A multilayer ceramic capacitor

Abstract

This invention relates to the field of capacitor technology and discloses a multilayer ceramic capacitor, comprising a ceramic body and end electrodes disposed on both end faces of the ceramic body. The ceramic body further includes inner electrodes, a dielectric layer, and additional electrodes. The inner electrodes are arranged in parallel, with a dielectric layer disposed between adjacent inner electrodes. The additional electrodes are disposed at both ends of the side face of the ceramic body and are exposed on the side face of the ceramic body. The additional electrodes are connected to the end electrodes and are spaced apart from the inner electrodes. The additional electrodes are located between the ends of the inner electrodes and the ends of the end electrodes located on the side face of the ceramic body. The surface of the additional electrodes facing the inner electrodes is curved. This invention provides a multilayer ceramic capacitor with additional electrodes disposed between the ends of the end electrodes and the ends of the inner electrodes. The curved surface of the additional electrodes facing the inner electrodes eliminates charge concentration at the ends of the end electrodes and can significantly reduce electric field concentration.

Description

Technical Field

[0001] This invention relates to the field of capacitor technology, and in particular to a multilayer ceramic capacitor. Background Technology

[0002] Please refer to Figure 1 and Figure 2 This is a cross-sectional view of a prior art multilayer ceramic capacitor. End electrodes 2' are provided on both end faces 16' of the ceramic body 1', and the end electrodes 2' also extend to the upper surface 14', lower surface 15' and two side faces 17' of the ceramic body 1'. The ends of the end electrodes 2' extending to the upper and lower surfaces and side faces of the ceramic body are referred to as the ends of the end electrodes 2'. The ceramic body includes a plurality of dielectric layers 12' stacked along the thickness direction of the ceramic body and an inner electrode 11' disposed between two adjacent dielectric layers 12'. The end of the inner electrode 11' away from the end face connected to it is referred to as the end of the inner electrode 11'.

[0003] In the prior art, the end electrodes are formed by impregnating a ceramic body with electrode paste. The end electrodes extend to the ends of the upper and lower surfaces of the ceramic body. Due to the rheological changes of the electrode paste under the influence of gravity, sharp corners are formed at the ends. These sharp corners face the direction of the inner electrode and are obliquely aligned with the ends of the inner electrode. This leads to an increased concentration of the electric field at these points, posing a risk of breakdown and burnout to the multilayer ceramic capacitor. Summary of the Invention

[0004] The purpose of this invention is to provide a multilayer ceramic capacitor that can improve the problem of electric field concentration and reduce the risk of breakdown and burnout.

[0005] To achieve the above objectives, the present invention provides a multilayer ceramic capacitor, comprising a ceramic body and end electrodes disposed on both end faces of the ceramic body. The end electrodes extend to the upper surface, lower surface, and two side faces of the ceramic body, and the ends of the two end electrodes are disposed opposite each other with a distance between them. The ceramic body further comprises an inner electrode, a dielectric layer, and an additional electrode. The inner electrodes are disposed in parallel, and the dielectric layer is disposed between two adjacent inner electrodes. The additional electrode is disposed at both ends of the side face of the ceramic body and is exposed on the side face of the ceramic body. The additional electrode is connected to the end electrode and is distanced from the inner electrode. The additional electrode is located between the end of the inner electrode and the end of the end electrode located on the side face of the ceramic body. The surface of the additional electrode facing the inner electrode is curved.

[0006] Preferably, a recess is provided on the side of the ceramic body, and the additional electrode is disposed in the recess.

[0007] Preferably, the additional electrode also extends to the upper surface of the ceramic body.

[0008] Preferably, the additional electrode also extends to the lower surface of the ceramic body.

[0009] Preferably, the edge of the end of the inner electrode is provided as a rounded transition.

[0010] Preferably, the distance between the end of the additional electrode and the end face of the ceramic body adjacent to it is denoted as d1, and the distance between the end of the end electrode located on the side surface and the end face of the ceramic body corresponding to the end electrode is denoted as d2, where d1 > d2.

[0011] Preferably, the distance between the end of the internal electrode and the end face of the ceramic body that is not connected to it is denoted as d3, where d1 > d3.

[0012] Preferably, d1 is 10%-25% of the length of the multilayer ceramic capacitor.

[0013] Preferably, d3 is 5%-15% of the length of the multilayer ceramic capacitor.

