Multilayer ceramic capacitor

Abstract

The application discloses a multilayer ceramic capacitor, which comprises a ceramic body and outer electrodes arranged at two ends of the ceramic body, wherein the outer electrodes at least comprise a base layer and a conductive layer; the base layer is arranged at the end surface of the ceramic body, and the conductive layer is arranged at the side surface of the base layer away from the ceramic body; the base layer and the conductive layer are both prepared by physical vapor deposition, so that the base layer and the conductive layer both have uniform thickness and regular outer contour, and the outer electrodes with regular shape are formed. The application can meet the requirement of embedded application of the multilayer ceramic capacitor, and the base layer and the conductive layer are concentratedly formed at the end surface of the ceramic body; during the film forming process, the position and direction of the film forming equipment do not need to be changed for covering the adjacent side edge area of the end surface of the ceramic body, which is beneficial to improving the film forming efficiency and simplifying the process.

Description

Technical Field

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

[0002] Multilayer ceramic capacitors (MLCCs) are common electronic components widely used in various electronic products and circuits, including consumer electronics, new energy, and communication equipment. With the increasing performance requirements of electronic devices, higher demands are being placed on the performance, size, and versatility of MLCCs. In particular, the rapid development of embedded packaging technology has led to an increasing number of embedded applications that embed MLCCs within circuit boards. These applications place stringent requirements on the shape and thickness uniformity of the external electrodes of the MLCCs. The external electrodes need to have a regular shape to ensure a proper fit between the MLCC and the substrate, thereby guaranteeing the reliability of the electrical connection after assembly.

[0003] In existing technologies, the external electrodes of multilayer ceramic capacitors are mostly fabricated by adhering conductive paste and then sintering it. For example, the multilayer ceramic capacitor disclosed in patent CN217902904U has its external electrodes obtained by adhering and sintering conductive paste such as copper paste. During the application and adhesion of the conductive paste, due to the influence of the paste's own gravity, the paste will form an irregular shape at the capacitor end, thicker in the middle and thinner at both sides. When nickel or tin layers are subsequently electroplated on the substrate, the plating layers will inherit the irregular contours of the substrate, resulting in external electrodes with uneven contours and thickness distributions. When this type of MLCC is used in embedded applications, the irregular external electrodes cannot achieve tight contact with the substrate, which can easily lead to loosening of the device after assembly, reducing the overall connection reliability of the device and making it difficult to meet the requirements of embedded packaging. Summary of the Invention

[0004] The purpose of this invention is to provide a multilayer ceramic capacitor to solve the problem that irregular outlines and thickness distributions of the outer electrodes affect the reliability of embedded packaging in the prior art.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] The present invention provides a multilayer ceramic capacitor, including a ceramic body and external electrodes disposed at both ends of the ceramic body. The external electrodes include at least a base layer and a conductive layer. The base layer is disposed on the end face of the ceramic body, and the conductive layer is disposed on the side of the base layer away from the ceramic body.

[0007] Both the base layer and the conductive layer are prepared by physical vapor deposition to ensure that both the base layer and the conductive layer have uniform thickness and regular outer contour, and form an outer electrode with a regular shape.

[0008] As a further improvement of one embodiment of the present invention, the cross-section of the external electrode along the stacking direction of the ceramic body is a rectangular structure.

[0009] And / or, the roughness of the end face of the ceramic body is greater than the roughness of the rest of the ceramic body surface;

[0010] And / or, the outer electrode further includes a protective layer and a welding layer, the protective layer at least covering the side of the conductive layer opposite to the base layer, and the welding layer at least covering the side of the protective layer opposite to the conductive layer;

[0011] Both the protective layer and the welding layer have a uniform thickness and a regular outer contour.

[0012] As a further improvement of one embodiment of the present invention, along the stacking direction of the ceramic body, the upper surface of the base layer and the upper surface of the conductive layer are both flush with the upper surface of the ceramic body, and the lower surface of the base layer and the lower surface of the conductive layer are both flush with the lower surface of the ceramic body; or, the upper surface and the lower surface of the base layer are respectively flush with the upper surface and the lower surface of the ceramic body, and the conductive layer covers the upper surface and the lower surface of the base layer.

[0013] The protective layer also covers the upper and lower surfaces of the base layer and / or the conductive layer, and the welding layer also covers the upper and lower surfaces of the protective layer.

[0014] As a further improvement of one embodiment of the present invention, the external electrode further includes conductive sheets. Along the stacking direction of the ceramic body, a pair of conductive sheets corresponding to the two end faces of the ceramic body are provided on the upper and lower surfaces of the ceramic body, and one end of each conductive sheet is flush with the corresponding end face of the ceramic body.

[0015] The base layer and / or the conductive layer are in contact with one end of the conductive sheet corresponding to the end face of the ceramic body, and the conductive sheet, the base layer and the conductive layer together serve as the conductive substrate of the external electrode;

[0016] The conductive sheet disposed on the upper surface of the ceramic body is the first conductive sheet, and the conductive sheet disposed on the lower surface of the ceramic body is the second conductive sheet.

[0017] As a further improvement of one embodiment of the present invention, the upper surface of the base layer and the upper surface of the conductive layer are both flush with the upper surface of the first conductive sheet, and the lower surface of the base layer and the lower surface of the conductive layer are both flush with the lower surface of the second conductive sheet.

[0018] The protective layer also covers the upper and lower surfaces of the base layer and the conductive layer, and also covers the upper surface of the first conductive sheet and the lower surface of the second conductive sheet. The welding layer also covers the upper and lower surfaces of the protective layer.

[0019] As a further improvement of one embodiment of the present invention, the conductive layer covers the exposed surface of the base layer, the protective layer covers the exposed surface of the conductive layer, and the upper surface of the protective layer is flush with the upper surface of the first conductive sheet, and the lower surface of the protective layer is flush with the lower surface of the second conductive sheet.

[0020] The welding layer also covers the upper and lower surfaces of the protective layer, and further covers the upper surface of the first conductive sheet and the lower surface of the second conductive sheet.

[0021] As a further improvement of one embodiment of the present invention, a ceramic layer is respectively provided on the upper and lower surfaces of the ceramic body. The ceramic layer is formed by printing ceramic paste and sintering it together with the ceramic body. The ceramic layer is disposed between the external electrodes at both ends. The surface of the ceramic layer away from the ceramic body is flush with the surface of the welding layer on the same side away from the ceramic body, so that the multilayer ceramic capacitor is formed into a regular cuboid structure.

[0022] As a further improvement of one embodiment of the present invention, along the stacking direction of the ceramic body, the upper and lower surfaces of the outer electrode are flush with the upper and lower surfaces of the ceramic body, respectively, so that the multilayer ceramic capacitor is formed into a regular cuboid structure.

[0023] As a further improvement of one embodiment of the present invention, along the stacking direction of the ceramic body, the upper surface of the base layer and the upper surface of the conductive layer are flush with each other and do not extend beyond the upper surface of the ceramic body, and the lower surface of the base layer and the lower surface of the conductive layer are flush with each other and do not extend beyond the lower surface of the ceramic body.

[0024] The protective layer also covers the upper and lower surfaces of the base layer and the conductive layer, and the welding layer also covers the upper and lower surfaces of the protective layer. The welding layer is flush with the upper surface of the ceramic body away from the upper surface of the protective layer and flush with the lower surface of the ceramic body away from the lower surface of the protective layer, so that the multilayer ceramic capacitor is formed into a regular cuboid structure.

[0025] As a further improvement of one embodiment of the present invention, the base layer is a titanium layer, a titanium alloy layer, or a chromium layer, and the base layer is formed only on the end face of the ceramic body by magnetron sputtering; the conductive layer is a copper layer, a silver layer, or an aluminum layer, and the conductive layer is formed only on the surface of the base layer by magnetron sputtering.

[0026] And / or, the protective layer is a nickel layer, and the solder layer is a tin layer;

[0027] And / or, the protective layer is formed by magnetron sputtering or electroplating, and the welding layer is formed by electroplating;

[0028] And / or, the thickness of the base layer is 70nm~100nm, and the thickness of the conductive layer is 2µm~5µm;

[0029] And / or, the thickness of the protective layer is 5µm to 8µm, and the thickness of the welding layer is 4µm to 7µm.

[0030] As a further improvement of one embodiment of the present invention, the conductive sheet is a nickel sheet, and the conductive sheet is formed by printing nickel paste and sintering it together with the ceramic body.

[0031] And / or, the thickness of the conductive sheet is 10µm~13µm.

