Multilayer ceramic capacitor and method of manufacturing the same

Abstract

The application relates to the technical field of capacitors, and discloses a multilayer ceramic capacitor and a preparation method thereof. The multilayer ceramic capacitor comprises a ceramic body and two end electrodes arranged on two end surfaces of the ceramic body respectively, the end electrodes extend to the outer circumferential surface of the ceramic body, the ends of the two end electrodes are arranged oppositely and have a distance therebetween, an insulating layer is arranged on the end electrodes, a conductive layer is coated on the insulating layer, the conductive layer covers the insulating layer and extends to the end electrodes, and the end portions of the end electrodes are exposed to the conductive layer. The application can realize automatic electrical performance sorting, the connection area of the multilayer ceramic capacitor and the circuit board is small, the distance between the two welding points is small, the piezoelectric vibration of the multilayer ceramic capacitor is effectively inhibited from being transmitted to the circuit board, the ringing noise of the circuit board is reduced, the plating solution penetration path is long, the plating solution cannot reach the inner electrode, and the insulation resistance is not reduced.

Description

Technical Field

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

[0002] Currently, multilayer ceramic capacitors with base metal electrodes typically have a three-layer structure of copper, nickel, and tin as their terminal electrodes. A copper layer is formed on the ceramic body using a sintering process, followed by electroplating to form nickel and tin layers. The copper layer is generally formed by sintering copper paste in a neutral atmosphere. However, the organic components in the copper paste are difficult to remove completely in a low-oxygen-pressure atmosphere, resulting in poor density of the copper layer. During electroplating, the plating solution penetrates through a very thin copper layer (e.g., 5μm-60μm) and further seeps into the ceramic body through the gaps between the inner electrode and the ceramic body. This causes a decrease in the insulation resistance of the multilayer ceramic capacitor, and in severe cases, short circuits. To prevent plating solution from penetrating the copper layer, the industry uses an insulating layer to block the plating solution. However, because the insulating layer is non-conductive, automated electrical performance sorting of multilayer ceramic capacitors is not possible, making large-scale production difficult.

[0003] In addition, barium titanate-based ceramics are widely used as dielectric materials for high-capacitance multilayer ceramic capacitors. However, due to the reverse piezoelectric effect of barium titanate-based ceramics, there is a problem of circuit board noise. That is, when an AC voltage is applied to the multilayer ceramic capacitor, the multilayer ceramic capacitor will expand and contract, and this vibration will be transmitted to the circuit board through the solder joints, causing the circuit board to vibrate and produce a buzzing sound. The higher the capacitance of the multilayer ceramic capacitor, the more severe the circuit board noise. Summary of the Invention

[0004] The purpose of this invention is to provide a multilayer ceramic capacitor and its preparation method that can perform automated electrical performance sorting, have a long plating solution penetration path to prevent the plating solution from reaching the inner electrode without causing a decrease in insulation resistance, and effectively suppress the transmission of piezoelectric vibration to the circuit board, thereby reducing the noise of the circuit board.

[0005] To achieve the above objectives, the present invention provides a multilayer ceramic capacitor, comprising a ceramic body and two end electrodes respectively disposed on two end faces of the ceramic body. The end electrodes extend to the outer peripheral side surface of the ceramic body, and the ends of the two end electrodes are disposed opposite each other with a distance between them. An insulating layer is provided on the end electrodes, and a conductive layer is covered on the insulating layer. The conductive layer covers the insulating layer and extends to the end electrodes, and the end of the end electrodes is exposed outside the conductive layer.

[0006] In a preferred embodiment of the present invention, the end electrode includes a connecting electrode and a welding electrode. The connecting electrode covers the end face of the ceramic body and extends to the outer peripheral side surface of the ceramic body. The welding electrode is circumferentially disposed on the outer peripheral side surface and connected to the end face of the connecting electrode. The connecting electrode is a single-layer electrode, and the welding electrode is a composite-layer electrode. The insulating layer covers the connecting electrode, and the conductive layer completely covers the insulating layer and extends to the welding electrode.

