A manufacturing method of a multilayer ceramic capacitor

Abstract

The present invention discloses a manufacturing method of a multilayer ceramic capacitor, which relates to the technical field of multilayer ceramic capacitors and includes the following operating steps: depositing a dielectric layer and an inner electrode on the film surface in a cycle, with the last layer being the dielectric layer, to obtain a multilayer ceramic capacitor A; dicing and cutting the multilayer ceramic capacitor A to remove the film, obtaining small multilayer ceramic capacitors A; selectively etching both ends of the inner electrodes in the small multilayer ceramic capacitors A to obtain small multilayer ceramic capacitors B; applying an insulating layer slurry on their outer surfaces and sintering at a low temperature to obtain small multilayer ceramic capacitors C; grinding the insulating layer at the positions of the metal outer electrodes of the small multilayer ceramic capacitors C, applying a conductive slurry on the exposed inner electrodes, and sintering at a low temperature to obtain small multilayer ceramic capacitors D; nickel-plating the metal outer electrodes of the small multilayer ceramic capacitors D to obtain the product.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic capacitors, and specifically to a manufacturing method of a multilayer ceramic capacitor. Background Art

[0002] Multilayer ceramic capacitors (MLCCs) are one of the most widely used chip components in the world; their unique laminated structure gives them the characteristics of small size and large specific capacitance; as an important part of pulse power technology, dielectric ceramic capacitors are widely used in devices due to their extremely fast charge and discharge speeds and ultra-high power densities; pulsed dielectric ceramic capacitors are commonly used in lasers, electron beams, plasma emitters, and pulse power equipment due to their high power densities; at the same time, compared with organic energy storage materials, dielectric ceramic capacitors can operate normally at higher temperatures and perform well in fields such as hybrid electric vehicles, electromagnetic weapons, and underground exploration equipment; there is a magnetoelectric coupling phenomenon in some dielectric materials, that is, the interaction between polarization and magnetic field, so it has been widely used in electronic engineering.

[0003] The structure of MLCC mainly includes three major parts: dielectric layer, inner electrode, and outer electrode; currently, most MLCCs transfer the inner electrode paste to the dielectric layer by screen printing, and the inner electrode is made after lamination, cutting, and sintering. The inner electrode made in this way has a high cost, and replacing the palladium-containing noble metal inner electrode with base metals such as nickel or copper to reduce the production cost of high-performance MLCCs has become one of the main trends in the development of ceramic capacitor technology; at the same time, with the market demand for thinner and more complete terminal devices, it promotes the development of MLCCs towards miniaturization and small size.

[0004] At the same time, the inner electrode material needs to have a high melting point to prevent melting or deformation during the high-temperature sintering process of MLCC; based on the above considerations, the present invention proposes a method for preparing a thin and light MLCC with copper and silver as inner electrodes by physical vapor deposition technology. Summary of the Invention

[0005] The purpose of the present invention is to provide a manufacturing method of a multilayer ceramic capacitor to solve the problems raised in the prior art.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A manufacturing method of a multilayer ceramic capacitor includes the following operating steps:

[0008] S1: Cyclically deposit a dielectric layer and an inner electrode on the surface of the film, and the last layer is the dielectric layer to obtain a multilayer ceramic capacitor A;

[0009] S2: Perform scribing and cutting on the multilayer ceramic capacitor A to remove the film and obtain small multilayer ceramic capacitors A;

[0010] S3: Selectively etch both ends of the inner electrodes in the small multi-layer ceramic capacitor A to obtain the small multi-layer ceramic capacitor B;

[0011] S4: Apply an insulating layer slurry on the outer surface of the small multi-layer ceramic capacitor B and sinter it at 300 - 500 °C to obtain the insulating layer; this is the small multi-layer ceramic capacitor C;

[0012] S5: Grind off the insulating layer at the position of the metal outer electrode of the small multi-layer ceramic capacitor C, apply a conductive paste on the exposed inner electrode, and sinter it at a low temperature of 80 - 120 °C to obtain the metal outer electrode layer, which is the small multi-layer ceramic capacitor D;

[0013] S6: Immerse the metal outer electrode of the small multi-layer ceramic capacitor D in a nickel plating solution at 85 - 95 °C for nickel plating treatment, wash it with pure water to remove the residual chemical solution, and dry the moisture with hot air to obtain the product.

