Patent Application
20240355550
The present invention relates to a multilayer ceramic capacitor.
A capacitor has been provided with the aim to reduce cracks in an element or to reduce separation of an element and an external electrode from each other. Japanese Unexamined Patent Application, Publication No. 2018-170355 discloses a capacitor in which the porosity of a sintered electrode layer of an external electrode is adjusted to accomplish the aim.
Unfortunately, while an increase in the capacitance of a capacitor results in an increase in the number of electrode layers stacked, delamination is not adequately reduced.
Example embodiments of the present invention provide capacitors that each further reduce delamination.
A multilayer ceramic capacitor according to an example embodiment of the present invention including a multilayer body including a plurality of dielectric layers stacked, and a plurality of internal electrode layers each stacked on an associated one of the dielectric layers, the multilayer body including first and second main surfaces that face each other in a lamination direction, first and second end surfaces that face each other in a length direction orthogonal or substantially orthogonal to the lamination direction, and first and second lateral surfaces that face each other in a width direction orthogonal or substantially orthogonal to the lamination direction and the length direction, the plurality of internal electrode layers further including a plurality of first internal electrode layers on the plurality of dielectric layers, the first internal electrode layers extending to the first and second end surfaces, and a plurality of second internal electrode layers on the plurality of dielectric layers, the second internal electrode layers extending to the first and second lateral surfaces, a first external electrode on the first end surface, the first external electrode being connected to the first internal electrode layers, a second external electrode on the second end surface, the second external electrode being connected to the first internal electrode layers, a third external electrode on the first lateral surface, the third external electrode being connected to the second internal electrode layers, and a fourth external electrode on the second lateral surface, the fourth external electrode being connected to the second internal electrode layers, the first internal electrode layers each including a first counter electrode portion that faces an associated one of the second internal electrode layers with one of the dielectric layers interposed between the first counter electrode portion and the associated one of the second internal electrode layers, a first extension portion extending from the first counter electrode portion to the first end surface, and a second extension portion extending from the first counter electrode portion to the second end surface, the second internal electrode layers each including a second counter electrode portion that faces an associated one of the first internal electrode layers with one of the dielectric layers interposed between the second counter electrode portion and the associated one of the first internal electrode layers, a third extension portion extending from the second counter electrode portion to the first lateral surface, and a fourth extension portion extending from the second counter electrode portion to the second lateral surface, a dimension A of each of the first and second extension portions in the width direction being less than a dimension B of the first counter electrode portion in the width direction, a dimension W1 from a side of each of the first and second extension portions near the first lateral surface to the first lateral surface in the width direction and a dimension W2 from a side of each of the first and second extension portions near the second lateral surface to the second lateral surface in the width direction being each greater than the dimension A of each of the first and second extension portions in the width direction.
According to example embodiments of the present invention, it is possible to provide capacitors in which delamination is further reduced.
The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings.
Example embodiments of the present invention will be described below with reference to the accompanying drawings. The same reference numerals are used to represent identical or equivalent elements in figures.
An outline of the structure of a multilayer ceramic capacitor 1 will be described with reference to
As illustrated in
The external electrodes will be described with reference to
The first external electrode 3 is located on the first end surface LS1 of the multilayer body 2. The first external electrode 3 extends from over the first end surface LS1 to over a portion of the first main surface TS1, a portion of the second main surface TS2, a portion of the first lateral surface WS1, and a portion of the second lateral surface WS2. A portion of the first external electrode 3 located on the first end surface LS1 of the multilayer body 2 is referred to as the “first end surface electrode portion 3c”, portions of the first external electrode 3 covering the portion of the first main surface TS1 and the portion of the second main surface TS2 are referred to as the “first main surface electrode portions 3a”, and portions of the first external electrode 3 covering the portion of the first lateral surface WS1 and the portion of the second lateral surface WS2 are referred to as the “first lateral surface electrode portions 3b”.