[0007] In a preferred embodiment of the present invention, the connecting electrode is a copper electrode; the welding electrode includes a bottom electrode, a middle electrode and a top electrode arranged sequentially from the inside out, wherein the bottom electrode is a copper electrode layer, the middle electrode is a nickel electrode layer, and the top electrode is a tin electrode layer; the material of the conductive layer is any one of copper, nickel, copper-nickel alloy, nickel-chromium alloy, nickel-vanadium alloy, titanium-tungsten alloy and indium-gallium alloy.

[0008] In a preferred embodiment of the present invention, the distance between the end face of the welding electrode and the end face of the ceramic body adjacent to it is denoted as d1; the distance between the end face of the connecting electrode and the end face of the ceramic body adjacent to it is denoted as d2, and the distance between the end face of the connecting electrode and the end face of the ceramic body adjacent to it is equal to the distance between the end face of the insulating layer and the end face of the ceramic body adjacent to it; the distance between the end face of the conductive layer and the end face of the ceramic body adjacent to it is denoted as d3; d1 is greater than d3, and d3 is greater than d2.

[0009] In a preferred embodiment of the present invention, d1 is 12% to 35% of the length of the ceramic body; d2 is 2% to 22% of the length of the ceramic body; and d3 is 5% to 25% of the length of the ceramic body.

[0010] As a preferred embodiment of the present invention, the thickness of the connecting electrode and the bottom electrode is 5μm to 60μm; the thickness of the insulating layer is 5μm to 20μm; and the thickness of the conductive layer is preferably 0.1μm to 0.5μm.

[0011] As a preferred embodiment of the present invention, the ceramic body includes stacked dielectric layers and internal electrodes disposed between two adjacent dielectric layers. The internal electrodes include a first internal electrode and a second internal electrode. One end of the first internal electrode is connected to one of the end electrodes, and the end of the first internal electrode is at a distance from the other end electrode. One end of the second internal electrode is connected to the other end electrode, and the end of the second internal electrode is at a distance from the end electrode connected to the first internal electrode. The first internal electrode and the second internal electrode are alternately disposed.

[0012] Furthermore, another aspect of the present invention provides a method for preparing a multilayer ceramic capacitor, comprising the following steps:

[0013] Step 1: Prepare the ceramic body;

[0014] Step 2: Set end electrodes at both ends of the ceramic body: Impregnate both ends of the ceramic body with metal slurry and heat to sinter, so that the metal slurry forms the bottom electrode of the connecting electrode and the welding electrode in the end electrode of the ceramic body; wherein, the end electrode includes a connecting electrode and a welding electrode, the connecting electrode covers the end face of the ceramic body and extends to the outer peripheral side of the ceramic body, and the welding electrode is arranged around the outer peripheral side and connected to the end face of the connecting electrode;

[0015] Step 3: Prepare an insulating layer on the connecting electrode, and the distance between the end face of the connecting electrode and the end face of the ceramic body adjacent to it is equal to the distance between the end face of the insulating layer and the end face of the ceramic body adjacent to it.

[0016] Step 4: A middle layer electrode is formed by electroplating on the bottom layer electrode, and then a top layer electrode is formed by electroplating on the middle layer electrode. The welding electrode includes a bottom layer electrode, a middle layer electrode and a top layer electrode arranged sequentially from the inside to the outside.

[0017] Step 5: Prepare a conductive layer on the insulating layer by sputtering, and the conductive layer completely covers the insulating layer and extends to the top electrode of the welding electrode.

[0018] In a preferred embodiment of the present invention, the connecting electrode is a copper electrode, the bottom electrode is a copper electrode layer, the middle electrode is a nickel electrode layer, and the top electrode is a tin electrode layer.

[0019] As a preferred embodiment of the present invention, step 1 includes the following specific steps:

[0020] Step 1.1: Prepare ceramic films using ceramic slurry as raw material;

[0021] Step 1.2: Print the inner electrode paste on the ceramic film to form an inner electrode pattern, and dry the inner electrode paste to obtain a ceramic film with inner electrodes.

[0022] Step 1.3: Stack multiple ceramic films with internal electrodes in a predetermined number, and cover the top and bottom sides of the stacked structure with protective layers to obtain a ceramic substrate; wherein the protective layer includes at least one ceramic film obtained in step 1.1.

