Multilayer ceramic capacitor and method for manufacturing the same

Abstract

The present invention provides a multilayer ceramic capacitor and a method for manufacturing the same, which includes a capacitor body and two external electrodes facing each other with a space therebetween. The capacitor body includes a plurality of first and second internal electrodes and a dielectric layer separating the first and second internal electrodes. The external electrode includes a seed layer and an electrode layer in order from the inside to the outside. The seed layer covers the outer surface of the portion where the external electrode is provided on the capacitor body. The electrode layer includes at least an electrode metal layer formed by plating and a welding metal layer formed by plating. By the seed layer of the present invention, the plating formation of the electrode metal layer can be facilitated. The electrode metal layer formed by plating has a uniform and thin thickness, and the stress is uniformly dispersed, preventing cracks from occurring in the external electrode. Further, since the electrode metal layer is formed by plating, the formation by sintering is avoided, the density is high, the penetration of nickel solution or the like is prevented, and the occurrence of cracks in the capacitor body is prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitors, and in particular, to multilayer ceramic capacitors and manufacturing methods thereof.

Background Art

[0002] As a conventional multilayer ceramic capacitor, for example, in the Chinese invention patent application CN114078634A, there is disclosed a multilayer ceramic capacitor including a capacitor body which is a sintered body obtained by alternately laminating and sintering a dielectric layer and internal electrodes, and external electrodes are provided at both ends of the capacitor body. The external electrodes of conventional capacitors generally include a copper layer, a nickel layer, and a tin layer from the inside to the outside. The forming process generally first obtains the copper layer by dipping into copper paste and sintering, then forms the nickel layer by electroplating, and finally forms the tin layer by electroplating. Therefore, the innermost copper layer is a sintered copper layer, the thickness of the sintered copper layer is thick and uneven, and if the sintered copper layer is too thin, the bonding force between the copper layer and both ends of the capacitor body will deteriorate. Therefore, the thickness of the copper layer must be set to 10 - 15 μm to ensure the bonding force between the copper layer and the capacitor body. However, doing so may lead to an increase in the electrode size and the enlargement of the capacitor.

[0003] Referring to FIG. 1, when manufacturing the copper layer of the external electrode, the capacitor body 10 is placed vertically, one end for adhering the copper paste 200 in the capacitor body 10 is directed downward and immersed in the copper paste 200. After lifting the capacitor body 10, the copper paste 200 adheres to the lower end of the capacitor body 10. When the capacitor body 10 with the adhered copper paste 200 is sintered, a copper layer of the external electrode can be formed at the end of the capacitor body 10. However, for the multilayer ceramic capacitor obtained by this manufacturing method, since the copper paste 200 has fluidity, in the process of lifting the capacitor body 10, the copper paste 200 adhered to the capacitor body 10 flows downward under the action of its own gravity, and the amount of the copper paste 200 adhered to the outer peripheral surface of the capacitor body 10 decreases, while the amount of the copper paste 200 on the end face increases, the copper layer distribution is non-uniform, the stress of the copper layer gathers near the edge of the copper layer, and cracks are likely to occur in the external electrode; because the external electrode on the outer peripheral surface of the capacitor body 10 is thin, the bonding force between the external electrode and the capacitor body 10 is weak, and the external electrode is likely to fall off from the capacitor body 10 under an external force impact; the distance along the vertical direction of the capacitor body 10 between the external electrodes at both ends of the capacitor body 10 is small, and it is easy to cause a short circuit of the external electrode, and there are such drawbacks.

[0004] When no external electrodes are formed on the multilayer ceramic capacitor, the internal cracking phenomenon is less likely to occur in the capacitor body 10. However, in the copper layer sintering process, due to the bonding stress between the copper layer and the capacitor body 10, the remaining stress is released, so there is often a problem that the sintered copper layer causes cracks in the capacitor body 10. On the other hand, when sintering the copper paste 200 in the multilayer ceramic capacitor, the resin in the copper paste 200 volatilizes to form cavities in the copper layer. In the process of nickel electroplating, a small amount of nickel metal liquid enters the cavities. In the subsequent application process of the multilayer ceramic capacitor product, the multilayer ceramic capacitor undergoes a reflow soldering process (SMT - surface mounting technology process). The heating temperature of the multilayer ceramic capacitor varies from 260° to 320°. Nickel metal remains inside the copper layer. Since the thermal expansion coefficients (thermal shrinkage rates) of both copper metal and nickel metal are different, the generated internal stress acts on the capacitor body 10 to cause cracks.

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a multilayer ceramic capacitor and a manufacturing method thereof that can solve at least one of the technical problems described in the above - mentioned background art and suppress the occurrence of cracks in the capacitor body and the occurrence of cracks in the external electrodes.

Means for Solving the Problems

[0006] The first technical means adopted by the present invention to solve the problems in the prior art is a multilayer ceramic capacitor including a capacitor body and two external electrodes provided on the capacitor body and facing each other with a gap therebetween. In the capacitor body, it includes a plurality of first internal electrodes, a plurality of second internal electrodes, and a dielectric layer separating the first internal electrodes and the second internal electrodes. In the multilayer ceramic capacitor, one end of the first internal electrode and one end of the second internal electrode are respectively exposed from the outer surface of the capacitor body and are electrically connected corresponding to the two external electrodes. The external electrode includes a seed layer and an electrode layer in order from the inside to the outside. The seed layer covers the outer surface of the portion where the external electrode is provided in the capacitor body. The outer surface where the seed layer is provided in the capacitor body is roughened to form a surface roughened layer having an uneven surface. The electrode layer is a multilayer ceramic capacitor including at least an electrode metal layer formed on the surface of the seed layer by plating and a welding metal layer formed by plating and located outside the electrode metal layer.

