JP2014222782A - Multilayer ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a possibility of occurrence of cracks in the vicinity of corners of an inner layer portion in a multilayer ceramic capacitor.SOLUTION: A multilayer ceramic capacitor 10 includes: a laminate 11 containing a plurality of dielectric layers 12 and a plurality of conductive layers 13; and a pair of external electrodes 14a and 14b, in which the laminate 11 contains an inner layer portion 11m, a first external layer portion 12b1, and a second external layer portion 12b2. If it is assumed that a gap length between the external electrode 14b and a first conductor layer 13z which is the conductive layer closest to the second external layer portion 12b2 is Lgap, and a length of a portion in which the external electrode 14b extends from an end of a reference end surface which is an end surface covered by the external electrode 14b of two end surfaces to an end of a first principal surface 111 or a second principal surface 112 with respect to a direction perpendicular to the reference end surface is k, k is no less than two times greater than Lgap and the maximum value of a thickness of the external electrode 14b in the portion in which the external electrode 14b covers the reference end surface is no less than 20 μm.

Description

  The present invention relates to a multilayer ceramic capacitor.

  Japanese Patent Application Laid-Open No. 2012-245851 (Patent Document 1) is a prior art document that discloses a multilayer ceramic capacitor that is intended to suppress the occurrence of cracks. In the multilayer ceramic capacitor described in Patent Document 1, the element body includes an internal electrode laminate (inner layer portion) in which a first internal electrode and a second internal electrode facing each other with a dielectric interposed therebetween, and an internal A first dielectric laminate (outer layer portion) and a second dielectric laminate (outer layer portion) sandwiching the electrode laminate (inner layer portion) from both sides in the lamination direction are included.

JP2012-2458581A

  Since the external electrode of the multilayer ceramic capacitor is generally formed by a method such as dipping, the thickness is not uniform. For example, it tends to be thin at a location near the corner of the laminate and thick at the center of each surface. When the external electrode is thick, the dielectric layer becomes brittle and cracks are likely to occur inside the laminate.

  If the multilayer ceramic capacitor has been used for a long time, heat shrinkage and deformation due to external force act repeatedly, and if there are such brittle portions in the dielectric layer, there is a possibility that cracks may occur. In particular, it is not preferable that cracks occur in the vicinity of the corners of the inner layer portion.

  Therefore, an object of the present invention is to provide a multilayer ceramic capacitor that can reduce the possibility of cracks occurring near the corners of the inner layer portion.

  To achieve the above object, a multilayer ceramic capacitor according to the present invention includes a plurality of dielectric layers and a plurality of conductor layers that are stacked, and a first main surface and a second main surface that are located on opposite sides in the stacking direction. A laminated body having a surface, and a pair of external electrodes provided on a part of the surface of the laminated body and electrically connected to at least some of the plurality of conductor layers. The stacked body has two end faces that connect the first main surface and the second main surface and are positioned on opposite sides of the stacked body, and the stacked body includes the plurality of end surfaces in the stacking direction. An inner layer portion including a conductor layer located closest to the first main surface among the conductor layers to a conductor layer located closest to the second main surface among the plurality of conductor layers; and the inner layer portion Including a first outer layer portion and a second outer layer portion sandwiched between each other, In the portion, the dielectric layers and the conductor layers are alternately laminated, and a part of the plurality of dielectric layers and the plurality of conductor layers are laminated, The pair of external electrodes cover the two end surfaces, respectively, and the first outer layer portion includes a dielectric layer located closest to the first main surface among the plurality of dielectric layers, The outer layer portion includes a dielectric layer located closest to the second main surface among the plurality of dielectric layers, and the conductor layer closest to the second outer layer portion among the conductor layers included in the inner layer portion. The first conductor layer is electrically connected to one external electrode of the pair of external electrodes but not electrically connected to the other external electrode, and the first conductor layer Lgap is the gap length in the extension direction of the first conductor layer between the layer and the other external electrode, and the other The external electrode covers the end of the main surface from the end of the first main surface or the second main surface of the reference end surface that is the end surface covered by the other of the two end surfaces. Where k is the length in the direction perpendicular to the reference end face, and k is at least twice Lgap, and the other external electrode covers the reference end face. The maximum thickness of the other external electrode is 20 μm or more.

  According to the present invention, since the area where the external electrode sandwiches and presses the laminated body is large, the force with which the external electrode compresses the laminated body in the laminating direction is increased, and cracks may occur near the corners of the inner layer portion. Can be reduced.