[0023] Step 1.4: Press and cut the ceramic substrate to obtain multiple ceramic sheets;

[0024] Step 1.5: Remove the binder from the ceramic sheet and sinter it to obtain the ceramic body.

[0025] Compared with the prior art, the multilayer ceramic capacitor and its preparation method of this invention have the following advantages:

[0026] This invention prevents plating solution from seeping into the ceramic body during subsequent electroplating operations by setting an insulating layer. The plating solution can only enter along the end electrode not covered by the insulating layer, and the penetration direction of the plating solution is limited to the end electrode. This results in a narrow penetration surface and a long penetration path, preventing the plating solution from reaching the inner electrode exposed in the ceramic body. Therefore, it avoids the situation where plating solution seeps into the ceramic body and causes a decrease in the insulation resistance of the multilayer ceramic capacitor. Furthermore, a conductive layer is set on the surface of the insulating layer. The conductive layer can conduct electricity with the end electrode and form a reliable electrical connection with the inner electrode in the ceramic body, which facilitates automated electrical performance sorting of multilayer ceramic capacitors. In addition, the multilayer ceramic capacitor is soldered to the circuit board through the end electrode with the exposed conductive layer. This results in a small connection area between the multilayer ceramic capacitor and the circuit board and a small distance between the two solder joints, which can effectively suppress the transmission of piezoelectric vibration of the multilayer ceramic capacitor to the circuit board and reduce the noise of the circuit board. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below.

[0028] Figure 1 This is a schematic diagram of an existing multilayer ceramic capacitor welded onto a circuit board;

[0029] Figure 2 This is a schematic diagram of the plating solution penetration path of an existing multilayer ceramic capacitor;

[0030] Figure 3 This is a perspective view of a multilayer ceramic capacitor provided by the present invention;

[0031] Figure 4 This is a schematic diagram of the structure of a multilayer ceramic capacitor provided by the present invention;

[0032] Figure 5 This is a schematic diagram of the structure of the multilayer ceramic capacitor welded to the circuit board provided by the present invention;

[0033] Figure 6 This is a schematic diagram of the plating solution penetration path of the multilayer ceramic capacitor provided by the present invention;

[0034] In the figure, 1 is the ceramic body; 11 is the dielectric layer; 12 is the inner electrode; 13 is the end face of the ceramic body; 14 is the side face of the ceramic body; 2 is the end electrode; 21 is the connecting electrode; 22 is the welding electrode; 3 is the insulating layer; 4 is the conductive layer; 7 is the circuit board; 71 is the solder; 72 is the pad. Detailed Implementation

[0035] 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.

[0036] In the description of this invention, it should be understood that the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and 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 this invention.

[0037] like Figures 3-5 As shown, a preferred embodiment of the present invention provides a multilayer ceramic capacitor, comprising a ceramic body 1 and two end electrodes 2 respectively disposed on two end faces of the ceramic body 1. The end electrodes 2 extend to the outer peripheral side surface of the ceramic body 1, and the ends of the two end electrodes 2 are disposed opposite each other with a distance between them. An insulating layer 3 is covered on the end electrodes 2, and a conductive layer 4 is covered on the insulating layer 3. The conductive layer 4 covers the insulating layer 3 and extends to the end electrodes 2, with the ends of the end electrodes 2 exposed in the conductive layer 4. Preferably, the ceramic body 1 has a cuboid structure, and the end electrodes 2 extend to the four sides of the ceramic body 1.