The second external electrode 4 is located on the second end surface LS2 of the multilayer body 2. The second external electrode 4 has a structure similar to that of the first external electrode 3. Specifically, the second external electrode 4 extends from over the second end surface LS2 to over a portion of the first main surface TS1, a portion of the second main surface TS2, a portion of the first lateral surface WS1, and a portion of the second lateral surface WS2. A portion of the second external electrode 4 located on the second end surface LS2 of the multilayer body 2 is referred to as the “second end surface electrode portion 4c”, portions of the second external electrode 4 covering the portion of the first main surface TS1 and the portion of the second main surface TS2 are referred to as the “second main surface electrode portions 4a”, and portions of the second external electrode 4 covering the portion of the first lateral surface WS1 and the portion of the second lateral surface WS2 are referred to as the “second lateral surface electrode portions 4b”.
The third external electrode 5 is located on the first lateral surface WS1 of the multilayer body 2. The third external electrode 5 is located on a portion of the first lateral surface WS1 in the length direction L (specifically, on a central portion of the first lateral surface WS1 in the length direction L) without being located on the entire first lateral surface WS1. The third external electrode 5 extends from over the portion of the first lateral surface WS1 to over a portion of the first main surface TS1 and a portion of the second main surface TS2. A portion of the third external electrode 5 located on the first lateral surface WS1 of the multilayer body 2 is referred to as the “third lateral surface electrode portion 5b”, and portions of the third external electrode 5 covering the portion of the first main surface TS1 and the portion of the second main surface TS2 are referred to as the “third main surface electrode portions 5a”.
The fourth external electrode 6 is located on the second lateral surface WS2 of the multilayer body 2. The fourth external electrode 6 has a structure similar to that of the third external electrode 5. Specifically, the fourth external electrode 6 is located on a portion of the second lateral surface WS2 in the length direction L (specifically, on a central portion of the second lateral surface WS2 in the length direction L) without being located on the entire second lateral surface WS2. The fourth external electrode 6 extends from over the portion of the second lateral surface WS2 to over a portion of the first main surface TS1 and a portion of the second main surface TS2. A portion of the fourth external electrode 6 located on the second lateral surface WS2 of the multilayer body 2 is referred to as the “fourth lateral surface electrode portion 6b”, and portions of the fourth external electrode 6 covering the portion of the first main surface TS1 and the portion of the second main surface TS2 are referred to as the “fourth main surface electrode portions 6a”.
Internal electrode layers will be described with reference to
The planar structures of each first internal electrode layer 8 and each second internal electrode layer 9 will be described with reference to
As illustrated in
The extension portions extend from the associated counter electrode portions to connect the counter electrode portions to the associated external electrodes. The extension portions of the first internal electrode layers 8 are different in position from those of the second internal electrode layers 9. Each first internal electrode layer 8 has its extension portions positioned so as to be each connected to an associated one of the first and second external electrodes 3 and 4. In contrast, each second internal electrode layer 9 has its extension portions positioned so as to be each connected to an associated one of the third and fourth external electrodes 5 and 6. The extension portions of the first internal electrode layer 8 are referred to as the “first and second extension portions 8b and 8c”, and the extension portions of the second internal electrode layer 9 are referred to as the “third and fourth extension portions 9b and 9c”. The first extension portion 8b connects the first counter electrode portion 8a and the first end surface electrode portion 3c together. The second extension portion 8c connects the first counter electrode portion 8a and the second end surface electrode portion 4c together. The third extension portion 9b connects the second counter electrode portion 9a and the third lateral surface electrode portion 5b together. The fourth extension portion 9c connects the second counter electrode portion 9a and the fourth lateral surface electrode portion 6b together.
An LT cross section of the multilayer ceramic capacitor 1 will be described with reference to
A WT cross section of the multilayer ceramic capacitor 1 will be described with reference to
As described above, the first internal electrode layers 8 are connected to the first and second external electrodes 3 and 4. The first and second external electrodes 3 and 4 face each other in the length direction L, and each have the electrode portions located on five different surfaces of the multilayer body 2. In contrast, the second internal electrode layers 9 are connected to the third and fourth external electrodes 5 and 6. The third and fourth external electrodes 5 and 6 face each other in the width direction W, and each have the electrode portions located on three different surfaces of the multilayer body 2. Such a configuration allows the multilayer ceramic capacitor 1 to function as a three-terminal capacitor. The first internal electrode layers 8 function as feedthrough electrodes of the three-terminal capacitor, and the second internal electrode layers 9 function as ground electrodes of the three-terminal capacitor.
