A method for preparing a multilayer ceramic capacitor

Abstract

The present invention discloses a method for preparing a multilayer ceramic capacitor, comprising: preparing a ceramic sheet from a ceramic slurry on a carrier film; printing a conductive paste on the surface of the ceramic sheet to obtain a printed sheet; placing the printed sheet on a carrier device, placing a transfer device on the upper portion of the printed sheet, applying a magnetic field between the carrier device and the transfer device to peel off the printed sheet, and obtaining a green part; laminating the green part, pressing, cutting, debonding, sintering, and terminating to obtain the multilayer ceramic capacitor; the conductive paste contains 3 8wt% magnetic organic matter; the magnetic organic matter is at least one of a nitroxide free radical and an organic complex organic magnetic substance. The present invention converts the traditional vacuum adsorption force into a force controlled by a magnetic field by adding a magnetic organic matter to the conductive paste, thereby achieving more uniform force control between the printed sheet and the carrier film band, reducing problems such as deformation and damage of the printed sheet caused by uneven force during the peeling process, and achieving higher quality peeling.

Description

Technical Field

[0001] The present invention relates to the field of multilayer ceramic capacitors, and in particular to a method for preparing a multilayer ceramic capacitor. Background Art

[0002] With the increasing use of chip-type multilayer ceramic capacitors (MLCCs) in daily life, people hope to obtain small, thin, and reliable high-capacity MLCCs. In the MLCC preparation process, the dielectric layer is obtained by casting ceramic slurry on a carrier film tape, and then the internal electrode layer is obtained by screen printing on the dielectric layer. Finally, the dielectric layer printed with the internal electrode is peeled off from the PET film tape for lamination. Another process is to peel off the dielectric layer first, then print the electrodes after lamination until the required number of layers is reached. Both of these processes involve lamination and peeling steps. Therefore, improving the peeling quality and lamination accuracy is crucial to improving the reliability of MLCCs.

[0003] At present, the peeling process adopts the method of using vacuum adsorption in conjunction with a peeling plate to peel the printed sheet from the PET film. The vacuum adsorption heads are mainly distributed around the periphery and on the internal cross-path. On the one hand, vacuum adsorption requires that the adsorption holes are completely blocked by the adsorbed substance in order to apply force evenly, thereby preventing the printed sheet from moving during peeling. However, for the internal electrode with a certain thickness, when the adsorption holes are located at the electrode and the blank margin at the same time, due to the problem of step difference, the peeling process will cause varying degrees of damage to the printed sheet. In severe cases, it may even cause the printed sheet to deform, thereby affecting the lamination progress. In addition, the position of the undistributed adsorption holes is also inconsistent with the degree of deformation of the adsorption position, which greatly affects the subsequent lamination quality. On the other hand, when the adsorption holes have a small aperture, it is very easy to absorb impurities such as film fragments, resulting in hole blockage, further causing problems such as poor peeling. Regular cleaning is time-consuming and labor-intensive, greatly reducing production efficiency. Summary of the Invention

[0004] In order to overcome the defect of poor stripping effect in the existing multilayer ceramic capacitor stripping process, the object of the present invention is to provide a method for preparing a multilayer ceramic capacitor.

[0005] The present invention provides a method for preparing a multilayer ceramic capacitor, comprising the following steps:

[0006] 1) preparing a ceramic sheet by coating the ceramic slurry on a carrier film;

[0007] 2) printing a conductive paste on the surface of the ceramic sheet and drying it to obtain a printed sheet;

[0008] 3) placing the printed sheet on a carrier, placing a transfer device on top of the printed sheet, and applying a magnetic field between the carrier and the transfer device to peel off the printed sheet to obtain a green part;

[0009] 4) laminating the green parts, then pressing the laminated green parts, cutting, debinding, sintering, and terminating to produce the multilayer ceramic capacitor;

[0010] In step 2), the conductive paste contains 3-8 wt% of magnetic organic matter; the magnetic organic matter is at least one of a nitroxide free radical organic magnetic substance and an organic complex organic magnetic substance.