[0014] In the solution, in the process of S5, use a double-sided surface grinding machine to grind off the insulating layer at the outer electrode position of the small multi-layer ceramic capacitor C after sintering the insulating layer slurry on the outer surface. During grinding, set a number of workpiece positions evenly on the planetary wheel according to the radial dimension of the small multi-layer ceramic capacitor C, insert the small multi-layer ceramic capacitor C into the workpiece positions, and make the upper and lower end faces contact with the upper and lower grinding disks of the double-sided surface grinding machine respectively. As the upper and lower grinding disks rotate, under the combined action of the abrasive, grind off the insulating layer at the end electrode; as Figure 4 shown, where the thickness T of the planetary wheel should satisfy: A < T < B. During grinding, it should be noted that on the Cu electrode side, the Ag should not be exposed, and on the Ag electrode side, the Cu should not be exposed.

[0015] Preferably, the single-layer thickness of the dielectric layer is 5 - 7 μm, and the single-layer thickness of the inner electrode is 1.0 - 1.2 μm.

[0016] Preferably, the thin film includes one of PTFE, FEP, and ETFE; the dielectric layer includes one of silicon nitride and barium carbonate.

[0017] Preferably, the inner electrode layer is one of Cu and Ag; the method of selective etching is: immerse one end of the inner electrode in the small multi-layer ceramic capacitor A in the Ag etching solution for etching, take it out, and wash it with pure water to remove the residual etching solution; then immerse the other end of its inner electrode in the Cu etching solution for etching, take it out, and wash it with pure water to remove the residual etching solution.

[0018] Preferably, the Ag etchant is: 25 g / L silver nitrate, 50 g / L copper nitrate, 250 mL / L of 65 wt% nitric acid solution; the Cu etchant is a hydrogen peroxide-based etchant or a ferric chloride-based etchant, and the etching rate is 1.1 μm / min;

[0019] The hydrogen peroxide-based etchant comprises the following components: 150 - 155 g / L of concentrated sulfuric acid, 10 - 12 mL / L of phenol sulfonic acid, 25 - 30 g / L of hydrogen peroxide; the ferric chloride-based etchant comprises the following components: 0.70 - 0.75 g / mL of ferric chloride, 0.02 - 0.03 g / mL of hydrochloric acid.

[0020] In the solution, during film deposition, the deposition sequence is dielectric layer - Cu - dielectric layer - Ag - dielectric layer - Cu - dielectric layer - Ag -... - dielectric layer;

[0021] In S4, selective etching is performed on two different metal inner electrodes respectively, that is, only Ag is etched at one end while Cu is retained; only Cu is etched at the other end while Ag is retained; when etching Cu at one end, the Cu at the other end is protected; when etching Ag at one end, the Ag at the other end is protected; and when etching Cu, it is ensured that there is no influence on Ag, and when etching Ag, it is ensured that there is no influence on Cu.

[0022] In the solution, the hydrogen peroxide-based etchant is prepared and used immediately, and care should be taken to avoid direct sunlight to prevent the decomposition of hydrogen peroxide, which may lead to a decrease in etching ability; the higher the concentration of silver nitrate, the more obvious the etching effect; the addition of copper nitrate can enhance the etching rate and etching depth.