[0038] For example, the end electrode 2 includes a connecting electrode 21 and a welding electrode 22. The connecting electrode 21 covers the end face 13 of the ceramic body 1 and extends to the outer peripheral side surface of the ceramic body 1. The welding electrode 22 is circumferentially disposed on the outer peripheral side surface and connected to the end face of the connecting electrode 21. The connecting electrode 21 is a single-layer electrode, and the welding electrode 22 is a composite-layer electrode. The insulating layer 3 covers the connecting electrode 21, and the conductive layer 4 completely covers the insulating layer 3 and extends to the welding electrode 22. The conductive layer 4 completely covers the insulating layer 3 and forms a conductive path with the welding electrode 22, the connecting electrode 21, and the inner electrode 12 of the ceramic body 1. In this way, the electrical parameters of the multilayer ceramic capacitor can be measured simply by contacting the conductive layer 4 on the multilayer ceramic capacitor with a test probe, thereby enabling automated electrical performance sorting. Specifically, the connecting electrode 21 is a copper electrode; the welding electrode 22 includes a bottom electrode, a middle electrode, and a top electrode arranged sequentially from the inside out. The bottom electrode is a copper electrode layer, the middle electrode is a nickel electrode layer, and the thickness of the nickel electrode layer is preferably 2μm to 5μm; the top electrode is a tin electrode layer, and the thickness of the tin electrode layer is preferably 5μm to 10μm. The nickel electrode layer can protect the copper electrode layer and prevent leaching during welding; the tin electrode layer at the top can act as a flux. Since the connecting electrode 21 in the terminal electrode 2 is completely covered by the insulating layer 3, the plating solution cannot directly penetrate into the connecting electrode 21. However, the plating solution may penetrate into the welding electrode 22 and thus indirectly penetrate into the connecting electrode 21 adjacent to the welding electrode 22. However, unlike the multilayer ceramic capacitors of the prior art, when the plating solution penetrates, the penetration direction is roughly perpendicular to the copper layer, the penetration surface is large and the penetration path is short. Therefore, the plating solution easily penetrates into the ceramic body 1, causing a decrease in insulation resistance. In this embodiment, the connecting electrode 21 of the multilayer ceramic capacitor extends a distance on the four sides of the ceramic body 1. The plating solution penetration direction is along the copper layer, the penetration surface is narrow, and the penetration source is located at the end face of the connecting electrode 21. The penetration path is long. Therefore, the plating solution cannot reach the inner electrode 12 exposed on the two end faces of the ceramic body 1, so it will not cause a decrease in insulation resistance. Of course, in other embodiments, the conductive layer 4 may partially cover the insulating layer 3, and the conductive layer 4 may extend to the welding electrode 22, ensuring that the conductive layer 4 achieves a conductive path through the end electrode 2 and the inner electrode 12, so as to enable automated electrical performance sorting of multilayer ceramic capacitors.

[0039] For example, the material of the conductive layer 4 is any one of copper, nickel, copper-nickel alloy, nickel-chromium alloy, nickel-vanadium alloy, titanium-tungsten alloy, and indium-gallium alloy, avoiding the use of materials such as tin, gold, and silver that are easily soldered. The thickness of the conductive layer 4 is preferably 0.1μm to 0.5μm. If the thickness of the conductive layer 4 is too small, the conductivity may be poor, while if the thickness of the conductive layer 4 is too large, it may hinder the soldering of the welding electrode 22. The outermost layer of the welding electrode 22 is a tin layer, which acts as a flux and is easy to solder during welding. The material of the conductive layer 4 is a metal or alloy with relatively low solderability, and the conductive layer 4 is not soldered during welding. Therefore, only the welding electrode 22 is soldered. The connection area between the multilayer ceramic capacitor and the circuit board 7 is significantly reduced compared to the prior art, which can suppress the transmission of piezoelectric vibration of the multilayer ceramic capacitor to the circuit board 7 and suppress the noise of the circuit board 7. If the extension distance of the terminal electrode 2 and the insulating layer 3 on the four sides of the ceramic body 1 is increased, the two welding electrodes 22 can be brought closer to each other, and the distance between the two solder points will be reduced accordingly, thereby further reducing the vibration of the circuit board 7 and reducing the buzzing noise.

[0040] and Figure 1 The diagram illustrates the soldering of an existing multilayer ceramic capacitor to a circuit board 7'. All four sides of the existing multilayer ceramic capacitor can be used as soldering surfaces. Since the outer layer of the entire terminal electrode 2' is a tin layer, the solder will rise to the two end faces of the multilayer ceramic capacitor during soldering, thereby increasing the connection area between the multilayer ceramic capacitor and the circuit board 7'. Furthermore, the distance between the solder joints at both ends is relatively large. As a result, a large amount of piezoelectric vibration generated by the multilayer ceramic capacitor will be transmitted to the circuit board 7', exacerbating the vibration and noise of the circuit board 7'.