The multilayer ceramic capacitor 1 according to the example embodiment of the present invention is characterized by the width of the extension portions. This will be described with reference to
In
In the multilayer ceramic capacitor 1 of this example embodiment, the dimension A is less than the dimension B, and is less than each of the dimensions W1 and W2. In other words, the expressions “dimension A<dimension B”, “dimension A<dimension W1”, and “dimension A<dimension W2” are satisfied.
Thus, separation of the first and second extension portions 8b and 8c from the adjacent dielectric layers 7 near the first and second extension portions 8b and 8c can be reduced. Furthermore, separation of portions of the dielectric layers 7 apart from the first and second extension portions 8b and 8c from one another can be reduced.
A region surrounded by each of the dotted lines in
The first and second extension portions 8b and 8c of the multilayer ceramic capacitor 1 of this example embodiment have their width in the width direction W reduced. This can reduce internal structural defects, such as separations, in the feedthrough extension region R1.
A comparison between the effective region R2 and the feedthrough extension region R1 shows that delamination is more likely to occur in the feedthrough extension region R1 than in the effective region R2. The term delamination as used herein refers to separation of an internal electrode layer and a dielectric layer in contact with each other in the lamination direction T from each other, separation of dielectric layers in contact with each other in the lamination direction T from each other, or any similar type of separation. As described above, the first counter electrode portions 8a have the same planar structure as the second counter electrode portions 9a. Thus, in the effective region R2, the multilayer body 2 has a uniform or substantially uniform thickness. In addition, the effective region R2 occupies a large region of the WL cross section of the multilayer body 2. These causes make it difficult to produce delamination in the effective region R2. In contrast, each feedthrough extension region R1 includes a portion including the first extension portions 8b or the second extension portions 8c, and a portion including only the dielectric layers 7 stacked. Thus, in the feedthrough extension region R1, the multilayer body 2 is less likely to have a uniform thickness. The proportion of the feedthrough extension region R1 in the WL cross section of the multilayer body 2 is less than that of the effective region R2. Thus, the internal stress produced in the effective region R2 tends to be greater than the interlayer adhesive strength in the feedthrough extension region R1. This makes it easier to produce delamination in the feedthrough extension region R1.
The greater the number of the internal electrode layers stacked (i.e., the number of stacked layers) is, the more easily delamination occurs. One of the reasons for this is that the internal stress produced in the effective region R2 further increases. Another one of the reasons is that the multilayer body 2 is more likely to have a non-uniform thickness in the feedthrough extension region R1. There is a trend to increase the number of stacked layers to increase the capacitance of the multilayer ceramic capacitor 1. For example, the combined total number of the first internal electrode layers 8 and the second internal electrode layers 9 stacked may be 200 or more. This makes it easier to produce delamination in the feedthrough extension region R1.
The first and second extension portions 8b and 8c of each first internal electrode layer 8 are more likely to undergo delamination than the third and fourth extension portions 9b and 9c of each second internal electrode layer 9 are. The reason for this is that regions of the three-terminal capacitor located on both sides of each of extension portions of each feedthrough electrode (i.e., the first and second extension portions 8b and 8c) and including only the dielectric layers 7 stacked have a smaller area in the planar structure than those located on both sides of each of extension portions of each ground electrode (i.e., the third and fourth extension portions 9b and 9c).
The first and second extension portions 8b and 8c of the multilayer ceramic capacitor 1 of this example embodiment have their dimension in the width direction W reduced. Thus, even if the number of stacked layers is great, delamination is less likely to occur in the feedthrough extension region R1. Sufficiently large regions including only the dielectric layers 7 stacked can be provided on both sides of each of the first and second extension portions 8b and 8c in the width direction W. This can improve the interlayer adhesion, and can enhance the interlayer adhesive strength.
Note that the above-described delamination may occur in various situations. For example, in the process of fabricating a multilayer ceramic capacitor 1, in the process of mounting the multilayer ceramic capacitor 1 on a board, or during the use of the multilayer ceramic capacitor 1 as a portion of a product, delamination may occur.
