MLCC and method for improving polarization cracking of MLCC

Abstract

The application relates to the field of electronic component manufacturing, in particular to a MLCC and a MLCC preparation method for improving polarization cracking of the MLCC. The preparation method provided by the application comprises a batching step and a laminating step; the batching step comprises, in sequence, a porcelain slurry pre-dispersion step, a first-step grinding step and a second-step grinding step; the porcelain slurry pre-dispersion step is carried out in a stirrer, and the first-step grinding step and the second-step grinding step are carried out in a sand mill. The laminating step comprises, in sequence, a drying step, a packaging step, a vacuumizing step, a laminating step, a cooling step and a bag opening step; in the drying step, the un-laminated bar block is subjected to drying treatment at 45-65 DEG C for 1-4 h; in the packaging step, the bar block is packaged by adopting a sandwich packaging method and is bagged, wherein the structure of the sandwich packaging method comprises, from top to bottom, a metal laminated cover plate, the bar block and a metal laminated plate. The product film prepared by the application scheme is free of patterns, lines and holes, has good compactness, and can effectively improve the polarization cracking problem in the capacitor.

Description

Technical Field

[0001] This application relates to the field of electronic component manufacturing, and in particular to an MLCC and a method for preparing an MLCC to improve polarization cracking. Background Technology

[0002] Capacitors are important electronic components, serving as containers for storing electrical charge and providing functions such as DC blocking, AC passing, resonance, filtering, bypassing, and coupling. MLCCs (Multi-layer Ceramic Capacitors), also known as chip multilayer ceramic capacitors, are made by stacking ceramic dielectric films with printed electrodes (internal electrodes) in a staggered manner, then sintering them at high temperatures in a single process to form a ceramic chip. Metal layers (external electrodes) are then sealed at both ends of the chip, creating a monolithic structure, hence the name monolithic capacitor. Based on temperature characteristics and materials, MLCCs can be classified into NPO, X7R, etc.

[0003] The existing traditional MLCC production process includes the following steps in sequence: material preparation, casting, screen printing, lamination, cutting, glue removal, sintering, chamfering, end sealing, end burning, electroplating, testing, appearance, and tape packaging. Among them, the existing lamination process includes bagging, vacuuming, lamination, cooling, and unpacking. In practice, the blocks are directly packaged and laminated without any other treatment before lamination, resulting in obvious polarization cracking in the final product.

[0004] Currently, both NPO and X7R products are manufactured using the aforementioned MLCC production process. However, using the traditional MLCC production process to manufacture NPO (NPO capacitors are a type of monolithic ceramic capacitor with temperature compensation characteristics) products can lead to polarization cracks inside the capacitor after sintering in some NPO products, resulting in problems such as poor capacitor reliability, low capacitance, and low withstand voltage. Summary of the Invention

[0005] To address the problems of the prior art mentioned in the background section, this application provides an improved method for fabricating MLCCs with polarization cracking, the technical solution of which is as follows:

[0006] The method for preparing MLCCs with improved polarization cracking provided in this application includes a batching step and a lamination step.

[0007] The batching steps include, in sequence, pre-dispersion of porcelain slurry, first-step grinding, and second-step grinding; wherein, the pre-dispersion of porcelain slurry is carried out in a mixer, and the first-step grinding and second-step grinding are carried out in a sand mill.

[0008] The lamination process includes baking, packaging, vacuuming, lamination, cooling, and unpacking. In the baking process, the unlamination blocks are baked at 45-65°C for 1-4 hours. In the packaging process, the blocks are packaged and bagged using a sandwich packaging method. The sandwich packaging method consists of a metal laminate cover, blocks, and a metal laminate from top to bottom.

[0009] In some embodiments, during the baking process, the unpressed dough blocks are baked at 55-60°C for 2 hours.

