green sheet, a step of peeling the first green sheet and the second green sheet from the substrate, a step of laminating and pressing a plurality of sets of the first green sheet and the second green sheet, a step of dividing the plurality of sets of the laminated and pressed first green sheet and second green sheet into a plurality of laminates along the lamination direction, and a step of firing the laminate. In the step of forming the second green sheet, the ceramic slurry is adjusted so that the concentration of the at least one rare earth element with respect to the ceramic as the main component of the second green sheet becomes higher than the concentration of the at least one rare earth element with respect to the ceramic as the main component of the first green sheet.

[0014] Another method for manufacturing a multilayer ceramic electronic component of the present invention includes a step of forming a first green sheet by applying a ceramic slurry containing at least one rare earth element onto a substrate, a step of forming a first internal electrode pattern on the first green sheet, a step of forming a second green sheet by applying the ceramic slurry onto the first green sheet and the first internal electrode pattern such that the average thickness is smaller than that of the first green sheet, a step of forming a second internal electrode pattern on the second green sheet, a step of forming a third green sheet by applying the ceramic slurry onto the second green sheet and the second internal electrode pattern such that the average thickness is smaller than that of the second green sheet, a step of forming a third internal electrode pattern on the third green sheet, a step of peeling the first green sheet, the second green sheet, and the third green sheet from the substrate, a step of laminating and pressing a plurality of sets of the first green sheet, the second green sheet, and the third green sheet, a step of dividing the laminated and pressed plurality of sets of the first green sheet, the second green sheet, and the third green sheet into a plurality of laminates along the lamination direction, and a step of firing the laminate. In the step of forming the second green sheet, the ceramic slurry is adjusted such that the concentration of the at least one rare earth element with respect to the ceramic as the main component of the second green sheet is higher than the concentration of the at least one rare earth element with respect to the ceramic as the main component of the first green sheet. In the step of forming the third green sheet, the ceramic slurry is adjusted such that the concentration of the at least one rare earth element with respect to the ceramic as the main component of the third green sheet is higher than the concentration of the at least one rare earth element with respect to the ceramic as the main component of the second green sheet.

Advantages of the Invention

[0015] According to the present invention, the reliability of the multilayer ceramic electronic component can be improved.

Brief Description of the Drawings

[0016]

Figure 1

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Figure 11

Mode for Carrying Out the Invention

[0017] [Embodiment] (Configuration of Multilayer Ceramic Capacitor) Figure 1 is a perspective view showing an example of the multilayer ceramic capacitor 1. Figure 2 is a cross-sectional view of the multilayer ceramic capacitor 1 taken along line A-A of Figure 1. Figure 3 is a cross-sectional view of the multilayer ceramic capacitor 1 taken along line B-B of Figure 2. Figure 4 is a cross-sectional view of the multilayer ceramic capacitor 1 taken along line C-C of Figure 2.

[0018] The multilayer ceramic capacitor 1 has a laminate 2 having a substantially rectangular parallelepiped shape and external electrodes 3a, 3b provided on a pair of opposing end faces 2A, 2B of the laminate 2. The multilayer ceramic capacitor 1 is an example of a multilayer ceramic electronic component. Other examples of multilayer ceramic electronic components include a multilayer ceramic varistor and a multilayer ceramic thermistor, and in this embodiment, the multilayer ceramic capacitor 1 is used as a representative example of these.

[0019] 1 to 4 show mutually orthogonal X, Y, and Z directions. The X direction is the length (L) direction of the multilayer ceramic capacitor 1 and coincides with the direction in which a pair of end faces 2A, 2B of the laminate 2 face each other. The Y direction is the width (W) direction of the multilayer ceramic capacitor 1 and coincides with the direction in which a pair of side faces 2E, 2F of the laminate 2 face each other. The Z direction is the height (T) direction of the multilayer ceramic capacitor 1 and coincides with the direction in which the upper face 2C and the lower face 2D of the laminate 2 face each other and the lamination direction of the multilayer ceramic capacitor 1. The width direction is an example of a direction approximately orthogonal to the lamination direction of the laminate 2.

[0020] The laminate 2 has an upper surface 2C, a lower surface 2D, a pair of end surfaces 2A and 2B, and a pair of side surfaces 2E and 2F. The upper surface 2C and the lower surface 2D are generally flat surfaces that face each other in the stacking direction, the pair of end surfaces 2A and 2B are generally flat surfaces that face each other in the length direction, and the pair of side surfaces 2E and 2F are generally flat surfaces that face each other in the width direction.

[0021] The laminate 2 has a laminated structure in which dielectric layers 22a, 22b containing a ceramic material that functions as a dielectric and internal electrode layers 23a, 23b are alternately laminated, and a pair of cover layers 20, 21 are laminated so as to sandwich the dielectric layers 22a, 22b and the internal electrode layers 23a, 23b from both sides in the lamination direction. In the laminate 2, the portion sandwiched between the pair of internal electrode layers 23a, 23b adjacent to each dielectric layer 22a, 22b contributes to the capacitance of the multilayer ceramic capacitor 1 and is sometimes called a "capacitive layer."

[0022] The cover layers 20 and 21 sandwich the capacitive layer from both sides in the stacking direction. Edge portions 200 and 210 having curved surfaces are formed on both ends of the cover layers 20 and 21 in the longitudinal direction, respectively.