[0032] Compared with the prior art, the beneficial effects of the present invention include at least the following: by forming a base layer and a conductive layer on the end face of a ceramic body through physical vapor deposition, the controllability of the film thickness and film formation area of ​​physical vapor deposition allows the base layer and conductive layer to have uniform thickness and regular outer contour, forming an external electrode with a regular shape. This avoids the problem in the prior art where the external electrode formed by the adhesion and sintering of conductive paste forms an irregular shape with a thick middle and thin sides at the end of the ceramic body due to the gravity of the conductive paste, and the subsequent electroplating layer inherits this irregular contour, thus meeting the needs of embedded applications of multilayer ceramic capacitors. At the same time, by concentrating the base layer and conductive layer on the end face of the ceramic body, the position and orientation of the film forming equipment do not need to be changed during the film forming process to cover the adjacent side areas of the end face of the ceramic body, which is beneficial to improving film forming efficiency and simplifying the process. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the multilayer ceramic capacitor in Embodiment 1 of the present invention;

[0034] Figure 2 This is a schematic diagram of the structure of the multilayer ceramic capacitor in Embodiment 2 of the present invention;

[0035] Figure 3 This is a schematic diagram of the structure of the multilayer ceramic capacitor in Embodiment 3 of the present invention;

[0036] Figure 4 This is a schematic diagram of the structure of the multilayer ceramic capacitor in Embodiment 4 of the present invention;

[0037] Figure 5 This is a schematic diagram of the structure of the multilayer ceramic capacitor in Embodiment 5 of the present invention;

[0038] Figure 6 This is a schematic diagram of the structure of the multilayer ceramic capacitor in Embodiment 6 of the present invention;

[0039] Figure 7 This is a schematic diagram of the structure of the multilayer ceramic capacitor in Embodiment 7 of the present invention;

[0040] Figure 8 This is a schematic diagram of the structure of the multilayer ceramic capacitor in Embodiment 8 of the present invention;

[0041] Figure 9 This is a schematic diagram of the structure of the multilayer ceramic capacitor in Embodiment 9 of the present invention;

[0042] Figure 10 This is a schematic diagram of the structure of the multilayer ceramic capacitor in Embodiment 10 of the present invention.

[0043] In the figure: 1. Ceramic body; 2. External electrode; 21. Base layer; 22. Conductive layer; 23. Protective layer; 24. Welding layer; 25. Conductive sheet; 251. First conductive sheet; 252. Second conductive sheet; 3. Ceramic layer. Detailed Implementation

[0044] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided to make the invention more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore repeated descriptions of them will be omitted.

[0045] The terms used to express position and direction in this invention are illustrated with reference to the accompanying drawings, but changes can be made as needed, and all such changes are included within the scope of protection of this invention.

[0046] See also Figures 1-10This invention provides a multilayer ceramic capacitor, comprising a ceramic body 1 and external electrodes 2 disposed at both ends of the ceramic body 1, i.e., external electrodes 2 are disposed on both end faces of the ceramic body 1. The ceramic body 1 comprises multiple stacked units, each stacked unit comprising a dielectric layer and an internal electrode disposed on the dielectric layer, wherein the internal electrodes of two adjacent stacked units are respectively connected to the external electrodes 2 located on different end faces of the ceramic body 1. The end faces of the ceramic body 1 are two side faces of the ceramic body 1 perpendicular to the stacking direction, and the stacking direction is the stacking direction of the dielectric layer and the internal electrodes within the ceramic body 1.

[0047] The external electrode 2 includes at least a base layer 21 and a conductive layer 22. The base layer 21 is disposed on the end face of the ceramic body 1, and the conductive layer 22 is disposed on the side of the base layer 21 facing away from the ceramic body 1. That is, in the direction from the end face of the ceramic body 1 outward, the base layer 21 is located between the end face of the ceramic body 1 and the conductive layer 22, the base layer 21 is in contact with the end face of the ceramic body 1, and the conductive layer 22 is in contact with the outer side of the base layer 21 (i.e., the side of the base layer 21 facing away from the ceramic body 1).

[0048] The base layer 21 is used to improve the bonding force between the outer electrode 2 and the end face of the ceramic body 1, and the conductive layer 22 is used to provide a conductive path. The base layer 21 contacts the corresponding exposed end of the inner electrode at the end face of the ceramic body 1. The conductive layer 22 forms a conductive structure connected to the corresponding inner electrode through contact with the base layer 21, enabling the inner electrode to be connected to an external circuit via the outer electrode 2. The layered structure between the base layer 21 and the conductive layer 22 also provides a basis for the continued deposition of other film layers on its outer side.

[0049] Specifically, both the base layer 21 and the conductive layer 22 are formed by physical vapor deposition (PVD) to ensure that both the base layer 21 and the conductive layer 22 have uniform thickness and regular outer contours, thus forming an external electrode 2 with a regular shape. For example, the base layer 21 and the conductive layer 22 can be deposited on the surface of the film to be formed by vacuum sputtering, vacuum evaporation, or vacuum ion plating. In the above different film formation methods, the base layer 21 is first formed on the end face of the ceramic body 1, and the conductive layer 22 is then formed on the outside of the base layer 21, maintaining the same interlayer arrangement. By controlling the deposition area and film thickness, a dense film layer attached to the end face of the ceramic body 1 is formed, so that the base layer 21 and the conductive layer 22 have uniform thickness and regular outer contours. In this way, the problem of irregular morphology with a thick middle and thin sides formed at the end of the ceramic body 1 due to the gravity of the conductive paste in the external electrode formed by the adhesion and sintering method in the prior art, as well as the problem of subsequent electroplating layers inheriting this irregular contour, can be avoided, thus meeting the needs of embedded applications of multilayer ceramic capacitors.

[0050] Simultaneously, during the preparation of the base layer 21 and the conductive layer 22, the area outside the end face of the ceramic body 1 is shielded, confining the deposition area to the end face of the ceramic body 1. That is, the base layer 21 and the conductive layer 22 are concentrated on the end face of the ceramic body 1. During the sequential formation of the base layer 21 and the conductive layer 22 on the same end face of the ceramic body 1, the position and sputtering direction of the equipment used for end face film formation can be maintained. There is no need to change the position and direction of the film formation equipment to cover adjacent side areas of the end face of the ceramic body 1 (such as the upper and lower surfaces of the ceramic body 1), which is beneficial for improving film formation efficiency and simplifying the process. It should be noted that the upper and lower surfaces of the ceramic body 1 are the two side surfaces of the ceramic body 1 along the stacking direction.

[0051] The base layer 21 can be a titanium layer, a titanium alloy layer, or a chromium layer. The base layer 21 is formed only on the end face of the ceramic body 1 by magnetron sputtering and does not extend to the upper or lower surfaces of the ceramic body 1. When forming the base layer 21, the base layer 21 is formed by magnetron sputtering in one direction along the stacking direction without changing the direction of the sputtering equipment. The conductive layer 22 can be a copper layer, a silver layer, or an aluminum layer. The conductive layer 22 is formed only on the surface of the base layer 21 by magnetron sputtering and does not extend to the upper or lower surfaces of the ceramic body 1. Specifically, the conductive layer 22 can be formed by magnetron sputtering in one direction along the stacking direction on the side of the base layer 21 without changing the direction of the sputtering equipment, or the conductive layer 22 can be formed by magnetron sputtering not only on the side of the base layer 21, but also on the upper and lower surfaces of the base layer 21. Since the thickness of the base layer 21 is relatively thin, the sputtering equipment can still sputter on the upper and lower surfaces of the base layer 21 in the same sputtering direction without changing the position and direction of the sputtering equipment.

[0052] Preferably, the base layer 21 is a titanium layer formed by magnetron sputtering, and the conductive layer 22 is a copper layer formed by magnetron sputtering. The titanium layer is bonded to the end face of the ceramic body 1, and the copper layer is formed on the surface of the titanium layer away from the ceramic body 1. The titanium layer mainly improves bonding, while the copper layer mainly provides conductivity. The conductive path of the copper layer is connected to the corresponding internal electrode, so that the bonding function and the conductivity function are respectively undertaken by the interconnected different film layers.

[0053] The thickness of the base layer 21 is 70nm~100nm to avoid the problem that the base layer 21 is too thin and cannot provide sufficient bonding force, which would lead to unreliable adhesion between the base layer 21 and the ceramic body 1. At the same time, it avoids the problem that the manufacturing cost and internal stress will increase due to the base layer 21 being too thick. Thus, while ensuring the bonding force between the base layer 21 and the ceramic body 1, both manufacturing cost and film reliability are taken into account.