[0010] In some embodiments, the lamination step sequentially includes baking, packaging, vacuuming, lamination, cooling, and unpacking processes, the process of which is as follows:

[0011] Baking: Place the unpressed barley blocks at 45-65℃ for baking for 1-4 hours;

[0012] Packaging: The bar block is packaged and bagged using the sandwich packaging method. The sandwich packaging structure consists of a metal laminate cover plate, the bar block, and the metal laminate plate from top to bottom.

[0013] Vacuum sealing: After the bar blocks are bagged, the bag opening is heat-sealed and the air inside the bag is removed to seal the bar blocks;

[0014] Lamination: The packaged blocks are placed into a laminator for lamination.

[0015] Cooling: The laminated blocks are cooled;

[0016] Unpacking: Unpack the cooled block and collect the material.

[0017] In some embodiments, the process of the ingredient preparation step is as follows:

[0018] Pre-dispersion of porcelain slurry: Porcelain powder and solvent are mixed in a mixer to pre-dispersion, so that the porcelain powder and solvent are fully and evenly mixed to obtain porcelain slurry;

[0019] First step grinding: The porcelain slurry is placed in a sand mill for the first step grinding to obtain a first grinding slurry with a certain particle size range;

[0020] Second grinding step: The first grinding slurry is mixed evenly with the binder and plasticizer, and then ground in a sand mill to obtain a second grinding slurry with a certain particle size range;

[0021] Test output: Test the parameters of the second grinding slurry and output the slurry.

[0022] In some embodiments, the ceramic powder used in the ceramic slurry pre-dispersion process is MLC-320NB ceramic powder.

[0023] In some embodiments, the process of the ingredient preparation step is as follows:

[0024] Pre-dispersion of porcelain slurry: Porcelain powder and solvent are added to a mixer and stirred to pre-disperde the mixture, so that the porcelain powder and solvent are fully and evenly mixed to obtain porcelain slurry;

[0025] Step 1 Grinding: The porcelain slurry is first placed in tank A of the sand mill. The porcelain slurry is circulated and ground in tanks A and B of the sand mill to obtain a first grinding slurry with a certain particle size range.

[0026] The second step of grinding: The first grinding slurry is mixed evenly with the binder and plasticizer, and then ground in a sand mill. The mixed slurry is circulated and ground in tanks A and B of the sand mill to obtain a second grinding slurry with a certain particle size range.

[0027] Test discharge: Test the density, viscosity, and solid content parameters of the second grinding slurry. Discharge the slurry after passing the test.

[0028] The particle size of the first grinding slurry is (0.57~0.63) μm; the particle size of the second grinding slurry is (0.57~0.63) μm.

[0029] In some embodiments, the sand mill is a horizontal sand mill, and the grinding balls used in the first and second grinding processes are 0.5±0.03mm zirconium balls.

[0030] In some embodiments, both the metal laminate cover plate and the metal laminate are aluminum plates.

[0031] In some embodiments, the preparation method sequentially includes the steps of ingredient preparation, casting, screen printing, lamination, pressing, cutting, adhesive removal, sintering, chamfering, end sealing, end burning, electroplating, testing, appearance, and tape making.

[0032] This application provides an MLCC that is prepared using the MLCC fabrication method described above to improve MLCC polarization cracking.

[0033] Compared with existing technologies, this application has the following advantages:

[0034] The MLCC preparation method provided in this application for improving polarization cracking in MLCCs produces a film without patterns, lines, or holes, with good density, and can effectively improve the polarization cracking problem inside the capacitor. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 A schematic flowchart of the lamination step in the preparation method provided in this application;

[0037] Figure 2 A schematic diagram of the sandwich packaging method in the lamination step of the preparation method provided in this application;

[0038] Figure 3 This is a photograph of the surface of the cast film in Comparative Example 1.

[0039] Figure 4 This is a photograph of the surface of the cast film in Example 3;

[0040] Figure 5 Here is a physical image of the MLCC product in Comparative Example 2;

[0041] Figure 6 This is a physical image of the MLCC product in Example 3. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0043] This application provides the following operational example of an improved MLCC polarization cracking MLCC fabrication method:

[0044] Step 1: Select materials:

[0045] The ceramic powder used is MLC-320NB ceramic powder.