[0014] Preferably, the distance between the additional electrode and the upper surface of the ceramic body is less than the distance between the inner electrode and the upper surface of the ceramic body.

[0015] This invention provides a multilayer ceramic capacitor, which has the following advantages compared with the prior art:

[0016] The multilayer ceramic capacitor of the present invention includes a ceramic body and end electrodes disposed on both end faces of the ceramic body. The end electrodes extend to the upper surface, lower surface, and two side surfaces of the ceramic body, and the ends of the two end electrodes are disposed opposite each other with a distance between them. The ceramic body also includes an inner electrode, a dielectric layer, and an additional electrode. The inner electrodes are arranged in parallel, and a dielectric layer is disposed between two adjacent inner electrodes. The additional electrode is disposed at both ends of the side surface of the ceramic body and is exposed on the side surface of the ceramic body. The additional electrode is connected to the end electrode and is separated from the inner electrode by a distance. The additional electrode is located between the end of the inner electrode and the end of the end electrode located on the side surface of the ceramic body, and the surface of the additional electrode facing the inner electrode is curved. With this structure, the additional electrode is disposed between the end of the end electrode and the end of the inner electrode, and the surface of the additional electrode facing the inner electrode is curved, eliminating charge concentration at the end of the end electrode and significantly reducing electric field concentration. Even if the area of ​​the inner electrode is increased to obtain high capacitance, thus reducing the distance between the end of the inner electrode and the end of the end electrode, the multilayer ceramic capacitor can still maintain good voltage withstand performance. Attached Figure Description

[0017] Figure 1 This is a side cross-sectional view of a multilayer ceramic capacitor in the prior art.

[0018] Figure 2This is a top cross-sectional view of a multilayer ceramic capacitor in the prior art.

[0019] Figure 3 This is a structural schematic diagram of an embodiment of the present invention.

[0020] Figure 4 This is a side sectional view of Embodiment 1 of the present invention.

[0021] Figure 5 This is a top sectional view of Embodiment 1 of the present invention.

[0022] Figure 6 This is a top sectional view of Embodiment 2 of the present invention.

[0023] Figure 7 This is a top sectional view of Embodiment 3 of the present invention.

[0024] In the figure, 1 is the ceramic body; 2 is the end electrode; 11 is the inner electrode; 12 is the dielectric layer; 13 is the auxiliary electrode; 14 is the upper surface of the ceramic body; 15 is the lower surface of the ceramic body; 16 is the end face of the ceramic body; and 17 is the side face of the ceramic body. Detailed Implementation

[0025] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0026] In the description of this invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0028] Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0029] Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0030] Example 1

[0031] Please refer to Figures 3-5 A preferred embodiment of the present invention provides a multilayer ceramic capacitor, comprising a ceramic body 1 and end electrodes 2 disposed on two end faces 16 of the ceramic body 1. The end electrodes 2 extend to the upper surface 14, lower surface 15, and two side faces 17 of the ceramic body 1, with the ends of the two end electrodes 2 positioned opposite each other and spaced apart. The ceramic body 1 also includes inner electrodes 11, a dielectric layer 12, and additional electrodes 13. The inner electrodes 11 are arranged in parallel, with a dielectric layer 12 disposed between adjacent inner electrodes 11. The additional electrodes 13 are disposed at both ends of the side faces 17 of the ceramic body 1 and are exposed on the side faces 17. The additional electrodes 13 are connected to the end electrodes 2 and spaced apart from the inner electrodes 11. The additional electrodes 13 are located between the ends of the inner electrodes 11 and the ends of the end electrodes 2 located on the side faces 17 of the ceramic body 1. The surface of the additional electrodes 13 facing the inner electrodes 11 is curved. The shape of the curved surface is not specifically limited, as long as it is smooth and avoids sharp corners. In this embodiment, the curved surface is parabolic in shape on the profile of the lateral cross section. In other embodiments, other shapes may also be provided.

[0032] The length of multilayer ceramic capacitors ranges from 0.6mm to 1.6mm, the width ranges from 0.3mm to 0.8mm, and the thickness ranges from 0.3mm to 0.8mm.

[0033] The multilayer ceramic capacitor of this invention has a structure in which an additional electrode 13 is provided between the end of the terminal electrode 2 and the end of the inner electrode 11. The surface of the additional electrode 13 facing the inner electrode 11 is curved, which eliminates the charge concentration at the end of the terminal electrode 2 and can significantly reduce the electric field concentration. Even if the area of ​​the inner electrode 11 is increased to obtain a high capacitance, thereby reducing the distance between the end of the inner electrode 11 and the end of the terminal electrode 2, the multilayer ceramic capacitor can still have good voltage withstand performance.