In addition, the dimensions W1 and W2 are preferably greater than or equal to about 0.375×W′, for example, where W′ represents the dimension of the multilayer body 2 in the width direction W. The dimension A is preferably equal to or less than about 0.25×W′, for example. In other words, the expressions “W1≥0.375×W′” and “W2≥0.375×W′” are preferably satisfied, for example. The expression “A≤0.25×W′” is preferably satisfied, for example. These expressions will be described with reference to
If the expression “½A≤⅛W′” is set to be satisfied, for example, the expression “W1≥0.375×W′” is derived from the expression “W1=½W′−½A”. A preferable range of the dimension W2 is expressed by “W2≥0.375×W′”, for example, just like that of the dimension W1.
Furthermore, if the expression “½A≤⅛W′” is set to be satisfied, the expression “A ¼W′” is derived, and thus a preferable range of the dimension A is expressed by “A≤0.25W′”, for example.
Each second internal electrode layer 9 will be described with reference to
The dimension A is preferably equal to or less than about 1.5 times the dimension C, for example. In other words, the expression “the dimension A<1.5C” is preferably satisfied, for example. Thus, the ratio of the dimension of each of the first and second extension portions 8b and 8c in the width direction W to that of each of the third and fourth extension portions 9b and 9c in the length direction L can be relatively lower. This allows the internal stress produced in the effective region R2 to be moderately shared by, and to be distributed among, the feedthrough extension region R1 and the ground extension regions R3. This can further reduce delamination.
The relation between the above-described dimensions and delamination will be described with reference to
As shown in the second example, if the dimension A was less than the dimension B, and the dimensions W1 and W2 were each greater than the dimension A, the result of evaluating delamination was “excellent”. In contrast, as shown in the first comparative example, if the dimension A was not less than the dimension B, and the dimensions W1 and W2 were not each greater than the dimension A, the result of evaluating delamination was a “fail”.
A comparison between the second example and the fourth example shows that if the dimensions W1 and W2 were each greater than or equal to about 0.375×W′ (i.e., in the second example), the result of evaluating delamination was better than if the dimensions W1 and W2 were not each greater than or equal to about 0.375×W′ (i.e., than in the fourth example), for example.
A comparison between the second example and the fourth example shows that if the dimension A was less than or equal to about 0.25×W′ (i.e., in the second example), the result of evaluating delamination was better than if the dimension A was not less than or equal to about 0.25×W′ (i.e., than in the fourth example), for example.
A comparison between the second example and the third example shows that if the dimension C was less than the dimension D (i.e., in the second example), the result of evaluating delamination was better than if the dimension C was not less than the dimension D (i.e., than in the third example).
A comparison between the second example and the fifth example shows that if the dimension A was less than about 1.5 times the dimension C (i.e., in the second example), the result of evaluating delamination was better than if the dimension A was not less than about 1.5 times the dimension C (i.e., than in the fifth example), for example.
Materials and other elements of components will now be described.
The plurality of dielectric layers 7 are made of a dielectric material. The dielectric material may be a dielectric ceramic including an ingredient, such as BaTiO3, CaTiO3, SrTiO3, or CaZrO3. The dielectric material may include an accessory ingredient, such as a Mn compound, an Fe compound, a Cr compound, a Co compound, or a Ni compound, added to these main ingredients.
The thickness of the dielectric layers 7 is not specifically limited, but is preferably greater than or equal to about 0.5 μm and equal to or less than about 3.0 μm, for example. The number of the dielectric layers 7 is not specifically limited, but is preferably 200 or more, for example.
The first internal electrode layers 8 and the second internal electrode layers 9 include, for example, a metal Ni as the main ingredient. The first internal electrode layers 8 and the second internal electrode layers 9 may include at least one selected from a metal, such as Cu, Ag, Pd, or Au, or an alloy including at least one of these metals, such as an Ag—Pd alloy, as the main ingredient or as an ingredient except the main ingredient. The first internal electrode layers 8 and the second internal electrode layers 9 may further include dielectric particles in the same composition system as that of the ceramic contained in the dielectric layers 7 as an ingredient except the main ingredient. Note that the metal as the main ingredient as used herein is a metal component with the highest percentage by mass.