[0041] For example, the distance between the end face of the welding electrode 22 and the end face 13 of the ceramic body 1 adjacent to it is denoted as d1; the distance between the end face of the connecting electrode 21 and the end face 13 of the ceramic body 1 adjacent to it is denoted as d2, and the distance between the end face of the connecting electrode 21 and the end face 13 of the ceramic body 1 adjacent to it is equal to the distance between the end face of the insulating layer 3 and the end face 13 of the ceramic body 1 adjacent to it; the distance between the end face of the conductive layer 4 and the end face 13 of the ceramic body 1 adjacent to it is denoted as d3; d1 is greater than d3, and d3 is greater than d2. Specifically, d1 is 12% to 35% of the length of the ceramic body 1. If d1 is too small, it is not convenient to solder multilayer ceramic capacitors on the circuit board 7. If d1 is too large, the two terminal electrodes 2 are easily short-circuited. d2 is 2% to 22% of the length of the ceramic body 1. If d2 is too small, the effect of preventing plating solution penetration is insufficient. If d2 is too large, it is not convenient to solder multilayer ceramic capacitors on the circuit board 7. d3 is 5% to 25% of the length of the ceramic body 1. If d3 is too small, it is not convenient for the conductive layer 4 to form a reliable electrical connection with the soldering electrode 22. If d3 is too large, the conductive layer 4 covers the soldering electrode 22 too much, which makes it not convenient to solder multilayer ceramic capacitors on the circuit board 7.

[0042] For example, the thickness of the connecting electrode 21 and the bottom electrode is preferably 5μm to 60μm. If the thickness of the connecting electrode 21 and the bottom electrode is too small, the continuity of the copper layer will be poor, which is not conducive to conductivity. If the thickness of the connecting electrode 21 and the bottom electrode is too large, it will not be conducive to reducing the volume of the multilayer ceramic capacitor. The thickness of the insulating layer 3 is 5μm to 20μm. If the thickness of the insulating layer 3 is too small, the effect of preventing plating solution penetration will be insufficient. If the thickness of the insulating layer 3 is too large, it will not be conducive to reducing the volume of the multilayer ceramic capacitor. The insulating layer 3 is preferably a ceramic insulating layer 3 or a resin insulating layer 3.

[0043] Specifically, the ceramic body 1 includes stacked dielectric layers 11 and inner electrodes 12 disposed between two adjacent dielectric layers 11. The inner electrodes 12 include a first inner electrode 12 and a second inner electrode 12. One end of the first inner electrode 12 is connected to one of the end electrodes 2, and the end of the first inner electrode 12 is at a distance from the other end electrode 2. One end of the second inner electrode 12 is connected to the other end electrode 2, and the end of the second inner electrode 12 is at a distance from the end electrode 2 connected to the first inner electrode 12. The first inner electrode 12 and the second inner electrode 12 are alternately disposed.

[0044] like Figures 3-5 As shown, the present invention also provides a method for preparing a multilayer ceramic capacitor, which includes the following steps:

[0045] Step 1: Prepare ceramic body 1;

[0046] Step 2: Set end electrodes 2 at both ends of the ceramic body 1: Impregnate both ends of the ceramic body 1 with copper paste and heat and sinter the copper paste in a neutral atmosphere (such as nitrogen atmosphere) to form the bottom electrode of the connecting electrode 21 and the welding electrode 22 in the end electrodes 2 at both ends of the ceramic body 1; wherein, the end electrode 2 includes the connecting electrode 21 and the welding electrode 22, the connecting electrode 21 covers the end face 13 of the ceramic body 1 and extends to the outer peripheral side surface of the ceramic body 1, the welding electrode 22 is arranged around the outer peripheral side surface and connected to the end face of the connecting electrode 21, the connecting electrode 21 is a copper electrode, and the bottom electrode is a copper electrode layer, that is, the connecting electrode 21 and the bottom electrode are integrally formed by heating and sintering copper paste;

[0047] Step 3: An insulating layer 3 is prepared on the connecting electrode 21, and the distance between the end face of the connecting electrode 21 and the end face 13 of the ceramic body 1 adjacent to it is equal to the distance between the end face of the insulating layer 3 and the end face 13 of the ceramic body 1 adjacent to it; the insulating layer 3 is preferably a ceramic insulating layer 3 or a resin insulating layer 3. When the insulating layer 3 is a ceramic insulating layer 3, it can be formed on the two connecting electrodes 21 of the ceramic body 1 by sputtering; when the insulating layer 3 is a resin insulating layer 3, it can be formed on the two connecting electrodes 21 of the ceramic body 1 by impregnation.