It is a perspective view of the multilayer ceramic capacitor in Embodiment 1 based on this invention. It is arrow sectional drawing regarding the II-II line | wire in FIG. It is arrow sectional drawing regarding the III-III line in FIG. It is explanatory drawing of the force which acts in the vicinity of the external electrode of the multilayer ceramic capacitor in Embodiment 1 based on this invention. It is explanatory drawing of the positional relationship of the vicinity of the corner | angular part of the inner layer part in the 1st example of a multilayer ceramic capacitor. It is explanatory drawing of the positional relationship of the vicinity of the corner | angular part of the inner layer part in the 2nd example of a multilayer ceramic capacitor. It is a flowchart of the manufacturing method of the multilayer ceramic capacitor in Embodiment 1 based on this invention. It is a disassembled perspective view which shows the laminated structure of the unit sheet group of the multilayer ceramic capacitor in Embodiment 1 based on this invention. It is sectional drawing of the multilayer ceramic capacitor in Embodiment 2 based on this invention.

(Embodiment 1)
(Constitution)
With reference to FIGS. 1-3, the multilayer ceramic capacitor in Embodiment 1 based on this invention is demonstrated. FIG. 1 shows a perspective view of the multilayer ceramic capacitor 10 in the present embodiment. FIG. 2 shows a cross-sectional view taken along the line II-II in FIG. FIG. 3 shows a cross-sectional view taken along the line III-III in FIG.

  A multilayer ceramic capacitor 10 according to the present embodiment includes a plurality of dielectric layers 12 and a plurality of conductor layers 13 that are stacked, and a first main surface 111 and a second main surface 112 that are located on opposite sides in the stacking direction. A pair of external electrodes 14a provided on a part of the surface of the laminate 11 and electrically connected to at least some of the conductor layers 13 of the plurality of conductor layers 13. 14b. Since FIG. 3 is a cross section cut at a place where the external electrodes 14a and 14b are not present, the external electrode 14a is visible in the back in FIG. The stacked body 11 has two end surfaces 113 and 114 that connect the first main surface 111 and the second main surface 112 and are positioned on opposite sides of the stacked body 11. The stacked body 11 is positioned in the stacking direction from the conductor layer 13 positioned closest to the first main surface 111 among the plurality of conductor layers 13 to the second main surface 112 side of the plurality of conductor layers 13. An inner layer portion 11m including up to the conductor layer 13 and a first outer layer portion 12b1 and a second outer layer portion 12b2 sandwiching the inner layer portion 11m therebetween. In the inner layer portion 11m, the dielectric layers 12 and the plurality of conductor layers 13 out of the plurality of dielectric layers 12 are in a state where the dielectric layers 12 and the conductor layers 13 are alternately stacked. Are stacked. The pair of external electrodes 14a and 14b cover the two end surfaces 113 and 114, respectively. The first outer layer portion 12b1 includes a dielectric layer located closest to the first main surface among the plurality of dielectric layers. The second outer layer portion 12b2 includes the dielectric layer 12 located closest to the second major surface 112 among the plurality of dielectric layers 12.

  The first conductor layer 13z, which is the conductor layer 13 closest to the second outer layer part 12b2 among the conductor layers 13 included in the inner layer part 11m, is connected to one external electrode 14a of the pair of external electrodes 14a and 14b. Although it is electrically connected, it is not electrically connected to the other external electrode 14b.

  The gap length in the extending direction of the first conductor layer 13z between the first conductor layer 13z and the other external electrode 14b is Lgap. The other external electrode 14b uses the end surface covered by the other external electrode 14b of the two end surfaces 113 and 114 as a reference end surface. In this case, the end surface 114 is a reference end surface. A direction perpendicular to the reference end surface of the portion where the other external electrode 14b extends from the end on the first main surface 111 or the second main surface 112 side of the reference end surface so as to cover the end of the main surface Let k be the length of. k is more than twice Lgap. The maximum value of the thickness of the other external electrode 14b in the portion where the other external electrode 14b covers the reference end face is 20 μm or more.

The thickness of the inner layer portion 11m is T _1. The thickness of the first outer layer portion 12b1 is h _1. The thickness of the second outer layer portion 12b2 is h _2.

(Action / Effect)
In the present embodiment, the length k of the portion where the external electrode 14b extends to cover the end of the first main surface 111 or the second main surface 112 is as large as twice or more of Lgap. As shown in FIG. 4, the area where the external electrode 14b sandwiches and presses the multilayer body 11 is increased by that much, and the effect of the external electrode 14b compressing the multilayer body 11 in the stacking direction is great. Thereby, possibility that a crack will arise in the vicinity of the corner of the inner layer part can be reduced.