[0023] The laminate 2 also has side margins 40, 41 that cover the side surfaces 2E, 2F. The side margins 40, 41 extend along the length direction and sandwich the laminated regions of the internal electrode layers 23a, 23b and the dielectric layers 22a, 22b, i.e., the capacitive layers, from both sides in the width direction. The side margins 40, 41 are mainly composed of the same ceramic material as the dielectric layers 22a, 22b.

[0024] The internal electrode layers 23a, 23b have a substantially rectangular shape when viewed from the front in the stacking direction, and face each other in the stacking direction with the dielectric layers 22a, 22b sandwiched between them. The internal electrode layers 23a, 23b are alternately arranged along the stacking direction. One end of the internal electrode layer 23a is extended to one end face 2A and connected to one external electrode 3a, and one end of the internal electrode layer 23b is extended to the other end face 2B and connected to the other external electrode 3b. The internal electrode layers 23a, 23b have substantially the same average thickness.

[0025] The internal electrode layers 23a, 23b are mainly composed of base metals such as Ni (nickel), Cu (copper), and Sn (tin). The internal electrode layers 23a, 23b may be made of precious metals such as Pt (platinum), Pd (palladium), Ag (silver), and Au (gold), or alloys containing these metals. The thickness of the internal electrode layers 23a, 23b is, for example, 0.05 to 0.6 μm or less.

[0026] The dielectric layers 22a and 22b have a main phase made of a ceramic material having a perovskite structure represented by the general formula ABO3. 3-αincluding (α represents a minute number). For example, as the ceramic material, BaTiO3 (barium titanate), CaZrO3 (calcium zirconate), CaTiO3 (calcium titanate), SrTiO3 (strontium titanate), MgTiO3 (magnesium titanate), Ba forming a perovskite structure 1-x-y Ca x Sr y Ti 1-z Zr z O3 (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1), etc., and at least one of them can be selected and used. Ba 1-x-y Ca x Sr y Ti 1-z Zr z O3 includes barium strontium titanate, barium calcium titanate, barium zirconate, barium zirconium titanate, calcium zirconium titanate, and barium calcium zirconium titanate, etc.

[0027] The dielectric layers 22a, 22b are alternately laminated via the internal electrode layers 23a, 23b. The dielectric layers 22a, 22b are each sandwiched by the internal electrode layers 23a, 23b from above and below in the lamination direction. Note that the dielectric layer 22a is an example of the first dielectric layer, and the dielectric layer 22b is an example of the second dielectric layer.

[0028] The average thicknesses Da, Db of the dielectric layers 22a, 22b are different. In this example, the average thickness Da of the dielectric layer 22a is larger than the average thickness Db of the dielectric layer 22b. Here, the average thicknesses Da, Db refer to the average value of the thickness along the lamination direction in the XY plane.

[0029] As described above, in the laminate 2, a dielectric layer 22a having a large average thickness Da and a dielectric layer 22b having a small average thickness Db are alternately laminated in the lamination direction. Therefore, when sintering the laminate 2 in the manufacture of the multilayer ceramic capacitor 1, a difference can be provided in the sinterability of each dielectric layer 22a, 22b. Specifically, due to the difference in the average thicknesses Da and Db, for example, the shrinkage amounts and shrinkage timings of the dielectric layers 22a, 22b during sintering are different, so that the difference in shrinkage amount between the side margin portions 40, 41 and the cover layers 20, 21 adjacent to the periphery of the laminated regions of the dielectric layers 22a, 22b and the internal electrode layers 23a, 23b and the laminate 2 is reduced.

[0030] Therefore, compared with the case where each average thickness Da, Db is the same, the stress due to the shrinkage of each dielectric layer 22a, 22b can be dispersed. Thereby, the generation of cracks in the laminate 2 is suppressed.

[0031] In order to suppress the generation of cracks, the average thickness Da of the dielectric layer 22a is preferably 1.05 to 2.0 times the average thickness Db of the dielectric layer 22b. More preferably, the average thickness Da of the dielectric layer 22a may be 1.1 to 1.3 times the average thickness Db of the dielectric layer 22b.

[0032] In order to suppress the generation of cracks, the average thickness Da of the dielectric layer 22a is preferably 0.4 to 0.8 μm, and the average thickness Db of the dielectric layer 22b is preferably 0.3 to 0.7 μm. More preferably, the average thickness Da of the dielectric layer 22a may be 0.4 to 0.6 μm, and the average thickness Db of the dielectric layer 22b may be 0.3 to 0.5 μm.

[0033] As an example, the measurement of the average thicknesses Da, Db of the dielectric layers 22a, 22b is performed by adjusting the magnification of a scanning electron microscope or a transmission electron microscope so that about 3 to 4 layers of the dielectric layers 22a, 22b are imaged in one image, and measuring the thicknesses at 10 equally spaced positions for each layer.

[0034] Further, the dielectric layers 22a and 22b and the cover layers 20 and 21 are obtained, for example, by firing raw material powders of a main component ceramic having a perovskite structure. Since the raw material powders are exposed to a reducing atmosphere during firing, oxygen defects (oxygen vacancies) are generated in the main component ceramic. Therefore, the dielectric layers 22a and 22b and the cover layers 20 and 21 contain at least one rare earth element that replaces the B site of the perovskite structure represented by ABO3 and functions as a donor element. Examples of the rare earth element that functions as a donor element include, but are not limited to, Mo, Nb, Ta, and W. By adding a donor element to the dielectric layers 22a and 22b, the amount of generation and movement of oxygen defects in the main component ceramic is suppressed, and its insulation properties are improved.