[0048] Step 4: A middle layer electrode is formed by electroplating on the bottom layer electrode, and then a top layer electrode is formed by electroplating on the middle layer electrode. The middle layer electrode is a nickel electrode layer; the top layer electrode is a tin electrode layer; wherein, the welding electrode 22 includes a bottom layer electrode, a middle layer electrode and a top layer electrode arranged sequentially from the inside to the outside.

[0049] Step 5: Prepare a conductive layer 4 on the insulating layer 3 by sputtering, and the conductive layer 4 completely covers the insulating layer 3 and extends to the top electrode of the welding electrode 22.

[0050] The distance between the end face of the welding electrode 22 and the end face 13 of the ceramic body 1 adjacent to it is denoted as d1; the distance between the end face of the connecting electrode 21 and the end face 13 of the ceramic body 1 adjacent to it is denoted as d2, and the distance between the end face of the connecting electrode 21 and the end face 13 of the ceramic body 1 adjacent to it is equal to the distance between the end face of the insulating layer 3 and the end face 13 of the ceramic body 1 adjacent to it; the distance between the end face of the conductive layer 4 and the end face 13 of the ceramic body 1 adjacent to it is denoted as d3; d1 is greater than d3, and d3 is greater than d2. Specifically, d1 is 12% to 35% of the length of the ceramic body 1. If d1 is too small, it is not convenient to solder multilayer ceramic capacitors on the circuit board 7. If d1 is too large, the two terminal electrodes 2 are easily short-circuited. d2 is 2% to 22% of the length of the ceramic body 1. If d2 is too small, the effect of preventing plating solution penetration is insufficient. If d2 is too large, it is not convenient to solder multilayer ceramic capacitors on the circuit board 7. d3 is 5% to 25% of the length of the ceramic body 1. If d3 is too small, it is not convenient for the conductive layer 4 to form a reliable electrical connection with the soldering electrode 22. If d3 is too large, the conductive layer 4 covers the soldering electrode 22 too much, which makes it not convenient to solder multilayer ceramic capacitors on the circuit board 7.

[0051] Furthermore, step 1 includes the following specific steps:

[0052] Step 1.1: Prepare a ceramic film using ceramic slurry as raw material. The ceramic film is the dielectric layer 11 mentioned above. Specifically, mix ceramic powder, binder and organic solvent and disperse them evenly by ball milling or sand milling to obtain ceramic slurry. Then cast the ceramic slurry into a ceramic film.

[0053] Step 1.2: Print the inner electrode 12 paste onto the ceramic film to form an inner electrode 12 pattern, and dry the inner electrode 12 paste to obtain a ceramic film with inner electrodes 12; specifically: use screen printing or gravure printing to print the inner electrode 12 paste onto the ceramic film to form an inner electrode 12 pattern on one side surface of the ceramic film, and dry the inner electrode 12 paste to obtain a ceramic film with inner electrodes 12; wherein, the inner electrode 12 paste is a nickel paste;

[0054] Step 1.3: Stack multiple ceramic films with internal electrodes 12 in a predetermined number, and cover the upper and lower sides of the stacked structure with protective layers to obtain a ceramic substrate; wherein, the protective layer includes at least one ceramic film obtained in step 1.1; in addition, the number of ceramic films with internal electrodes 12 stacked is not limited, but in order to obtain a higher capacitance, it is preferred to have 80 or more layers.