[0007] Furthermore, the first internal electrode and the second internal electrode are exposed from the seed layer and directly connected to the electrode metal layer.

[0008] Furthermore, the seed layer contains at least one seed metal of at least gold, silver, or platinum group metals.

[0009] Furthermore, the surface roughened layer has a roughness greater than the roughness of the outer surface of the portion where the external electrode is not provided in the capacitor body, and the seed metal of the seed layer is dispersed and distributed in the surface roughened layer at intervals.

[0010] Furthermore, the electrode metal layer is formed on the outer surface of the seed layer by a chemical plating forming method.

[0011] Furthermore, the portions of the first internal electrode and the second internal electrode exposed from the outer surface of the capacitor body are not roughened, and the first internal electrode and the second internal electrode are exposed from the surface roughened layer.

[0012] Furthermore, the seed metal is palladium metal.

[0013] Furthermore, the electrode metal layer is a copper metal layer or a nickel metal layer, and the thickness range of the electrode metal layer is 0.5 μm to 8 μm.

[0014] Furthermore, the seed metal of the seed layer is replaced with an electrode metal solution to deposit the electrode metal layer. The seed metal is replaced and reduced in amount, and the electrode metal layer is plated on the exposed portions from the outer surfaces of the surface roughened layers in the seed layer, the first internal electrode, and the second internal electrode.

[0015] Furthermore, the electrode layer further includes a protective layer made of a metal material formed on the outer surface of the electrode metal layer by chemical plating or electroplating.

[0016] Furthermore, the protective layer is a protective layer made of a nickel metal material.

[0017] Furthermore, the capacitor body includes two end faces facing each other in the longitudinal direction and an outer peripheral surface connecting the two end faces. The two external electrodes respectively cover the corresponding end faces and at least a part of the outer peripheral surface. One end of the first internal electrode and the second internal electrode is respectively exposed from the two end faces, and the edge of the electrode metal layer located on the outer peripheral surface forms a boundary edge extending linearly in the width direction perpendicular to the longitudinal direction.

[0018] Furthermore, the outer peripheral surface of the capacitor body where the external electrode is not provided is covered with a layer of protective film. The thickness of the protective film is equal to or greater than the thickness of the electrode metal layer, and the protective film shields at least the boundary edge of the electrode metal layer.

[0019] Furthermore, the protective film is formed of an insulating chemical material, and when the insulating chemical material is heat-treated, it penetrates into the gaps formed after sintering of the capacitor body.

[0020] Furthermore, the protective film is methyl silicone oil, and the thickness of the protective film is 0.3 - 5 um.

[0021] The second technical means adopted by the present invention to solve the conventional technical problems is A multilayer ceramic capacitor including a capacitor body and two external electrodes provided on the capacitor body and facing each other with a gap therebetween, wherein the capacitor body includes a plurality of first internal electrodes, a plurality of second internal electrodes, and a dielectric layer separating the first internal electrodes and the second internal electrodes, and one end of the first internal electrode and one end of the second internal electrode are each exposed from the outer surface of the capacitor body. In the manufacturing method of the multilayer ceramic capacitor, Step 1 of performing a surface roughening treatment on the outer surface of the portion of the capacitor body where the external electrode is provided to form a surface roughening layer having an uneven surface; Step 2 of immersing at least the outer surface of the capacitor body provided with the surface roughening layer in a solution of an ion catalyst containing at least one kind of seed metal ion of gold, silver, or a platinum group metal, and adsorbing the seed metal ions in the ion catalyst on the outer surface of the surface roughening layer; Step 3 of immersing at least the outer surface of the capacitor body provided with the surface roughening layer in a reducing chemical solution to reduce the adsorbed seed metal ions to a seed metal, and fixing the reduced seed metal on the outer surface of the surface roughening layer to form a seed layer; Step 4 of plating the seed layer to form an electrode metal layer; Step 5 of plating outside the electrode metal layer to form a welding metal layer. This is a manufacturing method of a multilayer ceramic capacitor.

[0022] Furthermore, after step 4 and before step 5, it further includes a step of forming a protective layer made of a nickel metal layer with a thickness of 2 - 5 μm on the outer surface of the electrode metal layer by a method of chemical plating or electroplating.

[0023] Furthermore, the welding metal layer is a tin metal layer formed by a method of chemical plating or electroplating, and the thickness of the tin metal layer is 2 - 5 μm.

[0024] Furthermore, in the plating method of step 4, at least the outer surface of the capacitor body provided with the surface roughening layer is immersed in an electrode metal solution, and the electrode metal in the electrode metal solution replaces a part of the seed metal, and the electrode metal is deposited and plated on the exposed portions of the capacitor body from the outer surface of the seed layer, the first internal electrode, and the second internal electrode, so as to form the electrode metal layer.

[0025] Furthermore, the surface roughening treatment is performed by means of sandblasting, laser beam irradiation, or heating. 。

[0026] Furthermore, after step 1 and before step 2, the method further includes immersing the surface roughening layer of the capacitor body in an activating chemical solution to perform a surface activation treatment, so as to improve the adsorption ability of the capacitor body to the ion catalyst.

[0027] Furthermore, before step 1, the method further includes a pretreatment step 2 of immersing the capacitor body in an insulating chemical solution to coat the entire outer surface of the capacitor body with a layer of protective film formed of an insulating chemical material.

[0028] Furthermore, when the protective film is heat-treated, the insulating chemical material in the protective film penetrates into the gaps formed on the outer surface of the capacitor body after sintering.

[0029] Furthermore, the protective film is made of methyl silicone oil material.