[0035] The concentration of the rare earth element with respect to the ceramic of the main component of the dielectric layer 22b is higher than the concentration of the rare earth element with respect to the ceramic of the main component of the dielectric layer 22a. For this reason, in the thin dielectric layer 22b, the amount of generation and movement of oxygen defects is suppressed more than in the thick dielectric layer 22a. Therefore, compared with the case where the concentrations of the rare earth elements in the dielectric layers 22a and 22b are the same, the insulation properties of the multilayer ceramic capacitor 1 can be appropriately improved according to the average thickness of the dielectric layers 22a and 22b.

[0036] As described above, according to the multilayer ceramic capacitor 1, the occurrence of cracks is suppressed and the insulation properties are improved, so the reliability is improved.

[0037] In order to improve the reliability of the multilayer ceramic capacitor 1, the concentration of the rare earth element with respect to the ceramic of the main component of the dielectric layer 22b is preferably 1.08 times or more the concentration of the rare earth element with respect to the ceramic of the main component of the dielectric layer 22a. More preferably, the concentration of the rare earth element with respect to the ceramic of the main component of the dielectric layer 22b may be 1.15 times or more the concentration of the rare earth element with respect to the ceramic of the main component of the dielectric layer 22a.

[0038] In order to increase the capacitance of the multilayer ceramic capacitor 1, the concentration of the rare earth element with respect to the ceramic that is the main component of the dielectric layer 22b is preferably 1.7 times or less the concentration of the rare earth element with respect to the ceramic that is the main component of the dielectric layer 22a. More preferably, the concentration of the rare earth element with respect to the ceramic that is the main component of the dielectric layer 22b may be 1.5 times or less the concentration of the rare earth element with respect to the ceramic that is the main component of the dielectric layer 22a.

[0039] For example, the concentration of the rare earth element with respect to the ceramic that is the main component of the dielectric layer 22a is 0.5 to 2.0 atm%, and the concentration of the rare earth element with respect to the ceramic that is the main component of the dielectric layer 22b is 0.7 to 2.2 atm%.

[0040] The dielectric layers 22a and 22b and the cover layers 20 and 21 may each further contain magnesium (Mg) and manganese (Mn). Thereby, the dielectric layers 22a and 22b and the cover layers 20 and 21 can improve the insulation property as compared with the case where they do not contain magnesium and manganese.

[0041] In order to improve the reliability of the multilayer ceramic capacitor 1, the total concentration of the rare earth element, magnesium, and manganese with respect to the ceramic that is the main component of the dielectric layer 22b is preferably 1.05 times or more the total concentration of the rare earth element, magnesium, and manganese with respect to the ceramic that is the main component of the dielectric layer 22a. More preferably, the total concentration of the rare earth element, magnesium, and manganese with respect to the ceramic that is the main component of the dielectric layer 22b is preferably 1.2 times or more the total concentration of the rare earth element, magnesium, and manganese with respect to the ceramic that is the main component of the dielectric layer 22a.

[0042] In order to increase the capacitance of the multilayer ceramic capacitor 1, it is preferable that the total concentration of rare earth elements, magnesium, and manganese with respect to the ceramic that is the main component of the dielectric layer 22b is 1.5 times or less the total concentration of rare earth elements, magnesium, and manganese with respect to the ceramic that is the main component of the dielectric layer 22a. More preferably, the total concentration of rare earth elements, magnesium, and manganese with respect to the ceramic that is the main component of the dielectric layer 22b is 1.3 times or less the total concentration of rare earth elements, magnesium, and manganese with respect to the ceramic that is the main component of the dielectric layer 22a.

[0043] For example, the concentration of magnesium with respect to the ceramic that is the main component of the dielectric layer 22a is 0 to 1.0 atm%, and the concentration of magnesium with respect to the ceramic that is the main component of the dielectric layer 22b is 0.05 to 1.1 atm%. For example, the concentration of manganese with respect to the ceramic that is the main component of the dielectric layer 22a is 0 to 1.0 atm%, and the concentration of manganese with respect to the ceramic that is the main component of the dielectric layer 22b is 0.05 to 1.1 atm%.

[0044] (Particle size of ceramic particles) Depending on the average thicknesses Da and Db of the dielectric layers 22a and 22b, the average particle sizes of the ceramic particles contained in the respective dielectric layers 22a and 22b may be different.

[0045] FIG. 5 is a cross-sectional view showing an example of the fine structure of the region P shown in FIG. 2. The dielectric layer 22a is formed of a large number of ceramic particles 220a, the dielectric layer 22b is formed of a large number of ceramic particles 220b, and the end margin portion 22m is formed of a large number of ceramic particles 220m.

[0046] The average particle size of the ceramic particles 220a is larger than the average particle size of the ceramic particles 220b. Thus, of the dielectric layers 22a and 22b, the dielectric layer 22a with the larger average thickness contains ceramic particles 220a with a larger average particle size, and the dielectric layer 22b with the smaller average thickness contains ceramic particles 220b with a smaller average particle size.

[0047] Therefore, the dielectric layers 22a, 22b are not only appropriately smoothed according to their average thickness, but also the size of the grain boundaries between the ceramic particles 220a, 220b is appropriately adjusted according to the average thickness, thereby suppressing the movement of oxygen vacancies, thereby improving the flatness and insulating properties of the dielectric layers 22a, 22b compared to when the average particle size of the ceramic particles 220a, 220b is not set as described above.