[0046] Step 2, Ingredients:

[0047] The specific process is as follows:

[0048] Pre-dispersion: The batching process is carried out in a pre-dispersion mixer. Porcelain powder and solvent are added to the mixer and stirred for 50-80 minutes to ensure thorough mixing. After mixing, the mixed slurry is pumped into tank A of a sand mill using a diaphragm pump. The sand mill is then turned on, and the porcelain slurry is circulated and ground in tanks A and B of the sand mill for the first grinding step (Step A). ​​After the first grinding reaches a suitable particle size, binder and plasticizer are added. After addition, the mixture is stirred for 30-60 minutes to ensure thorough mixing of the binder and porcelain slurry (ensuring the slurry viscosity is within a stable range). The sand mill is then turned on, and the mixed slurry is circulated and ground in tanks A and B of the sand mill for slurry mixing and the second grinding step (Step B). The particle size of the first ground slurry is (0.57-0.63) μm; the particle size of the second ground slurry is (0.57-0.63) μm.

[0049] The second step involves grinding until the particle size and other parameters are within a suitable range. Then, the slurry density, viscosity, and solid content are tested. Once qualified, the slurry is discharged. Step 3: Casting, screen printing, and lamination.

[0050] The slurry output after the batching step is then subjected to casting, screen printing, and layering processes, specifically:

[0051] Casting: Ceramic paste is evenly coated onto a release film of a certain thickness and baked at a certain temperature to form a dry ceramic blank film; Electrode Printing: Inner electrode paste is printed into an inner electrode pattern of a certain size and shape on the cast ceramic blank film (i.e., ceramic dielectric film) to obtain an electrode pattern dielectric film; Lamination: The printed electrode pattern dielectric films are stacked according to a certain misalignment to form the required MLCC Bar block (i.e., bar block). Step 4, Lamination:

[0052] like Figure 1 As shown, the lamination process flow is as follows:

[0053] Baking: Place the unpressed bread blocks in an oven and bake at 45-65℃ for 1-4 hours; Packaging: as follows Figure 2 As shown, the sandwich packaging method is used to package the bar blocks and bag them. The sandwich packaging structure, from top to bottom, consists of an upper aluminum plate, the bar block, and a lower aluminum plate. Vacuuming: After the bar blocks are bagged, the bag opening is heat-sealed and the air inside the bag is removed to seal the bar blocks. Lamination: The sealed bar blocks are placed in a laminator for lamination. Cooling: The laminated bar blocks are cooled. Unpacking: The cooled bar blocks are unpacked and collected, completing the lamination process. Step 5: Cutting, glue removal, sintering, chamfering, end sealing, end burning, electroplating, testing, appearance, and tape taping.

[0054] The laminated blocks are sequentially processed through cutting, glue removal, sintering, chamfering, end sealing, end firing, electroplating, testing, appearance inspection, and tape packaging to obtain MLCC products. Specifically:

[0055] Cutting: The laminated blank is cut into individual blanks according to a certain step distance to obtain ceramic green blanks; Debinding: The ceramic green blanks are heated according to a certain temperature curve to remove the adhesive and other organic substances inside the chip; Sintering: The ceramic chip is sintered at high temperature according to the temperature curve to give the chip a certain mechanical strength; Chamfering: According to the process requirements, the electrodes inside the sintered ceramic chip are fully exposed by a chamfering machine; End sealing: End paste is applied to the two ends of the exposed electrodes of the product to seal the two ends and form the external electrodes; End firing: The end-sealed product is placed in a high-temperature furnace to fire the ends, so that the end electrodes are in close contact with the electrode plate to form the ceramic capacitor prototype; Electroplating: A metal layer is plated on the electrodes of the ceramic capacitor prototype to form the ceramic capacitor assembly; Appearance: Ceramic capacitor assemblies with surface defects are removed; Testing: The electrical performance of the capacitor products (withstand voltage BV, capacitance Cp, loss DF, and insulation resistance IR, etc.) are tested, and defective products are rejected; Packaging: The capacitor products are packaged according to the size and quantity requirements. To verify the effectiveness of this application, the following embodiments and comparative examples are also provided:

[0056] Examples 1-3 (Preparation of NPO products)

[0057] Step 1: Select materials:

[0058] The ceramic powder used is MLC-320NB ceramic powder, the solvent used is diluent (toluene and anhydrous ethanol mixed at a weight ratio of 7:3), the binder used is LF02, the plasticizer used is DOP, and the dispersant used is AKM-0531.