[0054] The thickness of the conductive layer 22 is 2µm to 5µm to avoid the problem that the resistance of the conductive layer 22 is too high due to its thinness, which would affect the overall electrical performance of the multilayer ceramic capacitor. At the same time, it avoids the risk of the coating time being too long due to the conductive layer 22 being too thick, as well as the risk of increasing the internal stress of the film layer and causing the film layer to crack.

[0055] The present invention does not limit the specific values ​​of the thickness of the base layer 21 and the conductive layer 22 within the above-mentioned thickness range, and can adjust them according to actual product requirements and process conditions. For example, the thickness of the base layer 21 can be 70nm, 72nm, 75nm, 78nm, 80nm, 82nm, 85nm, 88nm, 90nm, 92nm, 95nm, 98nm or 100nm; the thickness of the conductive layer 22 can be 2µm, 2.2µm, 2.5µm, 2.8µm, 3µm, 3.2µm, 3.5µm, 3.8µm, 4µm, 4.2µm, 4.5µm, 4.8µm or 5µm.

[0056] Specifically, the cross-section of the outer electrode 2 along the stacking direction of the ceramic body 1 is a rectangular or nearly rectangular structure, which makes the sides of the outer electrode 2 flat and uniform in thickness, forming a regular outer contour. This facilitates a tight fit in the embedded installation position, helps ensure the reliability of the electrical connection after assembly, and meets the requirements of the regular shape of the outer electrode 2 for embedded applications of multilayer ceramic capacitors.

[0057] Of course, due to process errors, the angle between the outer side wall of the outer electrode 2 (i.e. the side of the outer electrode 2 facing away from the ceramic body 1) and the end face of the ceramic body 1 can be 0°~5°.

[0058] Specifically, the roughness of both end faces of the ceramic body 1 is greater than the roughness of the rest of the ceramic body 1. Before forming the base layer 21, the end faces of the ceramic body 1 are roughened, for example, by means of plasma spraying. The subsequent deposited base layer 21 combines with the roughened end faces, which helps to enhance the adhesion of the base layer 21 to the end faces of the ceramic body 1, thereby improving the bonding force between the external electrode 2 and the ceramic body 1.

[0059] Furthermore, the external electrode 2 also includes a protective layer 23 and a welding layer 24. The protective layer 23 at least covers the side of the conductive layer 22 facing away from the base layer 21, and the welding layer 24 at least covers the side of the protective layer 23 facing away from the conductive layer 22. Both the protective layer 23 and the welding layer 24 have uniform thickness and regular outer contours. Thus, the base layer 21, the conductive layer 22, the protective layer 23, and the welding layer 24 are sequentially formed at the end face of the ceramic body 1, with adjacent film layers in contact with each other. The protective layer 23 is placed between the conductive layer 22 and the welding layer 24, providing barrier protection for the conductive layer 22. The welding layer 24 is located on the outermost side, providing a surface for welding connection with external circuitry. Thus, the present invention provides a conductive substrate with uniform thickness and regular contour through the PVD-formed base layer 21 and conductive layer 22. The protective layer 23 and welding layer 24 are formed sequentially along the conductive substrate, and their thickness and outer contour are controlled accordingly. This can reduce the contour deviation caused by the irregular shape of the bottom layer being transferred to the outer layer layer by layer. The regular arrangement of each layer is conducive to the fit between the outer electrode 2 and the embedded installation position, thereby reducing the impact of assembly loosening on the reliability of electrical connection.

[0060] The protective layer 23 is a nickel layer, and the solder layer 24 is a tin layer. The nickel layer is in contact with the outer surface of the copper layer (i.e., the conductive layer 22) and is located between the copper layer and the tin layer, playing a role in covering and blocking protection; the tin layer covers the outer surface of the nickel layer, and the solderability of the tin layer forms an external solder joint.

[0061] Specifically, the protective layer 23 is formed by magnetron sputtering or electroplating, and the welding layer 24 is formed by electroplating.

[0062] The thickness of the protective layer 23 is 5µm to 8µm to avoid the problem that the protective layer 23 is too thin and cannot completely cover the conductive layer 22, resulting in insufficient blocking and protection effect of the protective layer 23. At the same time, it avoids the risk that the protective layer 23 will crack or even fall off if the protective layer 23 is too thick, as this will increase the internal stress of the film.

[0063] The thickness of the welding layer 24 is 4µm~7µm to avoid the welding layer 24 being too thin, resulting in insufficient weldable area and insufficient solder wetting during welding, which would cause insufficient welding strength and problems such as cold welding. At the same time, the welding layer 24 is not too thick, which would increase the overall size of the outer electrode 2 excessively, increase the accumulation of internal stress in the film layer, and cause the film layer to peel off. It would also cause material waste and increase production costs.

[0064] The present invention does not limit the specific values ​​of the protective layer 23 and the welding layer 24 within the above-mentioned thickness range, and can adjust them according to actual product requirements and process conditions. For example, the thickness of the protective layer 23 can be 5µm, 5.2µm, 5.5µm, 5.8µm, 6µm, 6.2µm, 6.5µm, 6.8µm, 7µm, 7.2µm, 7.5µm, 7.8µm or 8µm; the thickness of the welding layer 24 can be 4µm, 4.2µm, 4.5µm, 4.8µm, 5µm, 5.2µm, 5.5µm, 5.8µm, 6µm, 6.2µm, 6.5µm, 6.8µm or 7µm.

[0065] Example 1

[0066] like Figure 1 As shown, Embodiment 1 provides a multilayer ceramic capacitor, including a ceramic body 1 and external electrodes 2 disposed at both ends of the ceramic body 1. The external electrodes 2 include a base layer 21, a conductive layer 22, a protective layer 23 and a welding layer 24 sequentially formed on the end face of the ceramic body 1.

[0067] A base layer 21 is disposed on the end face of the ceramic body 1, and a conductive layer 22 is disposed on the side of the base layer 21 facing away from the ceramic body 1. Specifically, along the stacking direction of the ceramic body 1, the upper surface of the base layer 21 and the upper surface of the conductive layer 22 are flush with the upper surface of the ceramic body 1, and the lower surface of the base layer 21 and the lower surface of the conductive layer 22 are flush with the lower surface of the ceramic body 1. That is to say, the upper and lower boundaries of the base layer 21 and the conductive layer 22 reach the upper and lower edges of the end face of the ceramic body 1, respectively, and the height of the end face film layer is adapted to the height of the ceramic body 1.

[0068] Both the base layer 21 and the conductive layer 22 are prepared by physical vapor deposition to ensure that both the base layer 21 and the conductive layer 22 have uniform thickness and regular outer contour.

[0069] The base layer 21 can be a titanium layer, a titanium alloy layer, or a chromium layer, and the conductive layer 22 can be a copper layer, a silver layer, or an aluminum layer. In this embodiment, it is preferable to form a titanium layer on the end face of the ceramic body 1 and a copper layer on the side of the titanium layer away from the ceramic body 1 by magnetron sputtering.

[0070] The thickness of the base layer 21 is 70nm~100nm, and the thickness of the conductive layer 22 is 2µm~5µm. In this embodiment, the thickness of the base layer 21 is preferably 80nm, and the thickness of the conductive layer 22 is preferably 3µm.

[0071] The protective layer 23 covers the side of the conductive layer 22 away from the base layer 21, and the protective layer 23 also covers the upper and lower surfaces of the base layer 21 and the conductive layer 22 respectively. On the one hand, the protective layer 23 can provide all-round protection for the outer side of the conductive layer 22 (i.e., the side of the conductive layer 22 facing away from the base layer 21) as well as the upper and lower surfaces of the base layer 21 and the conductive layer 22, effectively isolating and blocking the internal conductive layer 22. This reduces the erosion of the base layer 21 and the conductive layer 22 by external moisture and corrosive media, thereby improving the corrosion resistance and overall service life of the film system. On the other hand, the protective layer 23 can be formed by magnetron sputtering or electroplating. Since the base layer 21 and the conductive layer 22 are relatively thin, multi-position film formation can be achieved without adjusting the equipment direction during the formation of the protective layer 23 by magnetron sputtering or electroplating. This eliminates the need for equipment repositioning and realignment, simplifies the processing flow, improves production efficiency, and avoids process errors caused by equipment reversal adjustments. This ensures that the protective layer 23 has a uniform film thickness and regular contour, providing a flat and stable film substrate for the subsequent outer welding layer 24.