[0048] In order to improve both the reliability and capacitance of the multilayer ceramic capacitor 1, the average particle size of the ceramic particles 220a is preferably 1.15 to 2.0 times the average particle size of the ceramic particles 220b. More preferably, the average particle size of the ceramic particles 220a may be 1.4 to 1.65 times the average particle size of the ceramic particles 220b.

[0049] The ceramic particles 220a preferably have an average particle size of 80 to 350 nm and the ceramic particles 220b have an average particle size of 70 to 300 nm in order to improve both the reliability and capacitance of the multilayer ceramic capacitor 1. More preferably, the ceramic particles 220a may have an average particle size of 80 to 150 nm and the ceramic particles 220b may have an average particle size of 70 to 100 nm.

[0050] The average particle size of the ceramic particles 220m contained in the end margin portion 22m is 75 to 330 nm, which makes it possible to more effectively relieve stress and suppress the occurrence of cracks.

[0051] The average particle size of the ceramic particles 220a, 220b, and 220m is measured, for example, by adjusting the magnification of a scanning electron microscope or a transmission electron microscope so that approximately 80 to 150 crystal grains are captured in one image and measuring the Feret diameter of all the crystal grains in the image. Here, the Feret diameter is the diameter in the direction parallel to the stacking direction of the multilayer ceramic capacitor 1.

[0052] (Another embodiment of the multilayer ceramic capacitor) The above multilayer ceramic capacitor 1 has a laminate 2 in which two dielectric layers 22a and 22b with different average thicknesses are alternately laminated. However, as in the following example, it may have a laminate 2 in which three dielectric layers are repeatedly laminated.

[0053] FIG. 6 is a cross-sectional view of a multilayer ceramic capacitor 1a according to another embodiment taken along line A-A of FIG. 1. In FIG. 6, the components common to FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.

[0054] In the laminate 2, in addition to the above dielectric layers 22a and 22b, a dielectric layer 22c having an average thickness Dc different from those of the dielectric layers 22a and 22b is laminated. The average thickness Dc of the dielectric layer 22c is smaller than the average thicknesses Da and Db of the dielectric layers 22a and 22b.

[0055] In the laminate 2, the dielectric layers 22a to 22c are repeatedly laminated in the stacking direction via the internal electrode layers 23a and 23b. As a result, the dielectric layer 22c is sandwiched between the internal electrode layers 23a and 23b from above and below in the stacking direction and is laminated between the dielectric layers 22a and 22b. The dielectric layer 22c is mainly composed of the same ceramic material as the dielectric layers 22a and 22b. Note that the dielectric layer 22c is an example of a third dielectric layer.

[0056] As described above, in the laminate 2, three dielectric layers 22a to 22c having different average thicknesses Da to Dc are repeatedly laminated in the stacking direction. Therefore, when sintering the laminate 2 in the manufacture of the multilayer ceramic capacitor 1, a difference can be provided in the sinterability of each dielectric layer 22a to 22c. Specifically, due to the difference in the average thicknesses Da to Dc, for example, the shrinkage amount and the shrinkage timing of the dielectric layers 22a to 22c during sintering are different, so that the difference in the shrinkage amount between the dielectric regions such as the side margin portions 40 and 41 and the cover layers 20 and 21 adjacent to the periphery of the laminated region of the dielectric layers 22a to 22c and the internal electrode layers 23a and 23b and the laminate 2 is further reduced.

[0057] Therefore, compared with the case where the average thicknesses Da to Dc are the same, the stress caused by the shrinkage of each dielectric layer 22a to 22c can be dispersed, and the occurrence of cracks in the laminate 2 can be suppressed. Note that the average particle diameter of the ceramic particles contained in the dielectric layer 22c may be smaller than the average particle diameters of the ceramic particles 220a and 220b contained in the other dielectric layers 22a and 22b, respectively. In this case, as described above, the flatness and insulation characteristics of the dielectric layer 22c can be improved as compared with the case where the average particle diameters of the ceramic particles in the dielectric layers 22a to 22c are the same.

[0058] Further, the dielectric layer 22c also contains at least one kind of rare earth element that functions as a donor element, similar to the dielectric layers 22a and 22b. The concentration of the rare earth element with respect to the ceramic as the main component of the dielectric layer 22c is higher than the concentration of the rare earth element with respect to the ceramic as the main component of the dielectric layers 22a and 22b. For this reason, in the thin dielectric layer 22c, the generation amount and movement amount of oxygen defects are suppressed more than in the thick dielectric layers 22a and 22b. Therefore, compared with the case where the concentrations of the rare earth elements in the dielectric layers 22a to 22c are the same, the insulation characteristics of the multilayer ceramic capacitor 1 can be appropriately improved according to the average thicknesses of the dielectric layers 22a to 22c.

[0059] (Manufacturing process of multilayer ceramic capacitor) FIG. 7 is a flowchart showing an example of the manufacturing process of the multilayer ceramic capacitor 1. This manufacturing process is an example of a method for manufacturing multilayer ceramic electronic components.

[0060] (Multilayer sheet forming step) First, a multilayer sheet forming step St1 is performed. In this step, two green sheets that will become the dielectric layers 22a and 22b after the firing step are formed, and internal electrode patterns that will become the internal electrode layers 23a and 23b after the firing step are respectively formed on the two green sheets.