The thickness of the first internal electrode layers 8 and the second internal electrode layers 9 is not specifically limited, but is preferably greater than or equal to about 0.4 μm and equal to or less than about 1.5 μm, for example. The total number of the first internal electrode layers 8 and the second internal electrode layers 9 is not specifically limited, but is preferably 200 or more, for example.
The external electrodes each include a base electrode, an inner plated layer, and an outer plated layer. The base electrode can be a sintered layer including a metal and glass. The metal includes Cu as the main ingredient. The metal may contain at least one selected from a metal, such as Ni, Ag, Pd, or Au, or an alloy, such as an Ag—Pd alloy, as the main ingredient or as an ingredient except the main ingredient. Examples of the glass include a glass component including at least one selected from B, Si, Ba, Mg, Al, Li, or any other material. Borosilicate glass can be used as a specific example of the glass. The inner plated layer can be made of at least one selected from a metal, such as Cu, Ni, Ag, Pd, or Au, or an alloy, such as an Ag—Pd alloy. The outer plated layer can be made of a metal, such as Sn.
The dimensions of the multilayer body 2 described above are not specifically limited. However, for example, the dimension from the first end surface LS1 to the second end surface LS2 of the multilayer ceramic capacitor 1 in the length direction L is preferably about 1.0 mm, the dimension from the first lateral surface WS1 to the second lateral surface WS2 of the multilayer ceramic capacitor 1 in the width direction W is preferably about 0.7 mm, and the dimension from the first main surface TS1 to the second main surface TS2 of the multilayer ceramic capacitor 1 in the lamination direction T is preferably about 0.5 mm, for example.
Examples of a measurement method for the lengths of the dielectric layers 7 and the internal electrode layers include a process in which a cross section of a multilayer body exposed by polishing is observed with a scanning electron microscope. Resultant values can be set to be the average of values obtained by measuring a plurality of portions corresponding to a region to be measured.
An example of a typical method for fabricating a multilayer ceramic capacitor 1 will be described. First, dielectric sheets for dielectric layers 7 and electrically conductive paste for first and second internal electrode layers 8 and 9 are prepared. The dielectric sheets and the electrically conductive paste include a binder and a solvent. A known material can be used as each of the binder and the solvent. Next, the electrically conductive paste is printed on a dielectric sheet in a pattern of a first internal electrode layer 8 or a second internal electrode layer 9 to form an internal electrode layer pattern on the dielectric sheet. Screen printing, gravure printing, or any other method can be used as a method for forming an internal electrode layer pattern. Next, a predetermined number of outer-layer dielectric sheets on each of which the internal electrode layer pattern has not been printed are stacked. Inner-layer dielectric sheets on each of which the internal electrode layer pattern has been printed are successively stacked on a stack of the outer-layer dielectric sheets. Meanwhile, dielectric paste for thickness correction may be appropriately applied to portions of the dielectric sheets corresponding to side gap portions as needed. A predetermined number of outer-layer dielectric sheets on each of which the internal electrode layer pattern has not been printed are stacked on the resultant stack. Thus, a multilayer sheet is produced.
Next, the multilayer sheet is pressed in the lamination direction by isostatic pressing, for example, to produce a multilayer block. Next, the multilayer block is cut into a predetermined size to obtain a multilayer chip. At this time, corners and ridges of the multilayer chip are rounded by barrel polishing or any other process. Next, the multilayer chip is fired to produce a multilayer body 2. Depending on the materials of the dielectric and the internal electrode layers, the firing temperature is preferably higher than or equal to about 900° C. and equal to or lower than about 1400° C., for example. Next, forming the external electrodes by a predetermined method can provide a multilayer ceramic capacitor 1.
While example embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-083016 | May 2022 | JP | national |
This application claims the benefit of priority to Japanese Patent Application No. 2022-083016 filed on May 20, 2022 and is a Continuation Application of PCT Application No. PCT/JP2023/015058 filed on Apr. 13, 2023. The entire contents of each application are hereby incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2023/015058 | Apr 2023 | WO |
| Child | 18758027 | US |