[0030] Furthermore, after the surface roughening treatment, the portion of the protective film corresponding to the location where the external electrode of the capacitor body is provided is removed, and the portion of the protective film corresponding to the location where the external electrode of the capacitor body is not provided is left.

[0031] Furthermore, before the pretreatment step 2, the method further includes a pretreatment step 1 of performing a cleaning treatment on the entire capacitor body.

[0032] Furthermore, after the step 2 and before the step 3, a step of performing a cleaning process on the capacitor body to wash away the seed metal ions adhering to the outer surfaces of the first internal electrode, the second internal electrode, and the protective film is further included.

Advantages of the Invention

[0033] The beneficial effects of the present invention are as follows. The seed layer of the multilayer ceramic capacitor of the present invention can facilitate the plating formation of the electrode metal layer. The thickness of the electrode metal layer formed by plating is uniform and thin, the stress is uniformly distributed, and the occurrence of cracks in the external electrode is prevented. In addition, since the electrode metal layer is formed by plating, the formation by sintering is avoided, the density is high, the penetration of nickel solution and the like is prevented, and the occurrence of cracks in the capacitor body is prevented.

Brief Description of the Drawings

[0034] The above-mentioned object, technical means, and beneficial effects of the invention can be realized by the following attached drawings.

[0035]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Embodiments for Carrying Out the Invention

[0036] Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings of the embodiments.

[0037] Referring simultaneously to FIGS. 2 to 7, the first preferred embodiment of the present invention provides a multilayer ceramic capacitor 100 including a capacitor body 10, two external electrodes 20 provided on two end faces 13 facing each other in the longitudinal direction of the capacitor body 10, respectively, and a protective film 30 located on the outer surface between the two external electrodes 20 that covers the capacitor body 10.

[0038] The capacitor body 10 includes a plurality of stacked dielectric layers 14 and internally electrodes stacked alternately, and the internally electrodes include a first internal electrode 151 and a second internal electrode 153. The dielectric layer 14 is generally manufactured from a ceramic dielectric material. The outer end surfaces of the first internal electrode 151 and the second internal electrode 153 are exposed from two end surfaces 13 of the capacitor body 10 respectively. The first internal electrode 151 and the second internal electrode 153 are provided at intervals alternately, the dielectric layer 14 is interposed between the adjacent first internal electrode 151 and second internal electrode 153, and together with the first internal electrode 151 and the second internal electrode 153, they constitute the effective region of the multilayer ceramic capacitor 100. The first internal electrode 151 and the second internal electrode 153 may be metal electrodes made of nickel, silver or copper materials. The capacitor body 10 has an outer peripheral surface 11 connecting two opposite end surfaces 13. The external electrode 20 includes at least two electrode layer structures of an electrode metal layer 27 located in the inner layer and a welding metal layer 28 located in the outermost layer.

[0039] The two external electrodes 20 cover the corresponding end surfaces 13 and at least a part of the outer peripheral surface 11 respectively, and the two external electrodes 20 are electrically connected to the outer end surfaces of the first internal electrode 151 and the second internal electrode 153 respectively.

[0040] In the present embodiment, specifically, the electrode layer of the external electrode 20 includes an electrode metal layer 27 and a welding metal layer 28, each including an end wall 21 and a peripheral wall 23 connected to the periphery of the end wall 21 and extending toward the same side of the end wall 21. The end wall 21 covers the end surface 13 of the corresponding capacitor body 10, and the peripheral walls 23 of the two external electrodes 20 cover both opposite ends of the outer peripheral surface 11 respectively. The electrode metal layer 27 may be a chemically plated copper metal layer, and in other embodiments, the electrode metal layer 27 may be a nickel metal layer formed by chemical plating. The welding metal layer 28 is a tin metal layer formed by chemical plating or electroplating so as to facilitate electric welding. It is understood that in the external electrode 20, an additional layer such as a conductive resin electrode layer may be provided between the two-layer structure to reduce mechanical shock and the like. In the present embodiment, one end of the peripheral wall 23 of the external electrode 20 away from the end wall 21 forms a boundary edge 25.

[0041] When a voltage is applied between the two external electrodes 20, the external electrodes 20 conduct the first internal electrode 1 51 and the second internal electrode 153, and further the voltage is applied to the plurality of dielectric layers 14 between the first internal electrode 151 and the second internal electrode 153, whereby charges are accumulated in the multilayer ceramic capacitor 100 to generate a capacitance value.

[0042] In order to uniformly form the electrode metal layer 27 of the external electrode 20 and avoid the occurrence of cracks in the external electrode 20 or internal cracking in the capacitor body 10, in this embodiment, the external electrode 20 includes a seed layer 26 (or catalyst layer), the electrode metal layer 27, and a welding metal layer 28 in order from the inside to the outside. The seed layer 26 contains at least one seed metal 310 of gold, silver, or platinum group metals (for example, metals such as ruthenium, rhodium, palladium, osmium, iridium, and platinum). The seed layer 26 is thin and is distributed in a dispersed manner at intervals. After replacing the electrode metal (copper metal or nickel metal) in the electrode metal layer 27, the seed metal 310 in the seed layer 26 becomes even less, and is formed in a dispersed manner on the surface roughened layer 29 of the capacitor body 10 and the first internal electrode 151 and the second internal electrode 153. The electrode metal layer 27 is formed by chemical plating based on the seed layer 26. The electrode metal layer 27 formed by chemical plating can have a significantly reduced thickness. When the electrode metal layer 27 formed by chemical plating is a copper metal layer, the thickness of the copper metal layer can be 7 - 8 μm, and in the thinnest case, it can be 0.5 - 0.6 μm. This can greatly reduce the thickness of the external electrode 20 and reduce the internal stress of the electrode metal layer 27. The electrode metal layer 27 formed by chemical plating has a uniform thickness and the stress does not gather near the end face 13 of the capacitor body 10 but is uniformly dispersed, thus avoiding the occurrence of cracks in the capacitor body 10. Also, the electrode metal layer 27 formed by chemical plating has high density and can prevent moisture and welding metal (for example, nickel solution) from penetrating. A protective film 30 is formed on the capacitor body 10 between the external electrodes 20. The protective film 30 can further prevent moisture and welding metal (for example, metals such as tin and nickel) from penetrating into the external electrode 20 at the boundary edge 25 of the electrode metal layer 27, and can prevent short - circuiting between the external electrodes 20 at two opposite ends.