[0023] Preferably, the preparation method of the insulating layer paste is as follows: uniformly mix insulating powder and glass powder to obtain a solid mixture; add a binder to a solvent and mix uniformly to obtain a resin solution; add the resin solution to the solid mixture, and then add an auxiliary agent and mix uniformly to obtain the insulating layer paste;

[0024] The insulating layer paste comprises the following components: 70 - 85 wt% of insulating powder, 5 - 15 wt% of binder, 1 - 5 wt% of glass powder, 3 - 10 wt% of solvent, 0.5 - 3 wt% of auxiliary agent;

[0025] The insulating powder includes one or more of ceramic powder and polymer powder;

[0026] The binder includes one or more of epoxy resin, phenolic resin, and acrylic resin;

[0027] The glass powder includes one or more of Bi2O3, B2O3, PbO, and ZnO;

[0028] The solvent includes one of alcohols, esters, and ketones; the auxiliary agents include a dispersant and a thixotropic agent.

[0029] In the solution, the small multi-layer ceramic capacitor C coated with the insulating layer paste is sintered at a low temperature to form a dense bond between the particles and form the insulating layer.

[0030] More preferably, the preparation method of the conductive paste is as follows: adding a polymer resin to a solvent, mixing evenly, and completely dissolving the polymer resin at 80 ± 1 °C; adding an additive and continuing to stir, filtering to remove impurities to obtain an organic carrier; adding conductive silver powder to the organic carrier, ball-milling and mixing, then performing vacuum degassing for 3 to 10 minutes, and rolling and grinding 2 to 4 times to obtain the conductive paste;

[0031] The conductive paste includes the following components: 45 to 70 wt% of conductive silver powder, 8 to 13 wt% of polymer resin, 2 to 7 wt% of additive, and 20 to 35 wt% of solvent;

[0032] The polymer resin includes one or more of polyvinyl acetate and polyamide;

[0033] The additive includes one or two of castor oil and tributyl phosphate;

[0034] The solvent includes one or two of diethylene glycol ethyl ether acetate and dimethyl nylonate.

[0035] More preferably, the average particle size of the conductive silver powder is 5 to 10 μm; the vacuum degree of the vacuum degassing is 0.08 to 0.12 MPa, and the degassing time is 3 to 10 minutes.

[0036] More preferably, the nickel plating solution includes the following components: 25 to 30 g / L of nickel sulfate, 8 to 10 g / L of sodium acetate, 8 to 10 g / L of sodium phosphite pentahydrate, and the pH of the nickel plating solution is 4 to 6.

[0037] In the solution, the additives castor oil and tributyl phosphate used mainly play the role of increasing the plasticity and leveling property of the paste. Description of the Drawings

[0038] Figure 1 It is a schematic diagram of the structure after multiple cyclic depositions on the thin film;

[0039] Figure 2 It is a schematic diagram after selective etching of Ag;

[0040] Figure 3 It is a schematic diagram after selective etching of Cu;

[0041] Figure 4 It is a schematic diagram after low-temperature sintering of the applied insulating layer paste;

[0042] Figure 5 It is a schematic diagram after removing the insulating layer;

[0043] Figure 6 It is a schematic diagram after plating Ni on the outer electrode. Specific embodiments

[0044] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0045] Embodiment: As Figures 1 to 6 shown, the present invention provides a technical solution for a manufacturing method of a multilayer ceramic capacitor, including the following operating steps;

[0046] S1: Paste a layer of film on the fixture in the physical vapor deposition chamber; deposit dielectric layers (Si3N4), inner electrodes (Cu), dielectric layers (Si3N4), inner electrodes (Ag) on the film surface through magnetron sputtering in multiple cycles, and the last layer is the dielectric layer to obtain a multilayer ceramic capacitor A;

[0047] S2: Use a precision dicing machine to dice the multilayer ceramic capacitor A according to the target size at a cutting speed of 4 mm / s, and remove the film after cutting to obtain small multilayer ceramic capacitors A;