  The crack generated near the corner of the inner layer portion is a crack that is considered to be generated between the end of the first conductor layer 13z and the external electrode 14b in FIGS. As a result of consideration, the inventors found the following as the cause of the occurrence of cracks.

The glass component tends to diffuse from the external electrode 14 b to the dielectric layer 12. As the glass component diffuses into the dielectric layer 12, the dielectric layer 12 has a property of becoming brittle. When h ₂ is increased as shown in FIG. 6 as compared with FIG. 5, the thickness of the external electrode 14b at the position on the extension of the first conductive layer 13z is increased even if Lgap is the same. That is, the thickness A increases from the thickness A in FIG. 5 to the thickness B in FIG. As the thickness increases, a large amount of glass component diffuses at this location. Therefore, cracks are likely to occur inside the multilayer body 11 at locations where the external electrodes 14b are thick.

  In the present embodiment, since the maximum value of the thickness of the other external electrode 14b in the portion where the external electrode 14b covers the reference end face is 20 μm or more, the reference end face is made of glass toward the internal dielectric layer 12. This means that there are places where the components are likely to diffuse. In this embodiment, the dielectric layer 12 has such a factor that it becomes brittle, but since the length k is sufficiently large, cracks inside the multilayer body 11 are caused by the pressing effect. Occurrence can be prevented.

  The thickness of the other external electrode 14b on the extension of the first conductor layer 13z is the other on the extension of the conductor layer 13 closest to the first outer layer portion 12b1 among the conductor layers 13 included in the inner layer portion 11m. The thickness of the external electrode 14b is preferably larger than the thickness of the external electrode 14b. Thus, when the thickness of the external electrode 14b is asymmetric in the vertical direction for the inner layer portion 11m, there is a concern about the occurrence of cracks near the corner of the inner layer portion 11m on the side where the thickness of the external electrode 14b is large. In such a case, the effect of the present invention can be remarkably enjoyed by applying the present invention.

  The thickness of the second outer layer portion 12b2 is preferably 80 μm or more. When the second outer layer portion 12b2 is thick as described above, there is a high probability that the thickness of the external electrode 14b is increased in the vicinity of the corner of the inner layer portion. However, by applying the present invention to such a case, the present invention is applied. The effects of the invention can be remarkably enjoyed.

  The second outer layer portion 12b2 is preferably thicker than the first outer layer portion 12b1. Thus, when the thickness of the outer layer portion is different in the upper and lower direction in the stacking direction of the inner layer portion 11m, and the second outer layer portion 12b2 is thicker, the corner on the side closer to the second outer layer portion 12b2 of the inner layer portion 11m. However, by applying the present invention in such a case, the effect of the present invention can be remarkably enjoyed.

  When the thickness of the second outer layer portion 12b2 is 80 μm or more, the thickness of the first outer layer portion 12b1 is further preferably 80 μm or more. When both the first outer layer portion 12b1 and the second outer layer portion 12b2 are thick in this way, the thickness of the external electrode 14b tends to increase in the vicinity of the corner of the inner layer portion 11m. In such a case, the effect of the present invention can be remarkably enjoyed by applying the present invention.

(Production method)
A method for manufacturing multilayer ceramic capacitor 10 in the present embodiment will be described. A flowchart of the method for manufacturing the multilayer ceramic capacitor 10 is shown in FIG.

  In addition, the manufacturing method of the multilayer ceramic capacitor shown below manufactures a mother laminated body by batch processing until the middle stage of the manufacturing process, and then divides the mother laminated body into individual pieces. In this method, a plurality of multilayer ceramic capacitors 10 are simultaneously produced in large quantities by further processing the processed soft laminate.

  As shown in FIG. 7, when the multilayer ceramic capacitor 10 is manufactured, first, a first ceramic slurry is prepared (step S11). Specifically, ceramic powder, a binder, a solvent, and the like are mixed at a predetermined blending ratio, thereby forming a first ceramic slurry.

  Next, a first ceramic green sheet is formed (step S12). Specifically, the first ceramic green sheet is manufactured by forming the first ceramic slurry into a sheet shape using a die coater, a gravure coater, a micro gravure coater or the like on the carrier film.

  Next, a mother sheet is formed (step S13). Specifically, the conductive paste is printed on the first ceramic green sheet by using a screen printing method or a gravure printing method so that the conductive paste has a predetermined pattern. A mother sheet provided with a conductive pattern is formed.

  Here, the mother sheet to be manufactured will be described. FIG. 8 is an exploded perspective view showing the laminated structure of the unit sheet group of the multilayer ceramic capacitor multilayer body 11 according to Embodiment 1 of the present invention.