[0043] In this embodiment, the electrode layer of the external electrode 20 includes at least a three-layer structure of an electrode metal layer 27 formed by plating (specifically, a chemically plated copper layer is adopted in this embodiment), a protective layer 33 made of a metal protective material (specifically, an electroplated nickel layer is adopted in this embodiment), and a welding metal layer 28 formed by plating (specifically, a chemically / electroplated tin layer is adopted in this embodiment), or includes at least a two-layer structure of an electrode metal layer 27 formed by plating (specifically, a chemically plated nickel layer may be adopted in this embodiment) and a welding metal layer 28 formed by plating (specifically, a chemically / electroplated tin layer is adopted in this embodiment).

[0044] In this embodiment, the seed layer 26 is not formed on the portion exposed from the end face 13 of the internal electrode, and the electrode metal layer 27 is directly connected to the portion exposed from the end face 13 of the internal electrode.

[0045] In this embodiment, the protective film 30 may have a thickness equal to or greater than the thickness of the electrode metal layer 27, and in other embodiments, the protective film 30 may have a thickness equal to or greater than the thickness of the external electrode 20.

[0046] In this embodiment, the boundary edge 25 of the electrode metal layer 27 on the upper and lower surfaces of the capacitor body 10 is linear along the width direction perpendicular to the longitudinal direction, increasing the insulation distance L2 between the two external electrodes 20 and preventing electrical interruption or short circuit between the external electrodes 20.

[0047] The shape of the capacitor body 10 is not limited to the rectangular parallelepiped of this embodiment. For example, the surface of the capacitor body 10 may be a curved surface, or the shape of the capacitor body 10 may be a cylindrical body as a whole, or the eight corners of the capacitor body 10 may be rounded corners, chamfered corners, etc. It is understood that this is also possible.

[0048] In other embodiments, it is understood that the number of internal electrodes, the thickness of the dielectric layer 14, etc. can be determined according to the size and performance requirements necessary for the capacitor 100.

[0049] Specifically, the second preferred embodiment of the present invention further provides a method for molding the multilayer ceramic capacitor 100, and the specific method is as follows.

[0050] Step 1: Perform a pretreatment process including cleaning and the like on the capacitor body 10.

[0051] Step 2: Cover the entire outer peripheral surface 11 and end face 13, which are the outer surfaces of the capacitor body 10, with a single layer of protective film 30. For details, please refer to FIG. 5. Specifically, immerse the capacitor body 10 in an insulating chemical solution for forming the protective film 30 to cover the outer peripheral surface 11 of the capacitor body 10 with a single layer of thin protective film 30. The thickness of the protective film 30 may be 0.3 - 5 um, but is not limited thereto and can be adjusted according to the thickness of the electrode metal layer 27 or the external electrode 20. The protective film 30 has characteristics such as waterproofness, high temperature resistance, and insulation. In one of its embodiments, the protective film is a silicone oil material layer. The silicone oil has high hydrophobicity, a small temperature-dependent viscosity coefficient, excellent high and low temperature resistance, can prevent oxidation, has a high flash point, low volatility, high insulation, low surface tension, and no corrosivity or toxicity to metals. It is understood that the silicone oil includes methyl silicone oil, methyl phenyl silicone oil, various functional silicone oils, and modified silicone oils, etc. In the optimal embodiment of the present invention, specifically, as the protective film 30, the most widely used methyl silicone oil (also called dimethyl silicone oil, and its chemical formula is (CH3)3SiO[(CH3)2SiO]n·Si(CH3)3) is adopted. Methyl silicone oil is a colorless and transparent novel synthetic polymer material, has a variety of different viscosities, and can select a viscosity in the range of 5 cps to 8 million cps as the viscosity range. Its form can be a very fluid liquid form or a thick semi-solid form. Methyl silicone oil has good water repellency, chemical stability, excellent electrical insulation, and high and low temperature resistance. It has a high flash point, a low freezing point, can be used long-term at -50°C to +200°C, has a small temperature-dependent viscosity coefficient, a large compression ratio, a low surface tension, high water and moisture repellency, and a small specific heat thermal conductivity. These characteristics together embody excellent protection characteristics for the multilayer ceramic capacitor 100.After applying a layer of insulating chemical material layer (specifically, a methyl silicone oil layer is adopted to form the protective film 30 in this embodiment) on the surface of the capacitor body 10 of the multilayer ceramic capacitor 100 by dipping, heat treatment is performed at 250 - 300 °C, and the insulating chemical material layer penetrates into the gaps formed on the surface after the capacitor body 10 is sintered, and further a layer of semi-permanent protective film 30 with excellent waterproofness, antifungal property, insulation, high temperature resistance and stability is formed.