[0055] Step 1.4: Press and cut the ceramic substrate to obtain multiple ceramic sheets; specifically: press the ceramic substrate using isostatic pressing, and then cut the ceramic substrate longitudinally and transversely according to a predetermined size to obtain multiple rectangular ceramic sheets. Each ceramic sheet includes two oppositely arranged end faces, with one set of internal electrodes 12 (first internal electrodes) exposed on one end face of the ceramic sheet, and another set of internal electrodes 12 (second internal electrodes) exposed on the other end face of the ceramic sheet;

[0056] Step 1.5: Remove the binder from the ceramic sheet and sinter to obtain ceramic body 1; specifically: First, perform a binder removal operation. This involves heating the ceramic sheet in air to 250℃-350℃ and holding it at that temperature for 0.5 hours to 3 hours to remove the binder contained in the ceramic sheet, or heating the ceramic sheet in nitrogen to 350℃-600℃ and holding it at that temperature for 2 hours to 6 hours to remove the binder contained in the ceramic sheet. Then, perform sintering. Sintering is carried out in a reducing atmosphere formed by a mixture of humidified nitrogen and hydrogen (the volume of hydrogen is 0.1%-3% of the volume of nitrogen). The ceramic sheet is heated to 1100℃-1300℃ and held at that temperature for 0.5 hours to 3 hours to sinter the ceramic sheet into ceramic, obtaining ceramic body 1.

[0057] like Figure 6 As shown, the penetration path of the plating solution during electroplating of the multilayer ceramic capacitor in this embodiment is as follows: Figure 6 The arrows indicate the location, while the dashed boxes indicate that the plating solution penetrating to that location would cause a decrease in insulation resistance. Because the penetration path of the plating solution is long, it cannot reach the inner electrode 12 exposed at the end face of the ceramic body 1, thus not causing a decrease in insulation resistance. Figure 2 As shown, the penetration path of the plating solution during electroplating of existing multilayer ceramic capacitors is as follows: Figure 2 The arrows indicate that the plating solution will penetrate to that location and cause a decrease in insulation resistance. Existing multilayer ceramic capacitors have short plating solution penetration paths, so the plating solution can easily penetrate into the ceramic body, leading to a decrease in insulation resistance of the multilayer ceramic capacitor, or even short circuit and burnout.

[0058] In summary, by setting the insulating layer 3, the present invention can prevent the plating solution from seeping in during subsequent electroplating operations. The plating solution can only enter along the end of the terminal electrode 2 not covered by the insulating layer 3, and the direction of plating solution penetration can only be along the terminal electrode 2. This results in a narrow penetration surface and a long penetration path, preventing the plating solution from reaching the inner electrode 12 exposed in the ceramic body 1. Therefore, it can avoid the situation where the plating solution seeps into the ceramic body 1 and causes a decrease in the insulation resistance of the multilayer ceramic capacitor. Moreover, a conductive layer 4 is set on the surface of the insulating layer 3. The conductive layer 4 can conduct electricity with the terminal electrode 2 and thus form a reliable electrical connection with the inner electrode 12 in the ceramic body 1, which facilitates the automated electrical performance sorting of the multilayer ceramic capacitor. In addition, the multilayer ceramic capacitor is soldered to the circuit board 7 through the end of the terminal electrode 2 exposed by the conductive layer 4. This makes the connection area between the multilayer ceramic capacitor and the circuit board 7 small and the distance between the two solder points small, which can effectively suppress the piezoelectric vibration of the multilayer ceramic capacitor transmitted to the circuit board 7 and reduce the noise of the circuit board 7.

[0059] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" 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.

[0060] 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 two end electrodes respectively disposed on the two end faces of the ceramic body. The end electrodes extend to the outer peripheral side surface of the ceramic body, and the ends of the two end electrodes are disposed opposite each other with a distance between them. An insulating layer is covered on the end electrodes, and a conductive layer is covered on the insulating layer. The conductive layer covers the insulating layer and extends to the end electrodes, with the end of the end electrodes exposed outside the conductive layer. The end electrodes include a connecting electrode and a welding electrode. The connecting electrode covers the end face of the ceramic body and extends to the outer peripheral side surface of the ceramic body. The welding electrode is circumferentially disposed on the outer peripheral side surface and connected to the end face of the connecting electrode. The connecting electrode is a single-layer electrode, and the welding electrode is a composite-layer electrode. The insulating layer covers the connecting electrode, and the conductive layer completely covers the insulating layer and extends to the welding electrode. The electrode is a copper electrode; the welding electrode includes a bottom electrode, a middle electrode, and a top electrode arranged sequentially from the inside out. The bottom electrode is a copper electrode layer, the middle electrode is a nickel electrode layer, and the top electrode is a tin electrode layer. The conductive layer is made of any one of copper, nickel, copper-nickel alloy, nickel-chromium alloy, nickel-vanadium alloy, titanium-tungsten alloy, and indium-gallium alloy. The distance between the end face of the welding electrode and the end face of the ceramic body adjacent to it is denoted as d1. The distance between the end face of the connecting electrode and the end face of the ceramic body adjacent to it is denoted as d2, and the distance between the end face of the connecting electrode and the end face of the ceramic body adjacent to it is equal to the distance between the end face of the insulating layer and the end face of the ceramic body adjacent to it. The distance between the end face of the conductive layer and the end face of the ceramic body adjacent to it is denoted as d3. d1 is greater than d3, and d3 is greater than d2.