[0061] FIG. 8 is a cross-sectional view showing an example of the multilayer sheet forming step St1. FIG. 8 shows a cross-section along the stacking direction and the length direction of the laminate 2 after firing.

[0062] First, a green sheet forming step St10 is performed. In the green sheet forming step St10, a ceramic slurry is applied onto a substrate 8 to form a green sheet 7a. The ceramic slurry is applied onto the substrate 8 by, for example, a die coater method or a doctor blade method, and then dried. The substrate 8 is, for example, a PET (polyethylene terephthalate) film.

[0063] Ceramic slurry is obtained by wet-mixing a dielectric material obtained by adding various additive compounds (such as sintering aids) to ceramic powder, a binder such as polyvinyl butyral (PVB) resin, an organic solvent such as ethanol or toluene, and a plasticizer. As mentioned above, the additive compounds contain at least one rare earth element that functions as a donor element for the ceramic, which is the main component.

[0064] Rare earth elements added to ceramic slurries include Y (yttrium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), and Yb (ytterbium). Other additive compounds include Mg (magnesium), Mn (manganese), V (vanadium), Cr (chromium), and oxides or glasses of Co (cobalt), Ni, Li (lithium), B (boron), Na (sodium), K (potassium), and Si (silicon).

[0065] Next, an internal electrode pattern forming step St11 is performed. In the internal electrode pattern forming step St11, an internal electrode pattern 6a is formed by applying a conductive paste containing ceramic particles onto each of the green sheets 7a. The internal electrode pattern 6a becomes an internal electrode layer 23a after firing.

[0066] In the internal electrode pattern forming process St11, a metal conductive paste containing an organic binder for forming internal electrodes is printed on the green sheet 7a by gravure printing or the like, thereby forming a plurality of internal electrode patterns 6a at a distance from one another. Ceramic particles are added to the conductive paste as a co-material. The main component of the ceramic particles is not particularly limited, but is preferably the same as the main ceramic component of the dielectric layers 22a, 22b. The internal electrode patterns 6a may also be formed by vacuum deposition, such as sputtering, without being limited to printing.

[0067] Next, a green sheet forming step St12 is performed. In the green sheet forming step St12, a ceramic slurry produced in the same manner as the ceramic slurry used in the green sheet forming step St10 is applied to the green sheet 7a and the internal electrode pattern 6a to form a green sheet 7b. At this time, for example, the amount of ceramic slurry applied is adjusted so that the average thickness Tb of the green sheet 7b is smaller than the average thickness Ta of the green sheet 7a.

[0068] The ceramic slurry used in the green sheet forming step St12 also contains at least one rare earth element that functions as a donor element for the main ceramic component. In the green sheet forming step St12, the ceramic slurry is adjusted so that the concentration of the rare earth element relative to the main ceramic component of green sheet 7b is higher than the concentration of the rare earth element relative to the main ceramic component of green sheet 7a. This results in a higher concentration of the rare earth element contained in dielectric layer 22b than the concentration of the rare earth element contained in dielectric layer 22a.

[0069] Furthermore, the average particle size of the ceramic powder contained in the ceramic slurry used to form the green sheet 7a having the large average thickness Ta is larger than the average particle size of the ceramic powder contained in the ceramic slurry used to form the green sheet 7b having the small average thickness Tb. This allows the average particle size of the ceramic particles in the dielectric layer 22a to be larger than the average particle size of the ceramic particles in the dielectric layer 22b. Note that the green sheet 7a is an example of a first green sheet, and the green sheet 7b is an example of a second green sheet.

[0070] Next, the internal electrode pattern forming step St13 is performed. In the internal electrode pattern forming step St13, similar to the internal electrode pattern forming step St11, the internal electrode patterns 6b are formed by applying a conductive paste containing ceramic particles onto the green sheets 7b. The internal electrode patterns 6b become the internal electrode layers 23b after firing. The internal electrode patterns 6a, 6b are formed so as to be shifted from each other by half a pitch in the longitudinal direction. The internal electrode pattern 6b may be formed by a vacuum deposition method such as sputtering. The internal electrode pattern 6a is an example of a first electrode pattern, and the internal electrode pattern 6b is an example of a second electrode pattern.

[0071] The above steps form a plurality of laminated sheets 5. Thereafter, a laminated sheet peeling step St2 and a laminating and pressure bonding step St3 are carried out.

[0072] Fig. 9 is a cross-sectional view showing an example of the laminated sheet peeling step St2 and the laminating and pressure bonding step St3. Fig. 9 shows a cross section of the fired laminate 2 along the lamination direction and the length direction.

[0073] (Laminated sheet peeling process) After the laminated sheet forming step St1, a laminated sheet peeling step St2 is performed. In the laminated sheet peeling step St2, the laminated sheet 5 in which the green sheets 7a and 7b are laminated is peeled from the base material 8. At this time, the peeling device 80 applies an adsorption force f to the laminated sheet 5 from above and lifts it upward. Thereby, the laminated sheet 5 is peeled from the base material 8. The base material 8 is fixed to a conveyance table (not shown) or the like.