[0052] Step 3: In order to facilitate the modification treatment and roughening treatment of the capacitor body 10 in the corresponding area, the protective film 30 in the area of the part where the external electrode 20 is formed is processed and removed by a laser device. For details, please refer to FIG. 6. In other embodiments, Step 3 may be performed simultaneously with the subsequent surface roughening treatment, that is, after the surface roughening treatment, the part of the protective film 30 corresponding to the capacitor body 10 where the external electrode 20 is provided is removed, and the part of the protective film 30 corresponding to the capacitor body 10 where the external electrode 20 is not provided is left.

[0053] Step 4: Using the methods of sandblasting, laser beam irradiation or heating by a laser irradiation device, the part of the capacitor body 10 where the external electrode 20 is formed is processed, and while denaturing the outer surface of the corresponding part of the capacitor body 10, a surface roughening treatment is performed to form a surface roughening layer 29 with an uneven surface. The depth of the surface roughening layer 29 is about 1um, and the adsorption capacity of the outer surface of the capacitor body 10 is improved, which is for the This helps to increase the contact area and strengthen the bonding force of the electrode metal layer 27 to the capacitor body 10. For details, please refer to FIG. 6. Since the first internal electrode 151 and the second internal electrode 153 are made of a metal material, the portions exposed from the end faces 13 of the first internal electrode 151 and the second internal electrode 153 are not roughened, while the portion of the dielectric layer 14 is roughened. It is understood that the roughness of the surface roughened layer 29 is greater than the roughness of the outer surface of the capacitor body 10 where the external electrode 20 is not provided. Since it is not roughened, the exposed portions or outer edges of the first internal electrode 151 and the second internal electrode 153 do not protrude from the surface roughened layer 29, that is, the first internal electrode 151 and the second internal electrode 153 are not lower than the most protruding part on the uneven surface of the surface roughened layer 29. In this way, it becomes easy to directly connect the electrode metal layer 27 of the external electrode 20 to the first internal electrode 151 and the second internal electrode 153 later. In order to more preferably perform the surface roughening treatment on the dielectric layer 14, a laser irradiation device for performing the processing can be appropriately selected according to the type of material used for the dielectric layer 14.

[0054] Step 5: Immerse the capacitor body 10 having the surface roughened layer 29 after the modification treatment and the roughening treatment in an activating chemical solution to perform a surface activation treatment, so as to further improve the adsorption ability of the capacitor body 10 to the ion catalyst. The activating chemical solution may be a solution suitable for the surface activation treatment of the dielectric layer 14, such as an aqueous sodium hydroxide solution.

[0055] Step 6: Immerse the capacitor body 10 in a solution of an ion catalyst containing at least one seed metal ion 31 of gold, silver, or a platinum group metal (for example, metals such as ruthenium, rhodium, palladium, osmium, iridium, and platinum), and adsorb the seed metal ion 31 in the ion catalyst onto the surface roughened layer 29 after the modification treatment and roughening treatment. For details, refer to FIG. 8. Although there is seed metal ion 31 on the exposed portion from the end face 13 of the internal electrode, which is the outer surface portion where the modification treatment and roughening treatment have not been performed, and on the outer surface of the protective film 30, it is understood that the seed metal ion 31 is not firmly adsorbed. In this embodiment, the ion catalyst is preferably an ion catalyst containing palladium ions.

[0056] Step 7: Wash the capacitor body 10 to wash off the seed metal ion 31 adhering to the exposed portion from the end face 13 of the internal electrode, which is the outer surface portion where the modification treatment and roughening treatment have not been performed, and the outer surface of the protective film 30. Immerse the capacitor body 10 in a reducing chemical solution to reduce the adsorbed ion catalyst to a seed metal 310 (catalyst metal). Since the ion catalyst is firmly fixed to the surface roughened layer 29 after the roughening treatment as described above, the reduced seed metal 310 will also be firmly fixed to the surface roughened layer 29. For details, refer to FIG. 9. It is understood that the seed metal 310 is not fixed to the outer surface of the capacitor body 10 where the roughening treatment has not been performed (the exposed portion from the end face 13 of the internal electrode 20 and the outer surface of the protective film 30). In this embodiment, since the ion catalyst specifically contains palladium ions, when the capacitor body 10 is immersed in the reducing chemical solution, the ion catalyst containing palladium ions is reduced to palladium metal, that is, the seed metal 310, and the palladium metal is firmly fixed to the surface roughened layer 29. Further, step 7 may include the step of immersing the capacitor body 10 on which the seed metal 310 is adsorbed in an aqueous solution containing a surfactant. In this way, the oxide layer on the outer surface of the adsorbed seed metal 310 (specifically, palladium metal in this embodiment) can be removed and activated, promoting the progress of the subsequent chemical plating process of the electrode metal layer 27.