  As shown in FIG. 8, the laminate 11 is manufactured using a unit sheet group including a plurality of unit sheets 120a, 130a, and 130b having different configurations, and more specifically, a plurality of unit sheets 120a, 130b having different configurations. 130a and 130b are laminated in a predetermined order, and are manufactured by pressure bonding and firing.

  The unit sheet 120a is composed only of the ceramic substrate 12xr having no conductive pattern formed on the surface thereof. The unit sheet 120a becomes a part constituting the dielectric layer 12 of the first outer layer part 12b1 or the second outer layer part 12b2 after firing.

  The unit sheets 130a and 130b are obtained by forming a conductive pattern 13r having a predetermined shape on the surface of the ceramic substrate 12xr. The conductive pattern 13r in the unit sheets 130a and 130b becomes a part constituting the conductor layer 13 of the inner layer part 11m after firing. Moreover, the ceramic base material 12xr of the unit sheets 130a and 130b becomes a portion constituting the first dielectric layer 12x of the inner layer portion 11m after firing.

  The mother sheet has a layout in which each of the unit sheets 130a and 130b shown in FIG. 8 is laid out in a plural number so that unit sheets of the same shape are arranged in a matrix in the form of each unit sheet as a unit unit. It is.

  Since the unit sheet 130a and the unit sheet 130b have the same shape, as the mother sheet including them, those having the same conductive pattern can be used, and the mother having the same conductive pattern in the mother sheet laminating process described later. By laminating the sheets by shifting by half a pitch, the laminated structure of the unit sheets 130a and 130b shown in FIG. 8 can be obtained.

  In addition to the mother sheet having the conductive pattern 13r, a first ceramic green sheet manufactured without forming the conductive pattern 13r is also prepared as the mother sheet.

  Next, a mother sheet is laminated (step S14). Specifically, by stacking a plurality of mother sheets according to a predetermined rule, the unit units in the stacked mother sheet group have the stacked structure shown in FIG. 8 in the stacking direction. Placed in.

Next, the mother sheet group is pressure-bonded (step S15).
Next, the mother laminate is divided (step S25). Specifically, the mother laminated body is divided into a matrix by pressing or dicing, whereby the soft laminated body is cut out.

  Next, the soft laminate is fired (step S26). Specifically, the cut soft laminate is heated to a predetermined temperature, and the ceramic dielectric material and the conductor material are fired. The firing temperature is appropriately set according to the types of the ceramic dielectric material and the conductor material, and is set, for example, within a range of 900 ° C. or higher and 1300 ° C. or lower.

  Next, barrel polishing of the soft laminate is performed (step S27). Specifically, the soft laminated body after firing is enclosed in a small box called a barrel together with a media ball having a hardness higher than that of the ceramic material, and the soft laminated body is polished by rotating the barrel. As a result, the outer surface (especially corners and ridges) of the soft laminate is rounded, and the laminate 11 is formed.

  Next, an external electrode is formed (step S28). Specifically, a metal film is formed by applying a conductive paste to each end including the two end surfaces of the laminate, and after the metal film is fired, Ni plating and Sn plating are sequentially applied to the metal film. By being applied, a pair of external electrodes 14a and 14b are formed on the outer surface of the laminate.

  Through the above series of steps, the multilayer ceramic capacitor 10 having the structure shown in the present embodiment is manufactured.

(Embodiment 2)
(Constitution)
With reference to FIG. 9, the multilayer ceramic capacitor in Embodiment 2 based on this invention is demonstrated. FIG. 9 shows a cross-sectional view of the multilayer ceramic capacitor 10i in the present embodiment.

  The basic configuration of the multilayer ceramic capacitor 10i in the present embodiment is the same as that of the multilayer ceramic capacitor 10 described in the first embodiment, but the breakdown of the second outer layer portion 12b2 is different. In the present embodiment, the second outer layer portion 12b2 includes an inner outer layer portion 12b21 and an outer outer layer portion 12b22. The first outer layer portion 12b1 includes a first dielectric layer 12x. The second outer layer portion 12b2 includes a first dielectric layer 12x and a second dielectric layer 12y. The second dielectric layer 12y is different in composition from the first dielectric layer 12x. The boundary between the first dielectric layer 12x and the second dielectric layer 12y is a boundary surface 12z.

(Action / Effect)
Also in the present embodiment, the same effect as in the first embodiment can be obtained. In the present embodiment, only the second outer layer portion 12b2 includes the second dielectric layer 12y having a different composition. However, the first outer layer portion 12b1 also includes the second dielectric layer having such a different composition. 12y may be included.