[0074] Thus, in the laminated sheet peeling step St2, since the green sheets 7a and 7b laminated on each other are peeled from the base material 8 together, even if the average thicknesses Ta and Tb of the green sheets 7a and 7b are reduced, the strength of the laminated sheet 5 is higher than that of the individual green sheets 7a and 7b, so the risk of damage is reduced. Therefore, the laminated ceramic capacitor 1 with the dielectric layers 22a and 22b thinned can be easily manufactured.

[0075] (Lamination and Pressing Step) Next, a lamination and pressing step St3 is performed. In the lamination and pressing step St3, a plurality of sets of green sheets 7a and 7b are laminated and pressed. That is, a plurality of laminated sheets 5 are laminated and pressed. At this time, the plurality of laminated sheets 5 are sandwiched from above and below in the lamination direction by other green sheets 7d and 7e that will become the cover layers 20 and 21 after firing, and pressing is performed. An internal electrode pattern 6b is formed on the surface of the lowermost green sheet 7e by the same method as in the internal electrode pattern forming step St13. Examples of the pressing means include, but are not limited to, a hydrostatic press.

[0076] (Cutting Step) Next, a cutting step St4 is performed. In the cutting step St4, the pressed green sheets 7a, 7b, 7d, and 7e are cut along multiple cutting lines extending vertically and horizontally at regular intervals, for example, using a blade. This separates the multiple laminate sheets 5 into multiple pre-fired laminates 2. FIG. 9 shows the cutting lines LW extending along the width direction of the laminate 2. Ends of the internal electrode patterns 6a and 6b are exposed on the end faces 2A and 2B, which are the cut surfaces of the laminate 2. Although not shown, when the multiple laminate sheets 5 are cut along cutting lines extending along the length direction of the laminate 2, ends of the internal electrode patterns 6a and 6b are exposed on the side faces 2E and 2F, which are the cut surfaces of the laminate 2.

[0077] (Side margin forming process) Next, a side margin forming step St5 is performed. In the side margin forming step St5, the side surfaces 2E and 2F of the laminate 2 are pressed against the green sheets for the side margins, and then the laminate 2 is moved away from the green sheets for the side margins. At this time, the parts of the green sheets remaining on the side surfaces 2E and 2F of the laminate 2 become side margin portions 40 and 41. As a result, the side margin portions 40 and 41 are formed on the side surfaces 2E and 2F of the laminate 2 before firing.

[0078] (polishing process) Next, a polishing step St6 is performed. In the polishing step St6, the laminate 2 is polished by a technique such as barrel polishing. As a result, the corners of the laminate 2 are rounded to form edge portions 200, 210.

[0079] (Firing process) Next, the firing process St7 is performed. In the firing process St7, after subjecting the laminate 2 before firing to a debinding treatment in an N2 atmosphere at 250 to 500 °C, firing is performed at a firing temperature of 1200 °C or higher for about 1 hour in a reducing atmosphere with an oxygen partial pressure of 0.003 (Pa), whereby each particle in the laminate 2 is sintered. As a result, in the laminate 2, the green sheets 7a, 7b, 7d, 7e become dielectric layers 22a, 22b and cover layers 20, 21, and the internal electrode patterns 6a, 6b become internal electrode layers 23a, 23b. Also, in the side margin forming process St5, a part of the green sheet remaining on the side surfaces 2E, 2F of the laminate 2 becomes side margin portions 40, 41.

[0080] Since the average thicknesses Ta, Tb of the green sheets 7a, 7b are different, in the firing process St7, as described above, a difference occurs in the sinterability of each dielectric layer 22a, 22b. For example, the shrinkage amount and the timing of shrinkage of the dielectric layers 22a, 22b are different. For this reason, the difference in the shrinkage amount between the side margin portions 40, 41 and the laminate 2 is reduced, and compared with the case where the average thicknesses Ta, Tb are the same, the stress due to the shrinkage of each dielectric layer 22a, 22b can be dispersed. Thereby, the occurrence of cracks in the laminate 2 is suppressed.

[0081] Also, in the firing process St7, in the region of the end margin portion 22m, the ceramic particles of the green sheet 7a and the ceramic particles of the green sheet 7b are mixed and grown, whereby ceramic particles 220m having a different particle size from the dielectric layers 22a, 22b are distributed.

[0082] In the firing process St7, since the raw material powder is exposed to a reducing atmosphere, oxygen defects occur in the main component ceramic. Here, since the concentration of the rare earth element with respect to the ceramic as the main component of the green sheet 7b is higher than the concentration of the rare earth element with respect to the ceramic as the main component of the green sheet 7a, the generation amount and the movement amount of the oxygen defects in the main component ceramic are appropriately suppressed according to the average thickness of the dielectric layers 22a, 22b, and the insulation characteristics thereof are improved.

[0083] (External electrode forming process) Next, the external electrode forming step St8 is performed. In the external electrode forming step St8, a conductive paste containing, for example, metal powder, glass frit, binder, and solvent is applied to the end faces 2A and 2B, the upper face 2C, the lower face 2D, and the side faces 2E and 2F of the laminate 2. After the conductive paste is applied, it is dried to form the external electrodes 3a and 3b. The binder and solvent evaporate when baked. Examples of methods for applying the conductive paste include sputtering and dipping.

[0084] This is how the multilayer ceramic capacitor 1 is manufactured. As described above, the manufacturing process for the multilayer ceramic capacitor 1 suppresses the occurrence of cracks and improves the insulating properties, thereby improving reliability.