[0059] The formula is as follows: 60,000g ceramic powder, 30,600g binder, 2,460g plasticizer, 22,380g solvent, and 780g dispersant.

[0060] Step 2, Ingredients:

[0061] The specific process is as follows:

[0062] Pre-dispersion: The batching process is carried out in a pre-dispersion mixer. The ceramic powder and solvent are added to the mixer and stirred for 60 minutes to ensure thorough mixing. After mixing, the slurry is pumped into tank A of a horizontal sand mill using a diaphragm pump. The horizontal sand mill is then started, and the slurry circulates multiple times between tanks A and B to complete the first grinding step (Step A). ​​The grinding balls used in the first grinding step are 0.5mm diameter zirconium balls with a ball-to-powder weight ratio of 1:0.082. The particle size of the first grinding slurry is 0.60±0.03μm. The grinding process is as follows: the main unit of the horizontal sand mill rotates at 30 Hz, the pump speed is 30 Hz, the stirring speed of tank A is 27 Hz, the stirring speed of tank B is 27 Hz, and tanks A and B circulate back and forth 20 times (that is, the slurry is ground from tank A by the main unit and discharged to tank B for one cycle, then ground from tank B by the main unit and circulated back to A, and so on, tank A to B is 1 cycle, B to A is 2 cycles, and so on, for a total of 20 cycles).

[0063] After grinding to a suitable particle size in the first step, binders and plasticizers are added to the slurry. After mixing for 30 minutes, the horizontal sand mill is started. The mixed slurry is circulated and ground in tanks A and B of the sand mill to complete the slurry mixing and the second grinding step (step B). The grinding balls used in the second grinding step are 0.5mm diameter zirconium balls with a ball-to-material weight ratio of 1:0.060. The particle size of the first ground slurry is 0.60±0.03μm. The grinding process is as follows: the main motor speed of the horizontal sand mill is 30Hz, the pump speed is 30Hz, the stirring speed in tank A is 27Hz, the stirring speed in tank B is 27Hz, and the slurry is circulated back and forth between tanks A and B 10 times (i.e., the slurry is ground in tank A, discharged to tank B, circulated once, then ground in tank B and circulated back to A, and so on, for a total of 10 times).

[0064] The second step involves grinding until the particle size and other parameters are within a suitable range. Then, the slurry density, viscosity, and solid content are tested. Once qualified, the slurry is discharged. Step 3: Casting, screen printing, and lamination.

[0065] The slurry output after the batching step is then subjected to casting, screen printing, and layering processes, specifically:

[0066] Casting: Ceramic paste is evenly coated onto a release film of a certain thickness and baked at a certain temperature to form a dry ceramic blank film; Electrode Printing: Inner electrode paste is printed into an inner electrode pattern of a certain size and shape on the cast ceramic blank film to obtain an electrode pattern dielectric film; Lamination: The printed electrode pattern dielectric films are stacked according to a certain misalignment to form the required MLCC Bar block (i.e., bar block). Step 4: Lamination:

[0067] The lamination process flow is as follows:

[0068] Baking: The unpressed dough blocks were placed in an oven and baked at a specific temperature. The specific baking temperatures for different experimental groups are detailed in Table 1 below. Table 1

[0069]

[0070] Packaging: The bar block is packaged and bagged using a sandwich packaging method. The sandwich packaging structure consists of an upper metal plate, the bar block, and a lower metal plate from top to bottom. The top layer is an aluminum plate with a Teflon-plated surface and is a square with a side length of 153mm. The middle layer is the pressed bar block product, which is a square with a side length of 155mm. The bottom layer is an aluminum plate with a zinc-plated surface and is a square with a side length of 180mm.