(Experiment)
A fired laminate was prepared in which the dimension in the L direction was 1.6 mm, the dimension in the W direction was 0.8 mm, and the thickness of the second outer layer portion was different in several ways. An external electrode was formed by applying a conductive paste containing a glass component to this laminate and baking it. As shown in Table 1, conditions 1 to 15 were prepared by changing some parameters, and 10 samples were produced for each condition. About each sample, LT section which passes along the center of the laminated body in which the external electrode was formed was grind | polished and exposed, and the presence or absence of the structural defect was confirmed with the optical microscope.

  The evaluation was “bad” when 10 or more samples having a structural defect were present among the 10 samples produced under the conditions, and “good” when no sample had a structural defect.

(Experimental result)
The results of the experiment are as shown in Table 1. In the samples of conditions 1 to 12, the structural defect was evaluated as good, whereas in the samples of conditions 13 to 15, it was bad. Conditions 1-10 satisfy the relationship k ≧ 2 × Lgap, and Conditions 11-15 satisfy the relationship k <2 × Lgap.

  From this result, it is understood that when k <2 × Lgap, structural defects occurred when the thickness of the external electrode was 20 μm or more. On the other hand, in the case of k ≧ 2 × Lgap, it can be seen that no structural defect occurred even when the thickness of the external electrode was 20 μm or more.

  In addition, the said embodiment disclosed this time is an illustration in all the points, Comprising: It is not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and includes all modifications within the scope and meaning equivalent to the terms of the claims.

  10, 10i multilayer ceramic capacitor, 11 multilayer body, 11m inner layer part, 11p partly laminated body, 12 dielectric layer, 12b1 first outer layer part, 12b2 second outer layer part, 12b21 inner outer layer part, 12b22 outer outer layer part, 12x first 1 dielectric layer, 12y second dielectric layer, 12z interface, 12xr ceramic substrate, 13 conductor layer, 13r conductive pattern, 13z first conductor layer, 14a (one external electrode), 14b (the other) External electrode, 111 first main surface, 112 second main surface, 113 end surface, 114 end surface (reference end surface), 115, 116 side surface, 120a, 130a, 130b unit sheet.

Claims (5)

A laminate including a plurality of dielectric layers and a plurality of conductor layers laminated, and having a first principal surface and a second principal surface located on opposite sides in the lamination direction;
A pair of external electrodes provided on a part of the surface of the laminated body and electrically connected to at least some of the plurality of conductor layers;
The laminate has two end faces that connect the first principal surface and the second principal surface and are positioned on opposite sides of the laminate,
In the stacking direction, the stacked body includes a conductor layer located closest to the first principal surface among the plurality of conductor layers, and a conductor located closest to the second principal surface among the plurality of conductor layers. An inner layer part including up to the body layer, and a first outer layer part and a second outer layer part sandwiching the inner layer part between each other,
In the inner layer portion, a part of the plurality of dielectric layers and the plurality of conductor layers are stacked in a state where the dielectric layers and the conductor layers are alternately stacked. And
The pair of external electrodes respectively covers the two end surfaces;
The first outer layer portion includes a dielectric layer located closest to the first main surface of the plurality of dielectric layers, and the second outer layer portion is the second main surface of the plurality of dielectric layers. A dielectric layer located on the side,
The first conductor layer, which is the conductor layer closest to the second outer layer portion among the conductor layers included in the inner layer portion, is electrically connected to one of the pair of external electrodes. Is not electrically connected to the other external electrode,
The gap length in the extending direction of the first conductor layer between the first conductor layer and the other external electrode is Lgap, and the other external electrode is the other end of the two end faces. The reference end surface of the portion extending so as to cover the end portion of the main surface from the end of the first main surface or the second main surface side of the reference end surface which is the end surface covered by the external electrode If the length in the vertical direction is k, k is more than twice Lgap,
The multilayer ceramic capacitor, wherein the maximum value of the thickness of the other external electrode in a portion where the other external electrode covers the reference end face is 20 μm or more.   The thickness of the other external electrode on the extension of the first conductor layer is such that the other external electrode on the extension of the conductor layer closest to the first outer layer portion among the conductor layers included in the inner layer portion. The multilayer ceramic capacitor according to claim 1, wherein the multilayer ceramic capacitor is larger than the thickness of the multilayer ceramic capacitor.   The multilayer ceramic capacitor according to claim 1 or 2, wherein the thickness of the second outer layer portion is 80 µm or more.   The multilayer ceramic capacitor according to claim 1, wherein the second outer layer portion is thicker than the first outer layer portion.   The multilayer ceramic capacitor according to claim 3, wherein the first outer layer portion has a thickness of 80 μm or more.

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