[0085] (Manufacturing process of other multilayer ceramic capacitors) Next, the manufacturing process of the other multilayer ceramic capacitor 1a will be described. Here, only the differences from the manufacturing process of the multilayer ceramic capacitor 1 will be described for the laminated sheet forming step St1.

[0086] 10 is a cross-sectional view showing an example of a green sheet forming step St14 and an internal electrode pattern forming step St15 of another multilayer ceramic capacitor 1a. Fig. 10 shows a cross section of the fired laminate 2 along the lamination direction and the length direction.

[0087] After the internal electrode pattern forming step St13, a green sheet forming step St14 is performed. In the green sheet forming step St14, a ceramic slurry generated in the same manner as the ceramic slurry used in the green sheet forming step St10 is applied to the green sheet 7b and the internal electrode pattern 6b to form a green sheet 7c. The green sheet 7c becomes a dielectric layer 22c after firing. The green sheet 7c is an example of a third green sheet.

[0088] In the green sheet forming step St14, for example, the coating amount of the ceramic slurry is adjusted so that the average thickness Tc of the green sheet 7c becomes smaller than the average thickness Ta and Tb of the green sheets 7a and 7b. Note that the average particle size of the ceramic powder contained in the ceramic slurry used for forming the green sheet 7c may be smaller than the average particle size of the ceramic powder contained in the ceramic slurries used for forming the green sheets 7a and 7b. Thereby, the average particle size of the ceramic particles in the dielectric layer 22c can be made smaller than the average particle size of the ceramic particles in the dielectric layers 22a and 22b.

[0089] The ceramic slurry used in the green sheet forming step St14 also contains at least one rare earth element that functions as a donor element with respect to the main component ceramic. In the green sheet forming step St14, the ceramic slurry is adjusted so that the concentration of the rare earth element with respect to the main component ceramic of the green sheet 7c becomes higher than the concentration of the rare earth element with respect to the main component ceramic of the green sheets 7a and 7b. Thereby, the concentration of the rare earth element contained in the dielectric layer 22c becomes higher than the concentration of the rare earth element contained in the dielectric layers 22a and 22b.

[0090] Next, the internal electrode pattern forming step St15 is performed. In the internal electrode pattern forming step St15, in the same manner as in the internal electrode pattern forming step St11, the internal electrode pattern 6c is formed by applying a conductive paste added with ceramic particles onto the green sheet 7c. The internal electrode pattern 6c becomes the internal electrode layer 23a after firing. The internal electrode pattern 6c is formed so as to be shifted by a half pitch from the internal electrode pattern 6b in the length direction. Note that the internal electrode pattern 6c may be formed by a vacuum deposition method such as sputtering. Also, the internal electrode pattern 6c is an example of the third electrode pattern.

[0091] As described above, the laminated sheet 5a is formed. Also, a laminated sheet 5b, which is formed by laminating green sheets 7a to 7c with the internal electrode patterns 6a to 6c shifted by a half pitch, is also formed by the same method as described above. In the subsequent laminated sheet peeling step St2, the laminated sheets 5a and 5b with the green sheets 7a to 7c laminated thereon are peeled from the base material 8 by the method described above. Then, the laminating and pressing step St3 is performed.

[0092] FIG. 11 is a cross-sectional view showing an example of the laminating and pressing step St3 in another embodiment. FIG. 11 shows a cross-section along the laminating direction and the length direction of the fired laminate 2. In FIG. 11, the components common to FIG. 9 are denoted by the same reference numerals, and the description thereof is omitted.

[0093] In the laminating and pressing step St3, a plurality of sets of green sheets 7a to 7c are laminated and pressed by the method described above. Specifically, the laminated sheets 5a and 5b are alternately laminated and pressed. As a result, the green sheets 7a to 7c are repeatedly laminated in the laminating direction via the internal electrode patterns 6a to 6c.

[0094] In the subsequent cutting step St4, the pressed green sheets 7a to 7d are cut along a plurality of cut lines extending vertically and horizontally at regular intervals, for example, by a blade. As a result, the plurality of laminated sheets 5a and 5b are divided into a plurality of pre-fired laminates 2. The ends of the internal electrode patterns 6a to 6c are exposed on the cut surface of the laminate 2. Next, in the side margin forming step St5, side margins 40 and 41 are formed by attaching a part of the green sheet to the side surface in the width direction of the laminate 2. Next, in the polishing step St6, the laminate 2 is polished by a method such as barrel polishing.

[0095] Thereafter, in the firing step St7, the laminate 2 is fired by the same method as described above. Since the average thicknesses Ta to Tc of the green sheets 7a to 7c are different, in the firing step St7, as described above, differences occur in the sinterability of the dielectric layers 22a to 22c. For example, the shrinkage amounts and shrinkage timings of the dielectric layers 22a to 22c are different. Therefore, the difference in shrinkage amount between the side margin portions 40 and 41 and the laminate 2 is reduced, and compared with the case where the average thicknesses Ta to Tc are the same, the stress caused by the shrinkage of the dielectric layers 22a to 22c can be dispersed. As a result, the occurrence of cracks in the laminate 2 is suppressed, and the reliability of the multilayer ceramic capacitor 1a is improved.

[0096] Thereafter, in the external electrode forming step St8, external electrodes 3a and 3b are formed on the end faces 2A and 2B of the laminate 2. Thus, the multilayer ceramic capacitor 1a is manufactured.