[0034] The number of internal electrodes 11 is preferably 20 or more. To achieve a large volume utilization rate and facilitate production, the internal electrodes 11 are preferably rectangular thin layers. The thickness of the internal electrodes 11 is preferably 1μm-3μm. In addition, to prevent moisture and mechanical damage, the internal electrodes 11 are spaced at a certain distance from the upper surface 14, lower surface 15 and two side surfaces 17 of the ceramic body 1.

[0035] There are four auxiliary electrodes 13, which are respectively disposed at the four corners of the ceramic body 1. The auxiliary electrodes 13 are laterally disposed on the side 17 of the ceramic body 1 and are columnar.

[0036] In this embodiment, the inner electrode 11 and the auxiliary electrode 13 are made of the same material, such as nickel or copper, to facilitate co-firing.

[0037] The material of the terminal electrode 2 is copper, with a thickness of 20μm-60μm. If the thickness is less than 20μm, it is difficult to prepare the terminal electrode 2 by impregnation. If the thickness is greater than 60μm, it will lead to an excessive increase in the thickness of the multilayer ceramic capacitor 200.

[0038] In this embodiment, a recess is provided on the side 17 of the ceramic body 1, and the additional electrode 13 is disposed in the recess. This arrangement prevents the additional electrode 13 from occupying too much space on the surface of the ceramic body 1, thus avoiding an excessively large size for the multilayer ceramic capacitor.

[0039] In this embodiment, the auxiliary electrode 13 does not extend to the upper surface 14 and lower surface 15 of the ceramic body 1. In other embodiments, the auxiliary electrode 13 also extends to the upper surface 14 of the ceramic body 1 and to the lower surface 15 of the ceramic body 1.

[0040] In this embodiment, the distance between the end of the auxiliary electrode 13 and the end face 16 of the ceramic body 1 adjacent to it is denoted as d1, and the distance between the end of the end electrode 2 located on the side 17 and the end face 16 of the ceramic body 1 corresponding to the end electrode 2 is denoted as d2, where d1 > d2. This arrangement can eliminate charge concentration at the end of the end electrode 2. The distance between the end of the inner electrode 11 and the end face 16 of the ceramic body 1 not connected to it is denoted as d3, where d1 > d3. This causes the ends of the inner electrode 11 and the ends of the auxiliary electrode 13 to be staggered along the length of the multilayer ceramic capacitor, thereby reducing the degree of electric field concentration and facilitating the acquisition of a higher capacitance.

[0041] d1 is 10%-25% of the length of the multilayer ceramic capacitor. If d1 is less than 10% of the length of the multilayer ceramic capacitor, it is not convenient to solder the multilayer ceramic capacitor. If d1 is greater than 25% of the length of the multilayer ceramic capacitor, the multilayer ceramic capacitor soldered onto the circuit board is prone to breakage due to greater mechanical stress.

[0042] d3 is 5%-15% of the length of the multilayer ceramic capacitor. If d3 is less than 5% of the length of the multilayer ceramic capacitor, the process allowance is insufficient, which may easily lead to a short circuit between the internal electrode 11 and the unconnected terminal electrode 2. If d3 is greater than 15% of the length of the multilayer ceramic capacitor, it is difficult to obtain a high capacitance.

[0043] The edge of the inner electrode 11 is rounded to reduce the charge concentration of the inner electrode 11 and further improve the voltage withstand performance of the multilayer ceramic capacitor.

[0044] The distance between the auxiliary electrode 13 and the upper surface 14 of the ceramic body 1 is less than the distance between the inner electrode 11 and the upper surface 14 of the ceramic body 1. Similarly, the distance between the auxiliary electrode 13 and the lower surface 15 of the ceramic body 1 is less than the distance between the inner electrode 11 and the lower surface 15 of the ceramic body 1. With this structure, a more sufficient effect of reducing electric field concentration is achieved.

[0045] This embodiment also provides a method for preparing a multilayer ceramic capacitor, including the following steps:

[0046] Step 1: Prepare a ceramic membrane using ceramic slurry as raw material.