[0048] S3: Immerse one end of the inner electrode in the small multilayer ceramic capacitor A into the Ag etching solution for etching, take it out, and wash it with pure water to remove the residual etching solution, as Figure 2 shown; then immerse the other end of its inner electrode into the Cu etching solution for etching, take it out, and wash it with pure water to remove the residual etching solution, as Figure 3 shown to obtain small multilayer ceramic capacitors B;

[0049] Among them, the Cu etching includes the following components: 155 g / L of concentrated sulfuric acid, 30 g / L of hydrogen peroxide, and 12 mL / L of phenolsulfonic acid;

[0050] Preparation of the Ag etching solution: Add 5 g of silver nitrate to 50 mL of distilled water, stir until completely dissolved, add 10 g of copper nitrate to 150 mL of distilled water, stir until completely dissolved; mix the above two solutions and stir well, add 50 mL of nitric acid with a concentration of 65%, mix evenly until completely dissolved, and then filter to remove the impurities therein to obtain the Ag etching solution;

[0051] S4: Apply the insulating layer paste on the outer surface of the small multi-layer ceramic capacitor B and sinter it at 300 °C to obtain the insulating layer; this is the small multi-layer ceramic capacitor C, as Figure 4 shown;

[0052] Among them, the insulating layer paste includes the following components: 70 wt% alumina powder, 15 wt% epoxy resin, 5 wt% Bi2O3, 7 wt% ethanol, 3 wt% dispersant;

[0053] S5: Grind off the insulating layer at the position of the metal outer electrode of the small multi-layer ceramic capacitor C, as Figure 5 shown; and apply the conductive paste on the exposed inner electrode and sinter it at a low temperature of 90 °C to obtain the metal outer electrode layer, which is the small multi-layer ceramic capacitor D;

[0054] S6: Immerse the metal outer electrode of the small multi-layer ceramic capacitor D in a nickel plating solution (pH = 6) at 90 °C for nickel plating treatment, wash it with pure water to remove the residual chemical solution, and dry the moisture with hot air to obtain the product, as Figure 6 shown;

[0055] Among them, the nickel plating solution includes the following components: 30 g / L nickel sulfate, 10 g / L sodium acetate, 10 g / L sodium hypophosphite pentahydrate.

[0056] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be encompassed within the present invention. Any reference signs in the claims should not be regarded as limiting the claims involved.

Claims

1. A manufacturing method of a multilayer ceramic capacitor, characterized in that: It includes the following operation steps: S1: Cyclically deposit a dielectric layer and inner electrodes on the surface of the thin film, with the last layer being the dielectric layer, to obtain a multi-layer ceramic capacitor A; S2: Perform scribing and cutting on the multi-layer ceramic capacitor A to remove the thin film, obtaining small multi-layer ceramic capacitors A; S3: Selectively etch both ends of the inner electrodes in the small multi-layer ceramic capacitors A to obtain small multi-layer ceramic capacitors B; S4: Apply an insulating layer slurry on the outer surface of the small multi-layer ceramic capacitors B and sinter at 300°C to 500°C to obtain an insulating layer; That is, small multi-layer ceramic capacitors C; S5: Grind off the insulating layer at the position of the metal outer electrodes of the small multi-layer ceramic capacitors C, apply a conductive paste on the exposed inner electrodes, and perform low-temperature sintering at 80 - 120°C to obtain metal outer electrodes, which are small multi-layer ceramic capacitors D; S6: Immerse the metal outer electrodes of the small multi-layer ceramic capacitors D in a nickel plating solution at 85 - 95°C for nickel plating treatment to obtain the product.

2. The manufacturing method of a multi-layer ceramic capacitor according to claim 1, wherein: The single-layer thickness of the dielectric layer is 5 - 7 μm, and the single-layer thickness of the inner electrode is 1.0 - 1.2 μm.

3. The manufacturing method of a multi-layer ceramic capacitor according to claim 1, characterized in that: The thin film is one of PTFE, FEP, and ETFE; the dielectric layer is one of silicon nitride and barium carbonate.