[0072] The welding layer 24 covers the side of the protective layer 23 away from the conductive layer 22, and also covers the upper and lower surfaces of the protective layer 23. On the one hand, the covering structure of the welding layer 24 can provide a continuous and complete welding working surface for the multilayer ceramic capacitor, increase the weldable contact area, ensure sufficient solder wetting, and help improve the welding bond strength between the device and the external substrate, reducing the probability of poor soldering and desoldering. On the other hand, the covering structure of the welding layer 24 can form a secondary protection for the inner protective layer 23, reduce the intrusion of external moisture and impurities from the edge gaps, further protect the internal protective layer 23, conductive layer 22 and base layer 21, and delay the oxidation and corrosion of the film layer.

[0073] In this embodiment, the protective layer 23 is preferably formed by magnetron sputtering, and the welding layer 24 is preferably formed by electroplating.

[0074] The thickness of the protective layer 23 is 5µm to 8µm, and the thickness of the welding layer 24 is 4µm to 7µm. In this embodiment, the thickness of the protective layer 23 is preferably 6µm, and the thickness of the welding layer 24 is preferably 5µm.

[0075] In addition, based on the uniform thickness and regular shape of the base layer 21 and conductive layer 22 formed by physical vapor deposition, the protective layer 23 and welding layer 24 are formed in sequence on this basis, and their thickness and outer contour are controlled accordingly, so that the outer electrode 2 has a uniform thickness and regular shape, which can meet the requirements of device shape in embedded application scenarios, facilitate the tight assembly and bonding of the device with the substrate, and ensure the reliability of electrical connection after assembly.

[0076] Specifically, the cross-section of the outer electrode 2 along the stacking direction of the ceramic body 1 is a rectangular structure, that is, each side of the outer electrode 2 is flat and has a uniform thickness, forming a regular outer contour as a whole.

[0077] Specifically, the roughness of both ends of the ceramic body 1 is greater than the roughness of the rest of the ceramic body 1.

[0078] Example 2

[0079] like Figure 2 As shown, Embodiment 2 provides a multilayer ceramic capacitor. Unlike Embodiment 1, the upper and lower surfaces of the base layer 21 are flush with the upper and lower surfaces of the ceramic body 1, respectively. The conductive layer 22 covers the upper and lower surfaces of the base layer 21, and the protective layer 23 further covers the upper and lower surfaces of the conductive layer 22, forming a layered and regularly connected outer electrode 2 film structure.

[0080] Specifically, the base layer 21 is disposed on the end face of the ceramic body 1. In this embodiment, along the stacking direction of the ceramic body 1, the upper surface of the upper surface of the base layer 21 is flush with the upper surface of the ceramic body 1, and the lower surface of the base layer 21 is flush with the lower surface of the ceramic body 1. There are no high or low dislocations, no inward or outward structures between the end faces of the base layer 21 and the ceramic body 1, so that the upper and lower edges of the base layer 21 are perfectly connected with the contours of the upper and lower surfaces of the ceramic body 1, providing a regular structural reference for the subsequent extension and covering of the conductive layer 22.

[0081] The conductive layer 22 is disposed on the side of the base layer 21 facing away from the ceramic body 1. In this embodiment, based on the conductive layer 22 covering the side of the base layer 21 facing away from the ceramic body 1 in Embodiment 1, the upper end of the conductive layer 22 extends upward along the stacking direction and completely covers the upper surface of the base layer 21, while the lower end of the conductive layer 22 extends downward along the stacking direction and completely covers the lower surface of the base layer 21. This achieves comprehensive coverage and sealing of the side, upper surface, and lower surface of the base layer 21 facing away from the ceramic body 1. This completely isolates the base layer 21 from direct contact with the outside air, preventing problems such as oxidation and interface corrosion of the exposed base layer 21. Simultaneously, the large-area covering and bonding structure significantly increases the interface contact area between the conductive layer 22 and the base layer 21, ensuring sufficient and stable electrical connection between the two film layers and effectively reducing the contact resistance of the external electrode 2.

[0082] Based on the above structure, the protective layer 23 covers the side of the conductive layer 22 away from the base layer 21, and the protective layer 23 further covers the upper and lower surfaces of the conductive layer 22. The welding layer 24 covers the side of the protective layer 23 away from the conductive layer 22, and the welding layer 24 further covers the upper and lower surfaces of the protective layer 23.

[0083] Example 3

[0084] like Figure 3As shown, Embodiment 3 provides a multilayer ceramic capacitor. Unlike Embodiment 1, in this embodiment, the outer electrode 2 further includes a conductive sheet 25. Along the stacking direction of the ceramic body 1, a pair of conductive sheets 25 corresponding to the two end faces of the ceramic body 1 are provided on the upper and lower surfaces of the ceramic body 1, respectively. One end of each conductive sheet 25 is flush with the corresponding end face of the ceramic body 1.

[0085] In other words, the end of the conductive sheet 25 facing the end face of the ceramic body 1 is flush with the corresponding end face of the ceramic body 1. Starting from this flush end, the conductive sheet 25 extends into the interior of the ceramic body 1 in a direction parallel to the upper or lower surface of the ceramic body 1. At the same time, a pair of conductive sheets 25 located on the same surface of the ceramic body 1 are spaced apart from each other, so that the conductive sheets 25 belonging to the external electrodes 2 at both ends of the ceramic body 1 are separated from each other, ensuring that the external electrodes 2 at both ends of the ceramic body 1 are insulated from each other and avoiding short circuits.

[0086] The base layer 21 and / or conductive layer 22 are in contact with one end of the conductive sheet 25 corresponding to the end face of the ceramic body 1, and the conductive sheet 25, base layer 21, and conductive layer 22 together serve as the conductive substrate of the external electrode 2. Specifically, the base layer 21 can contact the end of the conductive sheet 25 adjacent to the end face of the ceramic body 1, and then the conductive layer 22 in contact with the base layer 21 can achieve electrical connection; alternatively, the conductive layer 22 can contact the end of the conductive sheet 25 adjacent to the end face of the ceramic body 1, or the base layer 21 and conductive layer 22 can respectively contact the end of the conductive sheet 25 adjacent to the end face of the ceramic body 1 in their respective contact areas. All of the above contact options ensure that the conductive sheet 25 is electrically connected to the base layer 21 and conductive layer 22, and together they serve as the conductive substrate of the external electrode 2. On the one hand, the conductive substrate, composed of conductive sheet 25, base layer 21 and conductive layer 22, expands the conductive area of ​​the external electrode 2 and improves the overall conductivity of the external electrode 2. At the same time, the conductive sheet 25 is connected to the base layer 21 and conductive layer 22, which can provide a continuous and complete film base for the subsequent protective layer 23 and welding layer 24, making it easier for the subsequent plating layer to be bonded across the end face of the ceramic body 1 and the upper and lower surfaces of the ceramic body 1. On the other hand, the interconnected conductive sheet 25, base layer 21 and conductive layer 22 can also form a structural support for the corner of the end face of the ceramic body 1, making it easier for the subsequent plating layer to cover the corner of the ceramic body 1, preventing water vapor and moisture from penetrating into the gaps at the corner of the ceramic body 1, and improving the moisture resistance of the device.

[0087] The conductive sheet 25 disposed on the upper surface of the ceramic body 1 is the first conductive sheet 251, and the conductive sheet 25 disposed on the lower surface of the ceramic body 1 is the second conductive sheet 252. That is, a pair of first conductive sheets 251 are disposed on the upper surface of the ceramic body 1, spaced apart and flush with their respective end faces of the ceramic body 1; a pair of second conductive sheets 252 are disposed on the lower surface of the ceramic body 1, spaced apart and flush with their respective end faces of the ceramic body 1; the first conductive sheets 251 and the second conductive sheets 252 are correspondingly disposed. The base layer 21 and / or the conductive layer 22 are in contact with one end of the first conductive sheet 251 and the second conductive sheet 252 corresponding to the end face of the ceramic body 1, and the first conductive sheet 251, the second conductive sheet 252, the base layer 21, and the conductive layer 22 together serve as the conductive substrate of the external electrode 2.

[0088] In this embodiment, the base layer 21 and the conductive sheet 25 are in contact with one end of the ceramic body 1. Specifically, along the stacking direction of the ceramic body 1, the upper surface of the base layer 21 and the upper surface of the conductive layer 22 are flush with the upper surface of the first conductive sheet 251, and the lower surface of the base layer 21 and the lower surface of the conductive layer 22 are flush with the lower surface of the second conductive sheet 252. Therefore, in this embodiment, the height of the base layer 21 and the conductive layer 22 along the stacking direction of the ceramic body 1 is equal to the total thickness of the ceramic body 1 and the conductive sheets 25 (i.e., the first conductive sheet 251 and the second conductive sheet 252) on its upper and lower surfaces along the stacking direction of the ceramic body 1. There are no steps between the PVD-formed base layer 21 and the conductive layer 22 at the end face of the ceramic body 1 and the conductive sheets 25 on the upper and lower surfaces of the ceramic body 1. The outer surface of the entire conductive substrate is flat and continuous, providing a film substrate with a regular shape for the subsequent protective layer 23 and welding layer 24. This is beneficial for the subsequent coating to obtain a uniform film thickness and a regular outer contour, which is suitable for the requirements of embedded packaging for device shape accuracy.