[0011] The carrying device described in the present invention is a conventional diaphragm carrying operating table in this field, such as a stacking table; the transfer device described in the present invention is a conventional mobile diaphragm facility in this field, such as a conveying table; the implementation of the technical solution of the present invention is not limited to specific stacking tables and conveying tables.

[0012] Preferably, in the preparation method of this multilayer ceramic capacitor, in step 1), the ceramic slurry comprises the following components in mass percentage: 40-60wt% of ceramic powder, 4-8wt% of binder, 0.2-0.4wt% of plasticizer, and 30-50wt% of organic solvent; further preferably, the ceramic slurry comprises the following components in mass percentage: 45-55wt% of ceramic powder, 4-6wt% of binder, 0.2-0.4wt% of plasticizer, and 40-46wt% of organic solvent; in some specific embodiments of the present invention, the binder comprises at least one of PVB (polyvinyl butyral), polystyrene, carboxymethyl cellulose, and acrylic resin; the organic solvent comprises at least one of toluene, ethanol, acetone, and isopropyl alcohol; and the plasticizer comprises at least one of dibutyl phthalate, tributyl citrate, phthalate, and hydrogenated rosin alcohol.

[0013] Preferably, in the method for preparing the multilayer ceramic capacitor, in step 1), the thickness of the ceramic sheet is 1-20 μm.

[0014] In step 1) of the present invention, the ceramic slurry may be formed into a ceramic sheet on a carrier film by a tape casting process.

[0015] Preferably, in the preparation method of this multilayer ceramic capacitor, in step 2), the conductive paste further includes the following components in mass percentage: 38-63wt% of conductive metal powder, 5-12wt% of ceramic powder, 0.5-2wt% of dispersant, 0.5-2wt% of plasticizer, and 30-50wt% of organic solvent; in some specific embodiments of the present invention, the conductive metal powder includes at least one of nickel powder, copper powder, gold powder, and silver powder; the plasticizer includes at least one of dibutyl phthalate, tributyl citrate, phthalate, and hydrogenated rosin alcohol; and the organic solvent includes at least one of toluene, ethanol, acetone, and isopropyl alcohol.

[0016] Preferably, in the method for preparing the multilayer ceramic capacitor, in step 2), the printing thickness of the conductive paste is 0.3-2 μm; further preferably, the printing thickness of the conductive paste is 1-2 μm.

[0017] Preferably, in the method for preparing the multilayer ceramic capacitor, in step 2), the nitroxide free radical organic magnetic substance includes nitroxide free radical substituted polydiacetylene; and the organic complex organic magnetic substance includes at least one of PANiCNQ and CsNiCr(CN)6·2H2O.

[0018] More preferably, the nitroxide-substituted polydiacetylene includes poly-1,4-bis(2,2,6,6-tetramethyl-4-hydroxy-1-oxypiperidinyl)diacetylene.

[0019] In the present invention, the structural formula of PANiCNQ is shown below:

[0020]

[0021] PANiCNQ is prepared from polyaniline (PANi) and 7,7,8,8-tetracyanoquinodimethane (TCNQ). The specific preparation method is referred to the existing literature "Room temperature magnetic order in an organic magnet derived from polyaniline", doi:10.1016 / j.polymer.2004.06.002.

[0022] In the present invention, the synthesis reaction formula of CsNiCr(CN)6·2H2O is:

[0023] NiCl2+K3[Cr(CN)6]+CsCl+2H2O=CsNi[Cr(CN)6]·2H2O+3KCl;

[0024] The specific preparation method of CsNiCr(CN)6·2H2O is referred to the existing literature "Generation and O2 Adsorption Studies of the Microporous Magnets CsNi[Cr(CN)6](T C =75K)and Cr3[Cr(CN)6]2·6H2O(T N =219K)》, doi:10.1021 / ja803926y.

[0025] Preferably, in the method for preparing the multilayer ceramic capacitor, in step 2), the conductive paste contains 3-8 wt % of magnetic organic matter; further preferably, the conductive paste contains 5-8 wt % of magnetic organic matter.