4. The manufacturing method of a multi-layer ceramic capacitor according to claim 1, characterized in that: The inner electrode is one of Cu and Ag; the method of selective etching is as follows: One end of the inner electrode in the small multi-layer ceramic capacitor A is immersed in an Ag etching solution for etching, taken out, and rinsed with pure water to remove the residual etching solution; then the other end of its inner electrode is immersed in a Cu etching solution for etching, taken out, and rinsed with pure water to remove the residual etching solution.

5. The manufacturing method of a multi-layer ceramic capacitor according to claim 4, characterized in that: The Ag etching solution is: 25 g / L silver nitrate, 50 g / L copper nitrate, and 250 mL / L of 65 wt% nitric acid solution; the Cu etching solution is a hydrogen peroxide type etching solution or a ferric chloride type etching solution, and the etching rate is 1.1 μm / min; The hydrogen peroxide type etching solution includes the following components: 150 - 155 g / L of concentrated sulfuric acid, 10 - 12 mL / L of phenol sulfonic acid, and 25 - 30 g / L of hydrogen peroxide; the ferric chloride type etching solution includes the following components: 0.70 - 0.75 g / mL of ferric chloride, 0.02 - 0.03 g / mL of hydrochloric acid.

6. The manufacturing method of a multi-layer ceramic capacitor according to claim 1, characterized in that: The preparation method of the insulating layer slurry is as follows: Uniformly mix insulating powder and glass powder to obtain a solid mixture; add a binder to a solvent and uniformly mix to obtain a resin solution; Add the resin solution to the solid mixture, and then add an auxiliary agent and uniformly mix to obtain the insulating layer slurry; The insulating layer slurry includes the following components: 70 - 85 wt% of insulating powder, 5 - 15 wt% of binder, 1 - 5 wt% of glass powder, 3 - 10 wt% of solvent, 0.5 - 3 wt% of auxiliary agent; The insulating powder includes one or more of ceramic powder and polymer powder; The binder includes one or more of epoxy resin, phenolic resin, and acrylic resin; The glass powder includes one or more of Bi2O3, B2O3, PbO, and ZnO; The solvent includes one of alcohols, esters, and ketones; the auxiliary agent includes a dispersant and a thixotropic agent.

7. The manufacturing method of a multi-layer ceramic capacitor according to claim 1, characterized in that: The preparation method of the conductive paste is as follows: Add the polymer resin into the solvent, mix evenly, and completely dissolve the polymer resin at 80±1°C; then add the additive and continue stirring, filter to remove impurities to obtain the organic carrier; add the conductive silver powder into the organic carrier, mix by ball milling, then perform vacuum degassing for 3 to 10 minutes, and then roll and mill 2 to 4 times to obtain the conductive paste; The conductive paste comprises the following components: 45 to 70 wt% of conductive silver powder, 8 to 13 wt% of polymer resin, 2 to 7 wt% of additive, and 20 to 35 wt% of solvent; The polymer resin includes one or more of polyvinyl acetate and polyamide; The additive includes one or both of castor oil and tributyl phosphate; The solvent includes one or both of diethylene glycol ethyl ether acetate and dimethyl adipate; 8. The manufacturing method of a multi-layer ceramic capacitor according to claim 7, characterized in that: The average particle size of the conductive silver powder is 5 to 10 μm; the vacuum degree of the vacuum degassing is 0.08 to 0.12 MPa, and the degassing time is 3 to 10 minutes.

9. The manufacturing method of a multi-layer ceramic capacitor according to claim 1, characterized in that: The nickel plating solution comprises the following components: 25 to 30 g / L of nickel sulfate, 8 to 10 g / L of sodium acetate, and 8 to 10 g / L of sodium phosphite pentahydrate; the pH of the nickel plating solution is 4 to 6.

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