[0089] The protective layer 23 covers the side of the conductive layer 22 facing away from the base layer 21, and further covers the upper and lower surfaces of the base layer 21 and the conductive layer 22, as well as the upper surface of the first conductive sheet 251 and the lower surface of the second conductive sheet 252. The protective layer 23 can completely wrap the entire exposed area of ​​the conductive substrate (i.e., the base layer 21, the conductive layer 22, and the conductive sheet 25), and the protective layer 23 spans the corner area where the end face of the ceramic body 1 meets the upper and lower surfaces, completely encompassing the junction between the base layer 21 on the end face side of the ceramic body 1 and the first conductive sheet 251 and the second conductive sheet 252 within the coverage of the protective layer 23. In this way, the material of the outer welding layer 24 can be isolated to avoid unnecessary diffusion and erosion between the welding layer 24 and the internal conductive substrate; it can also provide all-round protection for the conductive sheet 25, the base layer 21, and the conductive layer 22, resisting the erosion of external air and corrosive media. Meanwhile, the protective layer 23 covers and seals the connection between the base layer 21 and the conductive sheet 25, reducing the dielectric channels exposed at the connection point and lowering the risk of moisture and humidity penetrating into the ceramic body 1 through gaps, thus improving the overall moisture resistance of the device. In addition, relying on the flat and stepless structure of the conductive substrate surface, the protective layer 23 forms a continuous and uniform film, making it less prone to local thinning or plating defects.

[0090] The solder layer 24 covers the side of the protective layer 23 away from the conductive layer 22, and further covers the upper and lower surfaces of the protective layer 23. The solder layer 24 completely covers all exposed surfaces of the protective layer 23, forming a continuous and flat soldering surface, increasing the effective soldering area, ensuring sufficient solder wetting, and improving the soldering bond strength between the device and the external substrate; at the same time, the solder layer 24 provides external sealing protection, further preventing the intrusion of moisture and impurities, and finally resulting in a multilayer ceramic capacitor with a regular overall shape.

[0091] In this embodiment, the conductive sheet 25 is a nickel sheet, and the protective layer 23 is a nickel layer. The conductive sheet 25 provides the electroplating base for the subsequent electroplating of the protective layer 23. The protective layer 23 is directly electroplated onto the outside of the nickel conductive sheet 25. Since both the protective layer 23 and the conductive sheet 25 are made of nickel, the compatibility between the same materials is better, which can effectively improve the interfacial bonding force between the protective layer 23 and the conductive sheet 25 and reduce the risk of plating peeling and flaking.

[0092] In this embodiment, the conductive sheet 25 is formed by printing nickel paste and sintering it together with the ceramic body 1. The sintering temperature of the nickel paste and the ceramic body are relatively close, usually 1100℃~1300℃. Therefore, the shrinkage of the nickel paste and the ceramic medium is matched, which can avoid problems such as delamination and cracking caused by shrinkage mismatch. Specifically, after the ceramic body 1 is laminated, nickel paste is printed on the upper and lower surfaces of the blank at the positions corresponding to the first conductive sheet 251 and the second conductive sheet 252. After printing, the ceramic body blank with nickel paste is subjected to isostatic pressing to obtain a dense block. The block is then sintered, and the nickel paste is solidified into a nickel conductive sheet 25 after sintering. This preparation method combines the forming process of the conductive sheet 25 with the sintering process of the ceramic body 1. The nickel conductive sheet 25 is sintered synchronously with the ceramic body 1 blank, eliminating the need for a separate secondary sintering process for the conductive sheet 25. This simplifies the process and effectively improves the overall production efficiency. Furthermore, the nickel slurry and the ceramic body 1 blank are co-fired and bonded during the high-temperature sintering process, resulting in a tight interface between the formed conductive sheet 25 and the ceramic body 1. This significantly improves the interfacial bonding force between the conductive sheet 25 and the ceramic body 1, reducing the risk of warping or detachment of the conductive sheet 25 and ensuring the structural stability of the conductive sheet 25 during subsequent sputtering, electroplating, and other coating processes, as well as during device service.

[0093] The thickness of the conductive sheet 25 is 10µm to 13µm. This invention does not limit the specific value of the conductive sheet 25 within the above-mentioned thickness range, and it can be adjusted according to actual product requirements and process conditions. The thickness of the conductive sheet 25 located on the upper surface of the ceramic body 1 and the thickness of the conductive sheet 25 located on the lower surface of the ceramic body 1 can be the same or different. For example, the thickness of the conductive sheet 25 can be 10µm, 10.2µm, 10.5µm, 10.8µm, 11µm, 11.2µm, 11.5µm, 11.8µm, 12µm, 12.2µm, 12.5µm, 12.8µm, or 13µm.

[0094] Example 4

[0095] like Figure 4 As shown, Embodiment 4 provides a multilayer ceramic capacitor. Unlike Embodiment 3, the conductive layer 22 covers the exposed surface of the base layer 21, and the protective layer 23 covers the exposed surface of the conductive layer 22. The upper surface of the protective layer 23 is flush with the upper surface of the first conductive sheet 251, and the lower surface of the protective layer 25 is flush with the lower surface of the second conductive sheet 252. The welding layer 24 also covers the upper and lower surfaces of the protective layer 23, as well as the upper surface of the first conductive sheet 251 and the lower surface of the second conductive sheet 252.

[0096] The base layer 21 and / or conductive layer 22 are in contact with one end of the conductive sheet 25 corresponding to the end face of the ceramic body 1, and the conductive sheet 25, the base layer 21, and the conductive layer 22 together serve as the conductive substrate of the external electrode 2. In this embodiment, the base layer 21 is disposed on the end face of the ceramic body 1, the conductive layer 22 is disposed on the side of the base layer 21 away from the ceramic body 1, and both the base layer 21 and the conductive layer 22 are connected to the conductive sheet 25.

[0097] Specifically, along the stacking direction of the ceramic body 1, the upper surface of the base layer 21 extends beyond the upper surface of the ceramic body 1 but does not extend beyond the upper surface of the first conductive sheet 251, and the lower surface of the base layer 21 extends beyond the lower surface of the ceramic body 1 but does not extend beyond the lower surface of the second conductive sheet 252. This restricts the base layer 21 as a whole within the end face range between the upper and lower conductive sheets 25 (i.e., the first conductive sheet 251 and the second conductive sheet 252), ensuring that the base layer 21 can form reliable contact with the corresponding conductive sheets 25 at the upper and lower edges, thereby achieving electrical connection.

[0098] The conductive layer 22 covers the exposed surfaces of the base layer 21, specifically the upper and lower surfaces of the base layer 21, as well as the side of the base layer 21 facing away from the ceramic body 1. The conductive layer 22 completely encapsulates the base layer 21, preventing it from being directly exposed to the external environment and thus avoiding oxidation failure, while simultaneously ensuring sufficient electrical conduction between the conductive layer 22 and the base layer 21. When covering the upper and lower surfaces of the base layer 21, the conductive layer 22 extends moderately upwards and downwards along the end face of the ceramic body 1 until it makes contact with the first conductive sheet 251 and the second conductive sheet 252, respectively, establishing a conductive path between the end film layer and the upper and lower conductive sheets 25. Furthermore, along the stacking direction of the ceramic body 1, the upper surface of the conductive layer 22 does not exceed the upper surface of the first conductive sheet 251, and the lower surface of the conductive layer 22 does not exceed the lower surface of the second conductive sheet 252. The upper and lower edges of the conductive layer 22 end within the height of the top surface of the corresponding conductive sheet 25. This configuration ensures reliable surface contact and conduction between the conductive layer 22 and the first conductive sheet 251 and the second conductive sheet 252, enabling the base layer 21, conductive layer 22, first conductive sheet 251, and second conductive sheet 252 to form an integrated conductive substrate, thereby increasing the conductive cross-sectional area of ​​the outer electrode 2 and reducing the impedance of the conductive circuit. It also enables direct connection between the conductive layer 22 and the conductive sheet 25, further ensuring the continuity and reliability of the conductive path of the entire conductive substrate.