2. The multilayer ceramic capacitor as described in claim 1, characterized in that, The d1 is 12% to 35% of the length of the ceramic body; the d2 is 2% to 22% of the length of the ceramic body; and the d3 is 5% to 25% of the length of the ceramic body.

3. The multilayer ceramic capacitor as described in claim 1, characterized in that, The thickness of the connecting electrode and the bottom electrode is 5μm~60μm; the thickness of the insulating layer is 5μm~20μm.

4. The multilayer ceramic capacitor as described in claim 3, characterized in that, The thickness of the conductive layer is 0.1μm to 0.5μm.

5. The multilayer ceramic capacitor as described in any one of claims 1 to 4, characterized in that, The ceramic body includes stacked dielectric layers and internal electrodes disposed between two adjacent dielectric layers. The internal electrodes include a first internal electrode and a second internal electrode. One end of the first internal electrode is connected to one of the end electrodes, and the end of the first internal electrode is at a distance from the other end electrode. One end of the second internal electrode is connected to the other end electrode, and the end of the second internal electrode is at a distance from the end electrode connected to the first internal electrode. The first internal electrode and the second internal electrode are alternately disposed.

6. A method for preparing a multilayer ceramic capacitor, characterized in that, Includes the following steps: Step 1: Prepare the ceramic body; Step 2: Set end electrodes at both ends of the ceramic body: Impregnate both ends of the ceramic body with metal slurry and heat to sinter, so that the metal slurry forms the bottom electrode of the connecting electrode and the welding electrode in the end electrode of the ceramic body; wherein, the end electrode includes a connecting electrode and a welding electrode, the connecting electrode covers the end face of the ceramic body and extends to the outer peripheral side of the ceramic body, and the welding electrode is arranged around the outer peripheral side and connected to the end face of the connecting electrode; Step 3: Prepare an insulating layer on the connecting electrode, and the distance between the end face of the connecting electrode and the end face of the ceramic body adjacent to it is equal to the distance between the end face of the insulating layer and the end face of the ceramic body adjacent to it. Step 4: A middle layer electrode is formed by electroplating on the bottom layer electrode, and then a top layer electrode is formed by electroplating on the middle layer electrode. The welding electrode includes a bottom layer electrode, a middle layer electrode and a top layer electrode arranged sequentially from the inside to the outside. Step 5: Prepare a conductive layer on the insulating layer by sputtering, and the conductive layer completely covers the insulating layer and extends to the top electrode of the welding electrode.

7. The method for preparing a multilayer ceramic capacitor as described in claim 6, characterized in that, The connecting electrode is a copper electrode, the bottom electrode is a copper electrode layer, the middle electrode is a nickel electrode layer, and the top electrode is a tin electrode layer.

8. The method for preparing a multilayer ceramic capacitor as described in claim 7, characterized in that, Step 1 includes the following specific steps: Step 1.1: Prepare ceramic films using ceramic slurry as raw material; Step 1.2: Print the inner electrode paste on the ceramic film to form an inner electrode pattern, and dry the inner electrode paste to obtain a ceramic film with inner electrodes. Step 1.3: Stack multiple ceramic films with internal electrodes in a predetermined number, and cover the top and bottom sides of the stacked structure with protective layers to obtain a ceramic substrate; wherein the protective layer includes at least one ceramic film obtained in step 1.

1. Step 1.4: Press and cut the ceramic substrate to obtain multiple ceramic sheets; Step 1.5: Remove the binder from the ceramic sheet and sinter it to obtain the ceramic body.

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