[0026] Preferably, in the preparation method of this multilayer ceramic capacitor, in step 3), the magnetic field strength is ≥0.1T; further preferably, the magnetic field strength is 0.1-10T; even further preferably, the magnetic field strength is 5-10T; the direction of the magnetic field is perpendicular to the diaphragm, and when the magnetic field is applied to the side of the diaphragm (non-vertical direction), it may lead to unsatisfactory peeling effect.

[0027] Preferably, in the method for preparing the multilayer ceramic capacitor, in step 4), the lamination process is carried out in a controllable magnetic field, and during lamination, the laminated parts and the sheets to be laminated are controlled to maintain opposite magnetic properties.

[0028] Preferably, in the method for preparing the multilayer ceramic capacitor, in step 4), the debinding is performed by heat treatment at a temperature of 250-350°C.

[0029] Preferably, in the preparation method of this multilayer ceramic capacitor, in step 4), the sintering treatment temperature is 900-1200°C, the sintering treatment time is 3-5h, and the sintering treatment is carried out under a reducing atmosphere, such as a reducing atmosphere composed of H2-N2-H2O gas.

[0030] Preferably, in the method for preparing the multilayer ceramic capacitor, in step 4), the termination is specifically: coating external electrodes on both end surfaces of the ceramic sintered body, and then performing an end sintering treatment at 750-850°C.

[0031] The beneficial effects of the present invention are:

[0032] The preparation method of the multilayer ceramic capacitor of the present invention converts the traditional vacuum adsorption force into a force controlled by a magnetic field by adding magnetic organic matter to the conductive paste, thereby achieving more uniform force control between the printed sheet and the carrier film tape, reducing problems such as deformation and damage of the printed sheet caused by uneven force during the peeling process, and ultimately achieving a higher quality peeling effect. The added magnetic organic matter is completely volatilized during the debinding and sintering processes and will not affect the performance of the MLCC. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of an operating table of the present invention. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below using specific examples. Unless otherwise specified, the raw materials, reagents, and apparatus used in the examples and comparative examples are available from conventional commercial sources or by conventional methods. Unless otherwise specified, all experimental or testing methods are conventional in the art.

[0035] Example 1

[0036] This embodiment provides a method for preparing a multilayer ceramic capacitor, which specifically includes the following steps:

[0037] S1: 50 wt% barium titanate ceramic powder, 5 wt% PVB adhesive, 0.3 wt% DOP, 44.7 wt% toluene, ethanol and isopropyl alcohol organic solvents (in a mass ratio of 1:1:1) were mixed evenly to prepare a ceramic slurry for later use.

[0038] S2: The ceramic slurry obtained in S1 is cast on a carrier PET film tape to obtain a ceramic green sheet with a smooth surface after drying. The thickness of the cast sheet is 10 μm.

[0039] S3: 49wt% nickel powder, 5wt% barium titanate ceramic powder, 0.5wt% oleoylsarcosine organic dispersant, 0.5wt% DOP plasticizer, 5wt% magnetic organic matter A (poly 1,4-bis(2,2,6,6-tetramethyl-4-hydroxy-1-oxyl piperidine) diacetylene), 40wt% toluene and anhydrous ethanol (mass ratio 1:1) mixed organic solvent are mixed in the proportions to prepare nickel paste for the inner electrode.

[0040] S4: Use the nickel paste in S3 to screen print on the ceramic green sheet to obtain a printed sheet with magnetic properties. The nickel paste printing thickness is 1 μm.

[0041] S5: Apply a magnetic field to the surface of the transport table to peel off the printed sheet. Set the magnetic field strength to 5T and the magnetic field direction to "+" (from top to bottom perpendicular to the film direction is marked as +; from bottom to top is marked as "-"). Under the action of the controllable magnetic field, the printed sheet is strongly attracted and adhered to it by magnetic force, completing the non-damaged peeling. Then, it is transported to the designated position. The printed sheet is separated from the transport table by removing the magnetic field (setting the magnetic field strength to 0T) or applying an opposite magnetic field ("-") force. When stacking, the stacked piece and the sheet to be stacked are always controlled to maintain opposite magnetic properties (such as Figure 1 ), the strong interaction force of the magnetic field makes the stacked layers tightly bonded until the required number of layers is reached.