[0099] The protective layer 23 covers the exposed surface of the conductive layer 22, with its upper surface flush with the upper surface of the first conductive sheet 251 and its lower surface flush with the lower surface of the second conductive sheet 252. Specifically, the protective layer 23 covers the upper and lower surfaces of the conductive layer 22, as well as the side of the conductive layer 22 facing away from the base layer 21, providing overall protection for the conductive layer 22. When covering the upper and lower surfaces of the base layer 21, the conductive layer 22 extends moderately upwards and downwards along the end face of the ceramic body 1 until it makes contact with the first conductive sheet 251 and the second conductive sheet 252, respectively. In other words, in addition to covering the entire exposed area of ​​the conductive layer 22, the protective layer 23 extends to both sides to the ends of the first conductive sheet 251 and the second conductive sheet 252 near the end face of the ceramic body 1. The upper surface of the protective layer 23 is flush with the upper surface of the first conductive sheet 251, and the lower surface of the protective layer 23 is flush with the lower surface of the second conductive sheet 252. That is, the thickness of the protective layer 23 along the stacking direction of the ceramic body 1 is equal to the total thickness of the ceramic body 1, the first conductive sheet 251, and the second conductive sheet 252 along the stacking direction of the ceramic body 1. In this way, the unevenness at the junction of the protective layer 23 with the first conductive sheet 251 and the second conductive sheet 252 can be eliminated, making the overall substrate surface continuous and flat. This provides a substrate with a good morphology for the subsequent film formation of the welding layer 24, and avoids defects such as thinning of the plating layer, incomplete plating, and stress concentration that are prone to occur at the step.

[0100] The welding layer 24 covers the side of the protective layer 23 away from the conductive layer 22, and further covers the upper and lower surfaces of the protective layer 23, as well as the upper surface of the first conductive sheet 251 and the lower surface of the second conductive sheet 252. The welding layer 24 can form an all-round outer sealing protection for the inner protective layer 23, conductive layer 22, base layer 21, and the first and second conductive sheets 251 and 252, completely sealing the tiny gaps at the joints of each film layer and the corners of the ceramic body 1, blocking the intrusion channels of water vapor, moisture, and corrosive media, avoiding oxidation, corrosion, and interlayer delamination of the internal conductive structure, and significantly improving the moisture resistance and long-term service stability of the device. In addition, as the outermost structure of the outer electrode 2, the welding layer 24 forms a large-area continuous welding working surface with a flat and complete covering surface, which allows the solder to be fully and evenly wetted and spread, effectively improving the welding strength between the device and the external circuit, eliminating welding defects such as cold solder joints and desoldering, and further ensuring the continuous stability of the conductive path during the operation of the multilayer ceramic capacitor.

[0101] Example 5

[0102] like Figure 5As shown, Embodiment 5 provides a multilayer ceramic capacitor. Unlike Embodiment 1, in this embodiment, the upper and lower surfaces of the ceramic body 1 are respectively provided with ceramic layers 3. The ceramic layers 3 are disposed between the external electrodes 2 at both ends, and the surface of the ceramic layers 3 away from the ceramic body 1 is flush with the surface of the welding layer 24 located on the same side away from the ceramic body 1, so that the multilayer ceramic capacitor is formed into a regular cuboid structure.

[0103] Specifically, the structure of the external electrode 2 in this embodiment continues the configuration of Embodiment 1. The external electrodes 2 at both ends of the ceramic body 1 are formed by stacking a base layer 21, a conductive layer 22, a protective layer 23, and a welding layer 24 sequentially on the end face of the ceramic body 1. The protective layer 23 covers the upper and lower surfaces of the base layer 21 and the conductive layer 22, respectively, and the welding layer 24 covers the upper and lower surfaces of the protective layer 23. The ceramic layer 3 is disposed on the upper and lower surfaces of the ceramic body 1 and is located between the welding layers 24 on the same side. The ceramic layer 3 is connected to the protective layer 23 and the welding layer 24 on the two end faces of the ceramic body 1 along the two end faces perpendicular to the stacking direction. That is, the side of the ceramic layer 3 near the external electrode 2 is adjacent to the inner edge of the protective layer 23 and the welding layer 24, the side of the ceramic layer 3 facing the ceramic body 1 is directly bonded to the ceramic body 1, and the surface of the ceramic layer 3 facing away from the ceramic body 1 and the surface of the welding layer 24 on the same side are on the same plane without any height difference.

[0104] Through this structural design, the ceramic layer 3 fills and compensates for the gaps on the upper and lower sides of the ceramic body 1 in Example 1, eliminating the stepped structure formed between the ceramic body 1 and the protective layers 23 and welding layers 24 at both ends, so that the overall outer contour of the device forms a regular and uniform cuboid shape. On the one hand, the regular cuboid shape can fully meet the assembly requirements of embedded packaging scenarios. The outer surfaces of the device are flat, and when embedded into the substrate, it can achieve complete fit with the substrate cavity, avoiding the problems of local suspension and assembly misalignment, and improving the structural stability after assembly. On the other hand, the ceramic layer 3 is a dielectric structure of the same material as the ceramic body 1, and the bonding reliability with the ceramic body 1 is high. There is no risk of peeling caused by heterogeneous interfaces. At the same time, the ceramic layer 3 fills the upper and lower sides of the ceramic body 1, which can play a role in structural reinforcement of the device as a whole, improving the device's resistance to bending and impact.

[0105] Specifically, ceramic layer 3 is formed by printing ceramic slurry and sintering it together with the ceramic body 1. After the ceramic body 1 is laminated, ceramic slurry is printed on the upper and lower surfaces of the body corresponding to the position of ceramic layer 3, so that the ceramic slurry printing area on the same side is located in the body substrate area between the external electrodes 2 at both ends of the ceramic body 1. After printing, the ceramic body 1 blank with ceramic slurry is subjected to isostatic pressing to make the ceramic slurry and the ceramic body 1 blank tightly bonded and form a dense block. The block is then sintered, and the ceramic slurry is solidified into ceramic layer 3 with the same material as the ceramic body 1.

[0106] Example 6

[0107] like Figure 6 As shown, Embodiment 6 provides a multilayer ceramic capacitor. Unlike Embodiment 2, in this embodiment, the upper and lower surfaces of the ceramic body 1 are respectively provided with ceramic layers 3. The ceramic layers 3 are disposed between the external electrodes 2 at both ends, and the surface of the ceramic layers 3 away from the ceramic body 1 is flush with the surface of the welding layer 24 located on the same side away from the ceramic body 1, so that the multilayer ceramic capacitor is formed into a regular cuboid structure.

[0108] Specifically, the structure of the external electrode 2 in this embodiment continues the configuration of embodiment 2. The external electrodes 2 at both ends of the ceramic body 1 are formed by stacking a base layer 21, a conductive layer 22, a protective layer 23, and a welding layer 24 sequentially on the end face of the ceramic body 1. The conductive layer 22 covers the upper and lower surfaces of the base layer 21, the protective layer 23 covers the upper and lower surfaces of each of the conductive layers 22, and the welding layer 24 covers the upper and lower surfaces of the protective layer 23. The conductive layer 22, the protective layer 23, and the welding layer 24 all protrude from the end face of the ceramic body 1. The ceramic layer 3 is disposed on the upper and lower surfaces of the ceramic body 1 and is located between the welding layers 24 on the same side. The ceramic layer 3 is connected to the conductive layer 22, the protective layer 23, and the welding layer 24 located on the two end faces of the ceramic body 1 along the two end faces perpendicular to the stacking direction. That is, the side of the ceramic layer 3 near the outer electrode 2 is adjacent to the inner edge of the conductive layer 22, the protective layer 23 and the welding layer 24. The side of the ceramic layer 3 facing the ceramic body 1 is directly attached to the ceramic body 1. The surface of the ceramic layer 3 facing away from the ceramic body 1 and the surface of the welding layer 24 on the same side are on the same plane, and there is no height difference.

[0109] With this structural design, the ceramic layer 3 fills and compensates for the missing positions on the upper and lower sides of the ceramic body 1 in Example 2, eliminating the stepped structure formed between the ceramic body 1 and the conductive layers 22, protective layer 23, and welding layer 24 at both ends, so that the overall outer contour of the device forms a regular and uniform cuboid shape.