[0097] As described above, the embodiments of the present invention have been described in detail. However, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Explanation of reference numerals

[0098] 1, 1a Multilayer ceramic capacitor 2, 50, 50a Laminate 3a, 3b External electrode 6a to 6c Internal electrode pattern 7a to 7d Green sheet 22a to 22c Dielectric layer 22m End margin portion 23a, 23b Internal electrode layer 220a, 220b, 220m Ceramic particle

Claims

1. A laminated body having a substantially rectangular parallelepiped shape in which a plurality of first dielectric layers, a plurality of second dielectric layers having an average thickness smaller than that of the plurality of first dielectric layers, and a plurality of internal electrode layers are laminated, wherein the first dielectric layers and the second dielectric layers are alternately laminated via the internal electrode layers and each contain at least one kind of rare earth element, and a concentration of the at least one kind of rare earth element with respect to a ceramic as a main component of the second dielectric layer is higher than a concentration of the at least one kind of rare earth element with respect to a ceramic as a main component of the first dielectric layer. A multilayer ceramic electronic component characterized by this.

2. The multilayer ceramic electronic component according to claim 1, wherein a concentration of the at least one kind of rare earth element with respect to a ceramic as a main component of the second dielectric layer is 1.08 times or more of a concentration of the at least one kind of rare earth element with respect to a ceramic as a main component of the first dielectric layer.

3. The multilayer ceramic electronic component according to claim 2, wherein a concentration of the at least one kind of rare earth element with respect to a ceramic as a main component of the second dielectric layer is 1.7 times or less of a concentration of the at least one kind of rare earth element with respect to a ceramic as a main component of the first dielectric layer.

4. The first dielectric layer and the second dielectric layer each further contain magnesium and manganese, and a total of concentrations of the at least one kind of rare earth element, the magnesium, and the manganese with respect to a ceramic as a main component of the second dielectric layer is 1.05 times or more of a total of concentrations of the at least one kind of rare earth element, the magnesium, and the manganese with respect to a ceramic as a main component of the first dielectric layer. The multilayer ceramic electronic component according to claim 1, characterized by this.

5. The multilayer ceramic electronic component according to claim 4, wherein a total of concentrations of the at least one kind of rare earth element, the magnesium, and the manganese with respect to a ceramic as a main component of the second dielectric layer is 1.5 times or less of a total of concentrations of the at least one kind of rare earth element, the magnesium, and the manganese with respect to a ceramic as a main component of the first dielectric layer.

6. The multilayer ceramic electronic component according to any one of claims 1 to 5, wherein an average particle diameter of ceramic particles contained in the first dielectric layer is larger than an average particle diameter of ceramic particles contained in the second dielectric layer.

7. a plurality of third dielectric layers each having an average thickness smaller than that of the second dielectric layers are further laminated on the laminate; the third dielectric layer is laminated between the first dielectric layer and the second dielectric layer via the internal electrode layer, and each contains the at least one rare earth element; 6. The multilayer ceramic electronic component according to claim 1, wherein the concentration of the at least one rare earth element in the ceramic that is the main component of the third dielectric layer is higher than the concentration of the at least one rare earth element in the ceramic that is the main component of the second dielectric layer.

8. forming a first green sheet by applying a ceramic slurry containing at least one rare earth element onto a substrate; forming a first internal electrode pattern on the first green sheet; forming a second green sheet by applying the ceramic slurry onto the first green sheet and the first internal electrode pattern so that the second green sheet has an average thickness smaller than that of the first green sheet; forming a second internal electrode pattern on the second green sheet; peeling the first green sheet and the second green sheet from the base material; a step of stacking and pressing a plurality of sets of the first green sheets and the second green sheets together; a step of dividing the plurality of pairs of the first green sheets and the second green sheets that have been pressed together into a plurality of laminates along the lamination direction; and firing the laminate, a step of forming the second green sheet by adjusting the ceramic slurry so that a concentration of the at least one rare earth element in a ceramic that is a main component of the second green sheet is higher than a concentration of the at least one rare earth element in a ceramic that is a main component of the first green sheet.

9. forming a first green sheet by applying a ceramic slurry containing at least one rare earth element onto a substrate; forming a first internal electrode pattern on the first green sheet; forming a second green sheet by applying the ceramic slurry onto the first green sheet and the first internal electrode pattern so that the second green sheet has an average thickness smaller than that of the first green sheet; forming a second internal electrode pattern on the second green sheet; forming a third green sheet by applying the ceramic slurry onto the second green sheet and the second internal electrode pattern so that the third green sheet has an average thickness smaller than that of the second green sheet; forming a third internal electrode pattern on the third green sheet; peeling the first green sheet, the second green sheet, and the third green sheet from the base material; a step of stacking and pressing a plurality of sets of the first green sheet, the second green sheet, and the third green sheet; a step of dividing the plurality of sets of the first green sheet, the second green sheet, and the third green sheet that have been pressed together into a plurality of laminates along a lamination direction; and firing the laminate, In the step of forming the second green sheet, the ceramic slurry is adjusted so that the concentration of the at least one rare earth element in the ceramic that is the main component of the second green sheet is higher than the concentration of the at least one rare earth element in the ceramic that is the main component of the first green sheet; a step of forming the third green sheet by adjusting the ceramic slurry so that a concentration of the at least one rare earth element in a ceramic that is a main component of the third green sheet is higher than a concentration of the at least one rare earth element in a ceramic that is a main component of the second green sheet.

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