[0042] S6: The stacked green bodies are hydrostatically pressed and cut, and the ceramic laminates are subjected to binder removal treatment at a temperature of 300°C in an air atmosphere. Then, they are fired at a firing temperature of 1100°C for about 4 hours in a reducing atmosphere composed of H2-N2-H2O gas. Conductive copper paste for external electrodes is applied to both end surfaces of the external ceramic sintered body, and the ends are fired at a temperature of 750°C to form external electrodes to obtain high-capacity MLCC products.

[0043] The transfer platform uses a controllable magnetic field, imbued with controllable direction and intensity. When the transfer platform contacts the printed sheet surface, it attracts the entire sheet through a strong magnetic force, ensuring a complete bond. Other areas, such as blank areas, are unaffected by the magnetic field, preventing deformation at non-bonded locations. This allows the peeling platform to achieve the desired separation of the printed sheet. During stacking, the use of an opposing magnetic field ensures precise positioning and tight bonding of the layers, significantly reducing defects caused by mechanical stacking offsets.

[0044] Examples 2-13 and Comparative Examples 1-15

[0045] Examples 2-13 and Comparative Examples 1-15 all provide a method for preparing a multilayer ceramic capacitor. The specific process parameters are shown in Table 1 below, wherein the process parameters not listed in Table 1 are the same as those in Example 1. Substance A in Table 1 is poly-1,4-bis(2,2,6,6-tetramethyl-4-hydroxy-1-oxyl piperidine) diacetylene (CAS No.: 14306-88-8); substance B is (PANiCNQ), and the preparation method is referenced to the existing literature "Room temperature magnetic order in an organic magnet derived from polyaniline", doi:10.1016 / j.polymer.2004.06.002; substance C is CsNi[Cr(CN)6]·2H2O, and the preparation method is referenced to the existing literature "Generation and O2Adsorption Studiesof the Microporous Magnets CsNi[Cr(CN)6](T C =75K)and Cr3[Cr(CN)6]2·6H2O(T N =219K)》, doi:10.1021 / ja803926y.

[0046] Comparative Examples 9 and 14 do not use an external magnetic field. Instead, step S5 of these examples utilizes a conventional vacuum adsorption method. The specific steps of this method are as follows: The transport platform uses cutting blades on its four sides to separate the printed sheet from the PET film. Simultaneously, the transport platform uses adsorption holes on its surface to hold the printed sheet. The peeling plate then begins to move, generating a peeling force that separates the printed sheet from the film. The subsequent lamination steps then proceed.

[0047] Table 1

[0048]

[0049]

[0050] Performance testing:

[0051] (1) Nickel slurry performance test:

[0052] The nickel slurries prepared in step S3 of the above embodiment and comparative example were subjected to performance tests. The test methods or instruments and the qualification standards are shown in Table 2 below.

[0053] Table 2

[0054]

[0055] (2) Magnetic strength performance test:

[0056] Test method: The strength performance is based on the value of the electrical signal applied by the conveyor. After the peeling process, an appearance inspection is carried out to determine whether the set magnetic strength meets the requirements for laminate peeling. If the printed sheet is not completely separated from the PET, the printed sheet is not tightly attached to the lower surface of the conveyor, or the printed sheet is damaged, it is unqualified.

[0057] Qualified index: The peeling defect rate of the same batch of printed sheets is less than 0.1%, which meets the requirements.

[0058] (3) Product performance test:

[0059] The performance tests were conducted on the products prepared in the above examples and comparative examples. The test methods or instruments, test conditions and qualification standards are shown in Table 3 below.

[0060] Table 3

[0061]

[0062]

[0063] The viscosity, solid content, and magnetic strength properties of Examples 1-9 and Comparative Examples 1-6 are shown in Table 4 below.