[0057] Step 8: Immerse the capacitor body 10 in the electrode metal solution. Use the seed metal 310 on the outer surface of the capacitor body 10 as the seed layer 26 (or also called the catalyst layer). Also, since the portions exposed from the end faces 13 of the first internal electrode 151 and the second internal electrode 153 are made of a metal material, the electrode metal in the electrode metal solution precipitates and is plated on the seed layer 26 and the portions exposed from the end faces 13 of the first internal electrode 151 and the second internal electrode 153 to form the electrode metal layer 27. Also, since the electrode metal replaces the seed metal 310, a small amount of seed metal 310 remains on the capacitor body 10, and the electrode metal layer 27 is directly in contact with and connected to the portions exposed from the end faces 13 of the first internal electrode 151 and the second internal electrode 153. That is, the electrode metal layer 27 of the external electrode 20 is directly electrically connected to the first internal electrode 151 and the second internal electrode 153, improving the conductive performance. For details, refer to FIG. 10. Since the boundary edge 25 of the electrode metal layer 27 is connected to and shielded by the remaining protective film 30, it prevents moisture from seeping from the boundary edge 25 into the external electrode 20. In this embodiment, the electrode metal solution is a chemical copper plating solution, the seed metal 310 on the outer surface of the capacitor body 10 is palladium metal, and due to the palladium metal seed layer 26 (or catalyst layer), the copper metal in the chemical copper plating solution precipitates and is plated on the palladium metal, the first internal electrode 151 and the second internal electrode 153. Also, since the copper metal replaces the palladium metal, only a small amount of palladium metal remains on the capacitor body 10, and the copper metal layer becomes the electrode metal layer 27 of the external electrode 20. The thickness of the copper metal layer of the electrode metal layer 27 can be as thin as 0.5 - 0.6 um in the thinnest case, and can be up to 7 - 8 um in the case of the highest chemical plating efficiency. When the thickness exceeds 10 um, the chemical plating efficiency deteriorates. In other embodiments, when it is necessary to further increase the thickness of the electrode metal layer 27, if necessary, further chemical plating or electroplating can be performed to achieve a thickness of 10 - 15 um or higher to thicken the electrode metal layer 27. The electrode metal layer 27 has a uniform thickness, and there is no phenomenon that the thickness is thin at the edge of the end face 13 of the electrode metal layer 27 but thick at the end, and the stress is uniformly dispersed, preventing cracks from occurring in the external electrode 20.

[0058] Step 9: A protective layer 33 made of a metal material may be further formed on the outer surface of the electrode metal layer 27 by chemical plating or electroplating. The protective layer 33 can prevent oxidation of the electrode metal layer 27 and penetration of the welding metal layer 28. For details, please refer to FIG. 11. In the embodiment, the specific protective layer 33 is a nickel metal layer protective layer 33, and the thickness of the metal protective layer 33 formed by chemical plating is 2 - 5 μm.

[0059] Step 10: In order to facilitate welding of the external electrode 20 of the multilayer ceramic capacitor 100, a welding metal layer 28 is further formed on the outer surface of the protective layer 33 by chemical plating or electroplating. For details, please refer to FIGS. 12 and 13. It is understood that FIGS. 12 and 13 do not conflict with FIGS. 3 and 4, and FIGS. 12 and 13 are schematic diagrams in the forming step, which can make the means of the present invention more clearly understood. In the embodiment, the specific welding metal layer 28 is a tin metal layer welding metal layer, and the thickness of the welding metal layer 28 formed by chemical plating is 2 - 5 μm.

[0060] In the forming method of the multilayer ceramic capacitor 100 of the present invention, it is understood that step 1 is a cleaning step, steps 2 and 3 are treatment steps of the protective film 30, step 4 is a roughening treatment step, and step 5 is an activation step. In other embodiments of the present invention, any combination of step 1, steps 2 and 3, and step 5 may be selectively omitted, and the roughening treatment of step 4 and the ion catalyst solution immersion process of step 6 may be directly performed.

[0061] In the forming method of the multilayer ceramic capacitor 100 of the present invention, it is understood that step 9 is a forming step of the protective layer 33. In other embodiments of the present invention, step 9 may be selectively omitted, and the forming step of the welding metal layer 28 of step 10 may be directly performed.

[0062] The external electrodes of the multilayer ceramic capacitor 100 of the present invention include a seed layer 26 and an electrode layer from the inside to the outside, and the electrode layer includes a structure of at least two layers of at least an electrode metal layer 27 and a welding metal layer 28. The seed layer 26 can facilitate the plating formation of the electrode metal layer 27. The thickness after formation can be 7 - 8 μm, and in the thinnest case, it can be 0.5 - 0.6 μm. Also, when the seed metal 310 of the seed layer 26 is replaced with the electrode metal in the electrode metal solution, the seed metal 310 of the seed layer 26 decreases to a certain extent, and only a small amount of the seed metal 310 remains. Furthermore, by using the forming method in which the seed layer 26 replaces and forms the external electrode 20 of the electrode metal layer 27, the thickness of the external electrode 20 can be significantly reduced, and furthermore, the outer size of the multilayer ceramic capacitor 100 can be reduced. Also, after the electrode metal layer 27 (for example, a copper metal layer) formed by the chemical plating method is formed, it is uniformly distributed on the capacitor body 10. The thickness distribution on the end face 13 and the outer peripheral face 11 of the electrode metal layer 27 is uniform, and stress does not concentrate on the end face 13. Therefore, it is possible to prevent cracks from occurring in the external electrode 20 and cracks from occurring inside the capacitor body 10. The electrode metal layer 27 (for example, a copper metal layer) formed by plating (formed by the chemical plating method) has high density and can effectively prevent moisture and the penetration of the subsequent welding metal solution for plating formation between the external electrode 20 and the capacitor body 10. Furthermore, it is possible to avoid cracks from occurring inside the capacitor body 10 and improve the performance and lifespan of the product. The seed metal 310 of the seed layer 26 decreases to a certain extent, and only a small amount of the seed metal 310 remains. Furthermore, by using the forming method in which the seed layer 26 replaces and forms the external electrode 20 of the electrode metal layer 27, the thickness of the external electrode 20 can be significantly reduced, and furthermore, the outer size of the multilayer ceramic capacitor 100 can be reduced. Also, after the electrode metal layer 27 (for example, a copper metal layer) formed by the chemical plating method is formed, it is uniformly distributed on the capacitor body 10. The thickness distribution on the end face 13 and the outer peripheral face 11 of the electrode metal layer 27 is uniform, and stress does not concentrate on the end face 13. Therefore, it is possible to prevent cracks from occurring in the external electrode 20 and cracks from occurring inside the capacitor body 10. The electrode metal layer 27 (for example, a copper metal layer) formed by plating (formed by the chemical plating method) has high density and can effectively prevent moisture and the penetration of the subsequent welding metal solution for plating formation between the external electrode 20 and the capacitor body 10. Furthermore, it is possible to avoid cracks from occurring inside the capacitor body 10 and improve the performance and lifespan of the product.