[0110] Specifically, ceramic layer 3 is formed by printing ceramic slurry and sintering it together with the ceramic body 1. After the ceramic body 1 is laminated, ceramic slurry is printed on the upper and lower surfaces of the body corresponding to the position of ceramic layer 3, so that the ceramic slurry printing area on the same side is located in the body substrate area between the external electrodes 2 at both ends of the ceramic body 1. After printing, the ceramic body 1 blank with ceramic slurry is subjected to isostatic pressing to make the ceramic slurry and the ceramic body 1 blank tightly bonded and form a dense block. The block is then sintered, and the ceramic slurry is solidified into ceramic layer 3 with the same material as the ceramic body 1.

[0111] Example 7

[0112] like Figure 7 As shown, Embodiment 7 provides a multilayer ceramic capacitor. Unlike Embodiment 3, in this embodiment, the upper and lower surfaces of the ceramic body 1 are respectively provided with ceramic layers 3. The surface of the ceramic layer 3 facing away from the ceramic body 1 is flush with the surface of the welding layer 24 facing away from the ceramic body 1 on the same side, so that the multilayer ceramic capacitor is formed into a regular cuboid structure.

[0113] Specifically, the structure of the external electrode 2 in this embodiment continues the configuration of embodiment 2, and further provides a ceramic layer 3 on the upper and lower surfaces of the ceramic body 1. The ceramic layer 3 is arranged in the area between a pair of first conductive sheets 251 on the upper surface of the ceramic body 1 and in the area between a pair of second conductive sheets 252 on the lower surface of the ceramic body 1. The two end faces of the ceramic layer 3 perpendicular to the stacking direction are adjacent to the inner edges of the conductive sheet 25, the protective layer 23 and the welding layer 24 on the same side, respectively. The surface of the ceramic layer 3 facing the ceramic body 1 is tightly bonded to the ceramic body 1. The ceramic layer 3 does not invade the external electrode forming area where the conductive sheet 25, the base layer 21 and the conductive layer 22 are located. The surface of the ceramic layer 3 away from the ceramic body 1 is flush with the surface of the welding layer 24 on the same side away from the ceramic body 1. Thus, the ceramic layer 3 fills the gap between the two sets of conductive sheets 25 on the upper and lower surfaces of the ceramic body 1, and the surface of the ceramic layer 3 away from the ceramic body 1 and the surface of the welding layer 24 on the same side away from the ceramic body 1 are on the same plane, eliminating the recessed steps formed between the inner side of the conductive sheet 25 and the ceramic body 1 substrate. There are no obvious height differences on all the outer surfaces of the device, and the overall outline is a regular cuboid.

[0114] Specifically, ceramic layer 3 is formed by printing ceramic slurry and co-firing it with ceramic body 1. After the ceramic body 1 is laminated, ceramic slurry is printed on the upper and lower surfaces of the body corresponding to the position of ceramic layer 3, so that the ceramic slurry printing area on the same side is located in the body substrate area between the outer electrodes 2 at both ends of the ceramic body 1. After printing, the ceramic body 1 blank with ceramic slurry is subjected to isostatic pressing to make the ceramic slurry and the ceramic body 1 blank tightly bonded and form a dense block. The block is then sintered, and the ceramic slurry is solidified into ceramic layer 3 with the same material as ceramic body 1.

[0115] Example 8

[0116] like Figure 8 As shown, Embodiment 8 provides a multilayer ceramic capacitor. Unlike Embodiment 4, in this embodiment, the upper and lower surfaces of the ceramic body 1 are respectively provided with ceramic layers 3. The surface of the ceramic layer 3 facing away from the ceramic body 1 is flush with the surface of the welding layer 24 on the same side facing away from the ceramic body 1, so that the multilayer ceramic capacitor is formed into a regular cuboid structure.

[0117] Specifically, the structure of the external electrode 2 in this embodiment continues the arrangement of embodiment 3, and further provides a ceramic layer 3 on the upper and lower surfaces of the ceramic body 1. The ceramic layer 3 is arranged in the area between a pair of first conductive sheets 251 on the upper surface of the ceramic body 1 and in the area between a pair of second conductive sheets 252 on the lower surface of the ceramic body 1. The two end faces of the ceramic layer 3 perpendicular to the stacking direction are adjacent to the inner edges of the conductive sheet 25 and the welding layer 24 on the same side, respectively. The surface of the ceramic layer 3 facing the ceramic body 1 is tightly bonded to the ceramic body 1. The ceramic layer 3 does not invade the external electrode forming area where the conductive sheet 25, the base layer 21, and the conductive layer 22 are located. The surface of the ceramic layer 3 away from the ceramic body 1 is flush with the surface of the welding layer 24 on the same side away from the ceramic body 1. Thus, the ceramic layer 3 fills the gap between the two sets of conductive sheets 25 on the upper and lower surfaces of the ceramic body 1, and the surface of the ceramic layer 3 away from the ceramic body 1 and the surface of the welding layer 24 on the same side away from the ceramic body 1 are on the same plane, eliminating the recessed steps formed between the inner side of the conductive sheet 25 and the ceramic body 1 substrate. There are no obvious height differences on all the outer surfaces of the device, and the overall outline is a regular cuboid.

[0118] Specifically, ceramic layer 3 is formed by printing ceramic slurry and co-firing it with ceramic body 1. After the ceramic body 1 is laminated, ceramic slurry is printed on the upper and lower surfaces of the body corresponding to the position of ceramic layer 3, so that the ceramic slurry printing area on the same side is located in the body substrate area between the outer electrodes 2 at both ends of the ceramic body 1. After printing, the ceramic body 1 blank with ceramic slurry is subjected to isostatic pressing to make the ceramic slurry and the ceramic body 1 blank tightly bonded and form a dense block. The block is then sintered, and the ceramic slurry is solidified into ceramic layer 3 with the same material as ceramic body 1.

[0119] Example 9

[0120] like Figure 9 As shown, Embodiment 9 provides a multilayer ceramic capacitor. Unlike Embodiment 1, along the stacking direction of the ceramic body 1, the upper and lower surfaces of the outer electrode 2 are flush with the upper and lower surfaces of the ceramic body 1, respectively, so that the multilayer ceramic capacitor is formed into a regular cuboid structure.

[0121] In this embodiment, along the stacking direction of the ceramic body 1, the upper surface of the base layer 21 and the upper surface of the conductive layer 22 are flush with each other and do not extend beyond the upper surface of the ceramic body 1, and the lower surface of the base layer 21 and the lower surface of the conductive layer 22 are flush with each other and do not extend beyond the lower surface of the ceramic body 1. Specifically, the base layer 21 and the conductive layer 22 are sequentially formed on the end face of the ceramic body 1. The upper and lower surfaces of the base layer 21 and the conductive layer 22 have the same height and are controlled to shrink within the contour range of the upper and lower surfaces of the ceramic body 1, without protruding beyond the upper and lower surfaces of the ceramic body 1, effectively avoiding the formation of local steps and protrusions by the conductive film layer on the end face of the ceramic body 1.

[0122] The protective layer 23 covers the side of the conductive layer 22 away from the base layer 21, and further covers the upper and lower surfaces of the base layer 21 and the conductive layer 22 respectively, providing all-round sealing protection for the base layer 21 and the conductive layer 22. It can effectively isolate external moisture, air and corrosive media, prevent the base layer 21 and the conductive layer 22 from oxidation and corrosion failure, and inhibit the interdiffusion of elements in the subsequent metal plating layer, ensuring the structural and electrical stability of the conductive substrate.

[0123] The welding layer 24 covers the side of the protective layer 23 away from the conductive layer 22, and further covers the upper and lower surfaces of the protective layer 23. The upper surface of the welding layer 24 away from the protective layer 23 is flush with the upper surface of the ceramic body 1, and the lower surface of the welding layer 24 away from the protective layer 23 is flush with the lower surface of the ceramic body 1, so that the multilayer ceramic capacitor forms a regular cuboid structure. Through this structural matching design, the base layer 21, conductive layer 22, protective layer 23, and welding layer 24 at the end face of the ceramic body 1 are neatly covered layer by layer, and the height is adapted step by step. Finally, the upper and lower surfaces of the outermost welding layer 24 of the outer electrode 2 are kept at the same level as the upper and lower surfaces of the ceramic body 1, completely eliminating the high and low steps, protrusions and depressions at the junction of the device end face and the upper and lower surfaces.

[0124] Example 10

[0125] like Figure 10 As shown, Embodiment 10 provides a multilayer ceramic capacitor. Unlike Embodiment 2, along the stacking direction of the ceramic body 1, the upper and lower surfaces of the outer electrode 2 are flush with the upper and lower surfaces of the ceramic body 1, respectively, so that the multilayer ceramic capacitor is formed into a regular cuboid structure.