[0064] Table 4

[0065] Viscosity (cPs) Solid content (%) Magnetic strength performance Example 1 26208 54 OK Example 2 20150 56 OK Example 3 35100 51 OK Example 4 27253 54 OK Example 5 19580 56 OK Example 6 35820 51 OK Example 7 22580 54 OK Example 8 18508 56 OK Example 9 28458 51 OK Comparative Example 1 17786 56.5 NG Comparative Example 2 36752 50.5 OK Comparative Example 3 17962 56.5 NG Comparative Example 4 36882 50.5 OK Comparative Example 5 17028 56.5 NG Comparative Example 6 36085 50.5 OK

[0066] The magnetic strength performance, durability, corrosion resistance, and weld resistance of Examples 10-13 and Comparative Examples 7-15 are shown in Table 5 below.

[0067] Table 5

[0068]

[0069]

[0070] In terms of process, the printing thickness and the corresponding magnetic field strength are set within the intensity range to meet the required standards (Examples 10-13, Comparative Examples 7-15). After obtaining good peeling effect and precise lamination, the product performance shows higher durability, moisture resistance and solder resistance qualification rate: Example 1 and Examples 10-11 are set to different printing thicknesses and magnetic field strengths; Examples 4 and 12-13 are set to pure organic complex organic matter; Comparative Examples 7-8 are set to nickel paste printing thickness that is not within the prescribed range (performance is unqualified); Comparative Example 9 is set to a situation where there is no external magnetic field, that is, traditional vacuum adsorption is used for comparison with Example 1 (poor performance); Comparative Example 10 is set to a magnetic field strength greater than the prescribed value. Compared with Example 1, there is no obvious improvement in performance at this time; Comparative Example 11 is set to a conventional nickel paste without adding magnetic organic matter (performance is unqualified); Comparative Examples 12-15 are set to the case of metal complexes, and the performance also does not meet the standards.

[0071] Controlling the lamination quality of printed sheets through a more controllable and evenly distributed magnetic force is a more advanced and ideal method than vacuum adsorption. This method reduces the difference in deformation between the printed and blank areas, ensuring uniform force during peeling and stacking. This effectively solves problems such as deformation and damage to the printed sheets caused by uneven force during the peeling process, ultimately achieving a higher-quality peeling effect. The use of a controllable magnetic field enables precise positioning and tight bonding during lamination, greatly reducing defects caused by mechanical stacking offsets and significantly improving the yield rate of the MLCC production process.

[0072] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a multilayer ceramic capacitor, characterized in that: The following steps are involved: 1) preparing a ceramic sheet by coating the ceramic slurry on a carrier film; 2) printing a conductive paste on the surface of the ceramic sheet and drying it to obtain a printed sheet; 3) placing the printed sheet on a carrier, placing a transfer device on top of the printed sheet, and applying a magnetic field between the carrier and the transfer device to peel off the printed sheet to obtain a green part; 4) laminating the green parts, pressing the laminated green parts, cutting, debinding, sintering, and terminating. Producing the multilayer ceramic capacitor; In step 2), the conductive paste comprises the following components in percentage by weight: 38-63 wt% conductive metal powder, 5-12 wt% ceramic powder, 0.5-2 wt% dispersant, 0.5-2 wt% plasticizer, 30-50 wt% organic solvent, and 3-8 wt% magnetic organic matter; wherein the magnetic organic matter is at least one of nitroxide-substituted polydiacetylene, PANiCNQ, and CsNiCr(CN)6·2H2O; and the printed thickness of the conductive paste is 0.3-2 μm. In step 3), the magnetic field strength is 0.1-10T; In step 4), the lamination process is carried out in a controllable magnetic field, and during lamination, the laminated pieces and the pieces to be laminated are controlled to maintain opposite magnetic properties.

2. The method for preparing a multilayer ceramic capacitor according to claim 1, wherein: In step 1), the ceramic slurry comprises the following components in percentage by weight: 40-60 wt% of ceramic powder, 4-8 wt% of binder, 0.2-0.4 wt% of plasticizer, and 30-50 wt% of organic solvent.

3. The method for preparing a multilayer ceramic capacitor according to claim 1 or 2, wherein: In step 1), the thickness of the ceramic sheet is 1-20 μm.

4. The method for preparing a multilayer ceramic capacitor according to claim 1, wherein: In step 2), the conductive paste contains 5-8 wt% of magnetic organic matter.

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