[0063] In the present invention, the boundary edge 25 of the electrode metal layer 27 formed by the plating method on the upper and lower surfaces of the capacitor body 10 is linear in the width direction perpendicular to the longitudinal direction. Compared with the arc-shaped shrinkage rim formed by sintering in the prior art, the insulation distance L2 between the external electrodes 20 located at the two opposite ends can be increased, and furthermore, electrical interruption or short circuit between the external electrodes 20 can be prevented.

[0064] The present invention performs roughening treatment and modification treatment on the outer surface portion where the external electrode 20 is provided on the capacitor body 10 to form a surface roughened layer 29, thereby improving the adsorption ability of the seed layer 26 and the electrode metal layer 27 (for example, a copper metal layer) to the capacitor body 10, increasing the contact area for subsequent electroforming of the electrode metal layer 27 (for example, a copper metal layer), and improving the bonding ability between the electrode metal layer 27 (for example, a copper metal layer) and the capacitor body 10. The seed layer 26 can promote the stable and uniform adsorption of the subsequent electrode metal layer 27 (for example, a copper metal layer) to the capacitor body 10.

[0065] In the present invention, a protective film 30 is formed on the outer surface portion of the capacitor body 10 where the external electrode 20 is not formed. The specific thickness of the protective film 30 is equal to or greater than the thickness of the electrode metal layer 27 (for example, a copper metal layer). In this way, the protective film 30 can shield the boundary edge 25 of the electrode metal layer 27 (for example, a copper metal layer) and prevent moisture and subsequent welding metal solution from infiltrating from the boundary edge 25 of the electrode metal layer 27.

[0066] The technical features of the above embodiments can be arbitrarily combined. For the sake of simplicity of description, not all possible combinations of the technical features in the above embodiments are listed. However, as long as the combinations of these technical features do not conflict, they should be included within the scope described in this specification.

[0067] The above embodiments only represent the embodiments of the present invention and are described specifically and in detail. However, it should not be understood that the scope of the claims of the present invention is limited thereby. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and it should be pointed out that all of these are included in the protection scope of the present invention. Therefore, the protection scope of the present invention should follow the appended claims.

Explanation of Reference Numerals

[0068] 100 multilayer ceramic capacitor, 10 capacitor body, 11 outer peripheral surface, 13 end face, 14 dielectric layer, 151 first internal electrode, 153 second internal electrode, 30 protective film, 20 external electrode, 21 end wall, 23 peripheral wall, 25 boundary edge, 26 seed layer, 27 electrode metal layer, 28 welding metal layer, 29 surface roughening layer, 31 seed metal ions, 33 protective layer, 310 seed metal.

Claims

1. A multilayer ceramic capacitor including a capacitor body and two external electrodes provided on the capacitor body and facing each other with a space therebetween, wherein the capacitor body includes a plurality of first internal electrodes, a plurality of second internal electrodes, and a dielectric layer separating the first internal electrodes and the second internal electrodes, and one end of each of the first internal electrodes and the second internal electrodes is exposed from the outer surface of the capacitor body and electrically connected to the two external electrodes corresponding thereto. In the multilayer ceramic capacitor, the external electrode includes a seed layer and an electrode layer in order from the inside to the outside, the seed layer covers the outer surface of the portion of the capacitor body where the external electrode is provided, the outer surface of the capacitor body where the seed layer is provided is roughened to form a surface roughened layer having an uneven surface, and the electrode layer includes at least an electrode metal layer formed on the surface of the seed layer by plating and a welding metal layer formed by plating and located outside the electrode metal layer. A multilayer ceramic capacitor characterized by this.

2. The multilayer ceramic capacitor according to claim 1, wherein the first internal electrode and the second internal electrode are exposed from the seed layer and directly connected to the electrode metal layer.

3. The multilayer ceramic capacitor according to claim 1, wherein the seed layer includes at least one seed metal of at least gold, silver, or platinum group metals.

4. The multilayer ceramic capacitor according to claim 3, wherein the surface roughened layer has a roughness greater than the roughness of the outer surface of the portion of the capacitor body where the external electrode is not provided, and the seed metal of the seed layer is dispersed and distributed in the surface roughened layer at intervals.

5. The multilayer ceramic capacitor according to claim 1, wherein the electrode metal layer is formed on the outer surface of the seed layer by a chemical plating method.

6. The multilayer ceramic capacitor according to claim 4, wherein the portions of the first internal electrode and the second internal electrode exposed from the outer surface of the capacitor body are not roughened, and the first internal electrode and the second internal electrode are exposed from the surface roughened layer.

7. The multilayer ceramic capacitor according to claim 4, wherein the seed metal is palladium metal.

8. The electrode metal layer is a copper metal layer or a nickel metal layer, and the laminated ceramic capacitor according to claim 1 is characterized in that the thickness range of the electrode metal layer is 0.5 μm to 8 μm.

9. The laminated ceramic capacitor according to claim 6 is characterized in that the seed metal of the seed layer is replaced with an electrode metal solution to deposit the electrode metal layer, the seed metal is replaced and reduced, and the electrode metal layer is plated on the exposed portions from the outer surfaces of the surface roughened layers in the seed layer, the first internal electrode, and the second internal electrode.