[0047] Ceramic powder, binder, and organic solvent are mixed and dispersed evenly using ball milling or sand milling to obtain ceramic slurry, which is then cast into a ceramic film.

[0048] Ceramic powder can be a commonly used ceramic material in multilayer ceramic capacitors, such as barium titanate, calcium zirconate, and calcium titanate.

[0049] Step 2: Stack multiple ceramic films to form a bottom ceramic cover. Print metal paste and ceramic paste on the bottom ceramic cover in a certain order to obtain the inner electrode 11 pattern, the additional electrode 13 pattern and the dielectric layer 12. Then stack multiple ceramic films to form a top ceramic cover to obtain a ceramic substrate.

[0050] Multiple ceramic films obtained in step one are stacked to form a bottom ceramic cover of a certain thickness. The bottom surface of the bottom ceramic cover corresponds to the lower surface 15 of the ceramic body 1, and the thickness of the bottom ceramic cover corresponds to the distance from the auxiliary electrode 13 to the lower surface 15. Metal paste and ceramic paste are printed on the bottom ceramic cover in a certain order using a screen printing machine. In this embodiment, metal paste is first printed on the bottom ceramic cover and dried to form the pattern of the auxiliary electrode 13. Then, ceramic paste is printed and dried to form a ceramic layer. The ceramic layer completely covers the area outside the pattern of the auxiliary electrode 13 but does not overlap with the pattern of the auxiliary electrode 13. The metal paste and ceramic paste are printed and dried alternately until the pattern of the auxiliary electrode 13 and the ceramic layer of the required thickness are obtained. Then, metal paste is printed on the ceramic layer and dried to form the pattern of the inner electrode 11. The pattern of the inner electrode 11 is spaced a certain distance from the pattern of the auxiliary electrode 13. Then, ceramic paste is printed on the pattern of the inner electrode 11 and dried to form a ceramic layer. The ceramic layer completely covers the pattern of the inner electrode 11 but does not cover the pattern of the auxiliary electrode 13. After this, there is no particular limitation on the order in which the inner electrode 11 pattern, the additional electrode 13 pattern, and the ceramic layer are formed, as long as the adjacent inner electrode 11 patterns are separated by the ceramic layer and the additional electrode 13 patterns are connected vertically to form a columnar structure.

[0051] Alternatively, the ceramic paste obtained in step one of screen printing can be used to form the bottom ceramic cover and the top ceramic cover.

[0052] Preferably, the inner electrode 11 pattern is reciprocated in the direction corresponding to the length of the multilayer ceramic capacitor, so that the inner electrode 11 pattern is divided into two sets of patterns respectively corresponding to the inner electrode 11, which facilitates obtaining high capacitance. After all the inner electrode 11 patterns are formed, a ceramic layer and an additional electrode 13 pattern can be formed over it, such that the distance from the additional electrode 13 to the upper surface 14 is less than the distance from the inner electrode 11 to the upper surface 14, and the distance from the additional electrode 13 to the lower surface 15 is less than the distance from the inner electrode 11 to the lower surface 15. Finally, multiple ceramic film layers obtained in step one are stacked on the ceramic layer and the additional electrode 13 pattern to form a top ceramic cover of a certain thickness, resulting in a ceramic substrate. The top surface of the top ceramic cover corresponds to the upper surface 14 of the ceramic body 1, and the thickness of the top ceramic cover corresponds to the shortest distance from the additional electrode 13 to the upper surface 14.

[0053] The metal in the metal paste is preferably nickel or copper. Preferably, the same metal paste is used to form the inner electrode 11 pattern and the additional electrode 13 pattern to maintain consistent sintering characteristics, facilitate co-firing, and ensure good density of the ceramic body 1.

[0054] Step 3: Cut the ceramic substrate to obtain multiple ceramic green sheets.

[0055] The ceramic substrate is cut longitudinally and transversely according to the required length and width dimensions to obtain multiple rectangular ceramic green sheets, with the edges of the inner electrode 11 and the auxiliary electrode 13 exposed on the cut surfaces. Specifically, on each ceramic green sheet, the inner electrode 11 is exposed on two cut surfaces corresponding to the two end faces 16 of the ceramic body 1, and the auxiliary electrode 13 is exposed on four cut surfaces corresponding to the two end faces 16 and the two side faces 17 of the ceramic body 1.

[0056] Step 4: Sinter the ceramic green sheet to obtain ceramic body 1.