[0126] In this embodiment, the conductive layer 22 also covers the upper and lower surfaces of the base layer 21. Specifically, the base layer 21 and the conductive layer 22 are sequentially formed on the end face of the ceramic body 1. The conductive layer 22 is formed on the outer side of the base layer 21. The upper end of the conductive layer 22 extends upward along the stacking direction and completely covers the upper surface of the base layer 21. The lower end of the conductive layer 22 extends downward along the stacking direction and completely covers the lower surface of the base layer 21, thereby achieving all-round coverage and sealing of the sides, upper surfaces, and lower surfaces of the base layer 21 away from the ceramic body 1.

[0127] The protective layer 23 covers the side of the conductive layer 22 away from the base layer 21, and further covers the upper and lower surfaces of the conductive layer 22.

[0128] The welding layer 24 covers the side of the protective layer 23 away from the conductive layer 22, and further covers the upper and lower surfaces of the protective layer 23. The upper surface of the welding layer 24 away from the protective layer 23 is flush with the upper surface of the ceramic body 1, and the lower surface of the welding layer 24 away from the protective layer 23 is flush with the lower surface of the ceramic body 1, so that the multilayer ceramic capacitor forms a regular cuboid structure. Through this structural matching design, the base layer 21, conductive layer 22, protective layer 23, and welding layer 24 at the end face of the ceramic body 1 are neatly covered layer by layer, and the height is adapted step by step. Finally, the upper and lower surfaces of the outermost welding layer 24 of the outer electrode 2 are kept at the same level as the upper and lower surfaces of the ceramic body 1, completely eliminating the high and low steps, protrusions and depressions at the junction of the device end face and the upper and lower surfaces.

[0129] In summary, this invention provides a multilayer ceramic capacitor. A base layer 21 and a conductive layer 22 are formed on the end face of a ceramic body 1 by physical vapor deposition. By utilizing the controllability of the film thickness and film formation area of ​​physical vapor deposition, the base layer 21 and the conductive layer 22 have uniform thickness and regular outer contours, forming an outer electrode 2 with a regular shape. This avoids the problems of irregular morphology formed by the adhesion and sintering of conductive paste in the prior art, where the outer electrode 2 is thick in the middle and thin on both sides due to the gravity of the conductive paste at the end of the ceramic body 1, and the subsequent electroplating layer inheriting this irregular contour. This meets the requirements of embedded applications of multilayer ceramic capacitors. At the same time, by concentrating the base layer 21 and the conductive layer 22 on the end face of the ceramic body 1, the position and orientation of the film forming equipment do not need to be changed during the film forming process to cover the adjacent side areas of the end face of the ceramic body 1, which is beneficial to improve film forming efficiency and simplify the process.

[0130] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the invention without departing from the principles and spirit of the invention, and all such changes should fall within the protection scope of the claims of the present invention.

Claims

1. A multilayer ceramic capacitor, characterized in that, It includes a ceramic body and external electrodes disposed at both ends of the ceramic body. The external electrodes include at least a base layer and a conductive layer. The base layer is disposed on the end face of the ceramic body, and the conductive layer is disposed on the side of the base layer away from the ceramic body. Both the base layer and the conductive layer are prepared by physical vapor deposition to ensure that both the base layer and the conductive layer have uniform thickness and regular outer contour, and form an outer electrode with a regular shape.

2. The multilayer ceramic capacitor according to claim 1, characterized in that, The external electrode has a rectangular cross-section along the stacking direction of the ceramic body; And / or, the roughness of the end face of the ceramic body is greater than the roughness of the rest of the ceramic body surface; And / or, the outer electrode further includes a protective layer and a welding layer, the protective layer at least covering the side of the conductive layer opposite to the base layer, and the welding layer at least covering the side of the protective layer opposite to the conductive layer; Both the protective layer and the welding layer have a uniform thickness and a regular outer contour.

3. The multilayer ceramic capacitor according to claim 2, characterized in that, Along the stacking direction of the ceramic body, the upper surface of the base layer and the upper surface of the conductive layer are both flush with the upper surface of the ceramic body, and the lower surface of the base layer and the lower surface of the conductive layer are both flush with the lower surface of the ceramic body; or, the upper and lower surfaces of the base layer are respectively flush with the upper and lower surfaces of the ceramic body, and the conductive layer covers the upper and lower surfaces of the base layer. The protective layer also covers the upper and lower surfaces of the base layer and / or the conductive layer, and the welding layer also covers the upper and lower surfaces of the protective layer.

4. The multilayer ceramic capacitor according to claim 2, characterized in that, The external electrode also includes conductive sheets. Along the stacking direction of the ceramic body, a pair of conductive sheets corresponding to the two end faces of the ceramic body are provided on the upper and lower surfaces of the ceramic body, respectively. One end of each conductive sheet is flush with the corresponding end face of the ceramic body. The base layer and / or the conductive layer are in contact with one end of the conductive sheet corresponding to the end face of the ceramic body, and the conductive sheet, the base layer and the conductive layer together serve as the conductive substrate of the external electrode; The conductive sheet disposed on the upper surface of the ceramic body is the first conductive sheet, and the conductive sheet disposed on the lower surface of the ceramic body is the second conductive sheet.

5. The multilayer ceramic capacitor according to claim 4, characterized in that, The upper surface of the base layer and the upper surface of the conductive layer are both flush with the upper surface of the first conductive sheet, and the lower surface of the base layer and the lower surface of the conductive layer are both flush with the lower surface of the second conductive sheet. The protective layer also covers the upper and lower surfaces of the base layer and the conductive layer, and also covers the upper surface of the first conductive sheet and the lower surface of the second conductive sheet. The welding layer also covers the upper and lower surfaces of the protective layer.

6. The multilayer ceramic capacitor according to claim 4, characterized in that, The conductive layer covers the exposed surface of the base layer, the protective layer covers the exposed surface of the conductive layer, and the upper surface of the protective layer is flush with the upper surface of the first conductive sheet, and the lower surface of the protective layer is flush with the lower surface of the second conductive sheet. The welding layer also covers the upper and lower surfaces of the protective layer, and further covers the upper surface of the first conductive sheet and the lower surface of the second conductive sheet.

7. The multilayer ceramic capacitor according to any one of claims 3 to 6, characterized in that, The upper and lower surfaces of the ceramic body are respectively provided with ceramic layers. The ceramic layers are formed by printing ceramic paste and sintering together with the ceramic body. The ceramic layers are disposed between the external electrodes at both ends. The surface of the ceramic layer away from the ceramic body is flush with the surface of the welding layer on the same side away from the ceramic body, so that the multilayer ceramic capacitor is formed into a regular cuboid structure.

8. The multilayer ceramic capacitor according to claim 2, characterized in that, Along the stacking direction of the ceramic body, the upper and lower surfaces of the external electrode are flush with the upper and lower surfaces of the ceramic body, respectively, so that the multilayer ceramic capacitor is formed into a regular cuboid structure.

9. The multilayer ceramic capacitor according to claim 8, characterized in that, Along the stacking direction of the ceramic body, the upper surface of the base layer and the upper surface of the conductive layer are flush with each other and do not extend beyond the upper surface of the ceramic body, and the lower surface of the base layer and the lower surface of the conductive layer are flush with each other and do not extend beyond the lower surface of the ceramic body. The protective layer also covers the upper and lower surfaces of the base layer and the conductive layer, and the welding layer also covers the upper and lower surfaces of the protective layer. The welding layer is flush with the upper surface of the ceramic body away from the upper surface of the protective layer and flush with the lower surface of the ceramic body away from the lower surface of the protective layer, so that the multilayer ceramic capacitor is formed into a regular cuboid structure.

10. The multilayer ceramic capacitor according to claim 2, characterized in that, The base layer is a titanium layer, a titanium alloy layer, or a chromium layer, and the base layer is formed only on the end face of the ceramic body by magnetron sputtering. The conductive layer is a copper layer, a silver layer, or an aluminum layer, and the conductive layer is formed only on the surface of the base layer by magnetron sputtering. And / or, the protective layer is a nickel layer, and the solder layer is a tin layer; And / or, the protective layer is formed by magnetron sputtering or electroplating, and the welding layer is formed by electroplating; And / or, the thickness of the base layer is 70nm~100nm, and the thickness of the conductive layer is 2µm~5µm; And / or, the thickness of the protective layer is 5µm to 8µm, and the thickness of the welding layer is 4µm to 7µm.

11. The multilayer ceramic capacitor according to claim 4, characterized in that, The conductive sheet is a nickel sheet, and the conductive sheet is formed by printing nickel paste and sintering it together with the ceramic body; And / or, the thickness of the conductive sheet is 10µm~13µm.

Images