10. The laminated ceramic capacitor according to claim 1 is characterized in that the electrode layer further includes a protective layer made of a metal material formed by chemical plating or electroplating on the outer surface of the electrode metal layer.

11. The laminated ceramic capacitor according to claim 10 is characterized in that the protective layer is a protective layer made of a nickel metal material.

12. The capacitor body includes two end faces facing each other in the longitudinal direction and an outer peripheral surface connecting the two end faces. The two external electrodes respectively cover the corresponding end faces and at least a part of the outer peripheral surface. One end of the first internal electrode and the second internal electrode is respectively exposed from the two end faces, and the edge of the electrode metal layer located on the outer peripheral surface forms a boundary edge extending linearly in the width direction perpendicular to the longitudinal direction. The laminated ceramic capacitor according to claim 1 is characterized by this.

13. The laminated ceramic capacitor according to claim 12 is characterized in that the outer peripheral surface of the capacitor body where the external electrode is not provided is covered with a layer of protective film, the thickness of the protective film is equal to or greater than the thickness of the electrode metal layer, and the protective film shields at least the boundary edge of the electrode metal layer.

14. The laminated ceramic capacitor according to claim 13 is characterized in that the protective film is formed of an insulating chemical material, and the insulating chemical material penetrates into the gaps formed after sintering of the capacitor body when heat-treated.

15. The laminated ceramic capacitor according to claim 14 is characterized in that the protective film is methyl silicone oil, and the thickness of the protective film is 0.3 - 5 μm.

16. A multilayer ceramic capacitor including a capacitor body and two external electrodes provided on the capacitor body and facing each other with a gap therebetween, wherein the capacitor body includes a plurality of first internal electrodes, a plurality of second internal electrodes, and a dielectric layer separating the first internal electrodes and the second internal electrodes, and one end of the first internal electrode and one end of the second internal electrode are respectively exposed from the outer surface of the capacitor body. In the manufacturing method of the multilayer ceramic capacitor, Step 1 of performing a surface roughening treatment on the outer surface of the portion of the capacitor body where the external electrode is provided to form a surface roughening layer having an uneven surface; Step 2 of immersing at least the outer surface of the capacitor body provided with the surface roughening layer in a solution of an ion catalyst containing at least one kind of seed metal ion of gold, silver, or platinum group metal, and adsorbing the seed metal ions in the ion catalyst on the outer surface of the surface roughening layer; Step 3 of immersing at least the outer surface of the capacitor body provided with the surface roughening layer in a reducing chemical solution to reduce the adsorbed seed metal ions to a seed metal, and fixing the reduced seed metal on the outer surface of the surface roughening layer to form a seed layer; Step 4 of plating the seed layer to form an electrode metal layer; Step 5 of plating outside the electrode metal layer to form a welding metal layer, characterized in that the manufacturing method of the multilayer ceramic capacitor includes the above steps.

17. After step 4 and before step 5, The method for manufacturing a multilayer ceramic capacitor according to claim 16 further includes a step of forming a protective layer made of a nickel metal layer with a thickness of 2 - 5 μm on the outer surface of the electrode metal layer by chemical plating or electroplating.

18. The welding metal layer is a tin metal layer formed by chemical plating or electroplating, and the thickness of the tin metal layer is 2 - 5 μm. The method for manufacturing a multilayer ceramic capacitor according to claim 16 is characterized in that.

19. In the plating method of step 4, at least the outer surface of the capacitor body provided with the surface roughening layer is immersed in an electrode metal solution, and the electrode metal in the electrode metal solution replaces a part of the seed metal, and the electrode metal is deposited and plated on the seed layer and the portions of the first internal electrode and the second internal electrode exposed from the outer surface of the capacitor body, and the electrode The method for manufacturing a multilayer ceramic capacitor according to claim 16, characterized in that a metal layer is formed.

20. The method for manufacturing a multilayer ceramic capacitor according to claim 16, characterized in that the surface roughening treatment is performed by a method such as sandblasting, laser beam irradiation, or heating.

21. After step 1 and before step 2, The method for manufacturing a multilayer ceramic capacitor according to claim 20, further comprising the step of immersing the surface roughened layer of the capacitor body in an activating chemical solution to perform a surface activation treatment, thereby improving the adsorption ability of the capacitor body to the ion catalyst.

22. Before step 1, The method for manufacturing a multilayer ceramic capacitor according to claim 16, further comprising a pretreatment step 2 of immersing the capacitor body in an insulating chemical solution and coating the entire outer surface of the capacitor body with a single layer of protective film formed of an insulating chemical material.

23. The method for manufacturing a multilayer ceramic capacitor according to claim 22, characterized in that when the protective film is heat-treated, the insulating chemical material in the protective film penetrates into the gaps formed on the outer surface of the capacitor body after sintering.

24. The method for manufacturing a multilayer ceramic capacitor according to claim 22, characterized in that the protective film is made of methyl silicone oil material.

25. After the surface roughening treatment, the portion of the protective film corresponding to the location where the external electrode of the capacitor body is provided is removed, and the portion of the protective film corresponding to the location where the external electrode of the capacitor body is not provided is left. The method for manufacturing a multilayer ceramic capacitor according to claim 22 is characterized by this.

26. Before the pretreatment step 2, The method for manufacturing a multilayer ceramic capacitor according to claim 22, further comprising a pretreatment step 1 of performing a cleaning treatment on the entire capacitor body.

27. After step 2 and before step 3, The method for manufacturing a multilayer ceramic capacitor according to claim 22, further comprising the step of performing a cleaning treatment on the capacitor body to wash away the seed metal ions adhering to the outer surfaces of the first internal electrode, the second internal electrode, and the protective film.

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