[0057] The ceramic green sheet is heated to 950℃-1300℃ and sintered to obtain ceramic body 1. After sintering, the pattern of the inner electrode 11 becomes the inner electrode 11, the pattern of the auxiliary electrode 13 becomes the auxiliary electrode 13, and the ceramic layer becomes the dielectric layer 12.

[0058] If necessary, the ceramic green sheets can be heat-treated before sintering to remove organic components and improve the mechanical and dielectric properties of the ceramic body 1.

[0059] Step 5: Impregnate both ends of the ceramic body 1 with copper paste, and then sinter the copper paste to form the terminal electrodes 2, thereby obtaining the multilayer ceramic capacitor of the present invention.

[0060] The two ends of the ceramic body 1 are impregnated with copper paste, and then the copper paste is heated to 950℃-1300℃ for sintering. After sintering, the copper paste forms two terminal electrodes 2, thus obtaining a multilayer ceramic capacitor. By controlling the impregnation depth of the copper paste, d2 < d1 is made.

[0061] If necessary, after the sintering process in step four, the ceramic body 1 can be tumble ground to round the edges and corners of the ceramic body 1 and prevent mechanical damage.

[0062] Example 2

[0063] The multilayer ceramic capacitor provided in Example 2 differs from that in Example 1 in that, please refer to... Figure 6 The end of the auxiliary electrode 13 is semi-circular in the downward cross section, and the connection between one end of the auxiliary electrode 13 and the end electrode 2 is located at the end face 16 of the ceramic body 1.

[0064] Example 3

[0065] The multilayer ceramic capacitor provided in Example 3 differs from that in Example 1 in that, please refer to... Figure 7 The auxiliary electrode 13 is not connected to either end face 16, and both ends of the auxiliary electrode 13 are arc-shaped.

[0066] In summary, the present invention provides a multilayer ceramic capacitor in which an additional electrode 13 is provided between the end of the terminal electrode 2 and the end of the inner electrode 11. The surface of the additional electrode 13 facing the inner electrode 11 is curved, which eliminates the charge concentration at the end of the terminal electrode 2 and can significantly reduce the electric field concentration. Even if the area of ​​the inner electrode 11 is increased to obtain a high capacitance, thereby reducing the distance between the end of the inner electrode 11 and the end of the terminal electrode 2, the multilayer ceramic capacitor can still have good voltage withstand performance.

[0067] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A multilayer ceramic capacitor, characterized in that, The device includes a ceramic body and end electrodes disposed on both ends of the ceramic body. The end electrodes extend to the upper surface, lower surface, and two side surfaces of the ceramic body, and the ends of the two end electrodes are disposed opposite each other with a distance between them. The ceramic body also includes an inner electrode, a dielectric layer, and an additional electrode. The inner electrodes are disposed in parallel and the dielectric layer is disposed between two adjacent inner electrodes. The additional electrode is disposed at both ends of the side surface of the ceramic body and is exposed on the side surface of the ceramic body. The additional electrode is connected to the end electrode and is separated from the inner electrode by a distance. The additional electrode is located between the end of the inner electrode and the end of the end electrode located on the side surface of the ceramic body. The surface of the additional electrode facing the inner electrode is curved. The distance between the auxiliary electrode and the upper surface of the ceramic body is less than the distance between the inner electrode and the upper surface of the ceramic body; A recess is provided on the side of the ceramic body, and the additional electrode is disposed in the recess; The distance between the end of the additional electrode and the end face of the ceramic body adjacent to it is denoted as d1, and the distance between the end of the end electrode located on the side surface and the end face of the ceramic body corresponding to the end electrode is denoted as d2, where d1 > d2; d1 is 10%-25% of the length of the multilayer ceramic capacitor.

2. The multilayer ceramic capacitor according to claim 1, characterized in that, The additional electrode also extends to the upper surface of the ceramic body.

3. The multilayer ceramic capacitor according to claim 1, characterized in that, The additional electrode also extends to the lower surface of the ceramic body.

4. The multilayer ceramic capacitor according to claim 1, characterized in that, The edge of the end of the inner electrode is set as a rounded transition.

5. The multilayer ceramic capacitor according to claim 1, characterized in that, The distance between the end of the internal electrode and the end face of the ceramic body that is not connected to it is denoted as d3, where d1 > d3.

6. The multilayer ceramic capacitor according to claim 5, characterized in that, d3 is 5%-15% of the length of the multilayer ceramic capacitor.

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