[0071] Vacuuming: After the bar block is bagged, the bag opening is heat-sealed and the air inside the bag is removed to seal the bar block; Lamination: The sealed bar block is placed in a laminator for lamination; The lamination operation is carried out according to a certain pressure curve, the specific pressure curve is shown in Table 2 below.

[0072] Table 2

[0073]

[0074] Cooling: The laminated blocks are cooled; Bag removal: The cooled blocks are unpacked and collected, completing the lamination process. Step 5: Cutting, glue removal, sintering, chamfering, end sealing, end burning, electroplating, testing, appearance inspection, and tape weaving.

[0075] The laminated blocks are sequentially processed through cutting, glue removal, sintering, chamfering, end sealing, end firing, electroplating, testing, appearance inspection, and tape packaging to obtain MLCC products. Specifically:

[0076] Cutting: The laminated green body is cut into individual green bodies according to a certain step distance; Debinding: The ceramic green body is heated at 250-300℃ to remove the adhesive and other organic substances inside the chip; Sintering: The debinded product is sintered at a high temperature of 1270-1300℃ for 35-40 hours; Chamfering: According to the process requirements, the electrodes inside the sintered ceramic chip are fully exposed using a chamfering machine; End sealing: End paste is applied to the two ends of the exposed electrodes of the product to seal the two ends and form the external electrodes; End firing: The sealed product is then fired... The product is placed in a high-temperature furnace for sintering, ensuring close contact between the end electrodes and the electrode plate to form the initial ceramic capacitor body; electroplating: a metal layer is plated onto the electrodes of the initial ceramic capacitor body to form the final ceramic capacitor body; appearance: ceramic capacitor bodies with surface defects are removed; testing: the electrical performance of the capacitor products (withstand voltage BV, capacitance Cp, loss DF, and insulation resistance IR, etc.) are tested, and defective products are rejected; packaging: the capacitor products are packaged according to size and quantity requirements to complete the MLCC product manufacturing. Comparative Example 1 (traditional material preparation process, the material preparation steps are different from the example).

[0077] The only difference from Example 3 is the ingredient preparation steps. The comparative example's ingredient preparation process is as follows:

[0078] The mixing and grinding operations from feeding to discharging are all carried out in the same ball mill. That is, the porcelain slurry pre-dispersion process, the first grinding step (step A) and the second grinding step (step B) in Example 3 are all carried out in the same ball mill.

[0079] The first grinding step uses two types of zirconium balls with diameters of 3mm and 5mm (weight ratio 1:1), with a ball-to-material weight ratio of 1:5.68. The grinding process parameters are: ball mill speed of 45 rpm and grinding time of 5 hours. The second grinding step uses two types of zirconium balls with diameters of 3mm and 5mm (weight ratio 1:1), with a ball-to-material weight ratio of 1:4.6. The grinding process parameters are: ball mill speed of 45 rpm and grinding time of 13 hours.

[0080] The other preparation processes and conditions are the same as in Example 3.

[0081] Comparative Example 2 (Traditional lamination process, the lamination steps are different from those in the example).

[0082] The only difference from Example 3 is the lamination process. The lamination process in this comparative example is as follows: packaging, vacuuming, lamination, cooling, and unpacking; the packaging blocks undergo no further processing before lamination, but are directly packaged and then laminated. The specific process is as follows:

[0083] Packaging: The traditional sandwich packaging method is used, with PET film covering the top and bottom surfaces of the bar and then bagged.

[0084] Vacuuming: Same as in Example 3;

[0085] Lamination: The packaged block is placed in a laminator and laminated according to a certain pressure curve. The lamination process is the same as in Example 3.

[0086] Cooling: The laminated blocks are cooled, in the same process as in Example 3;

[0087] Unpacking: Unpack the cooled bar blocks and collect the material, the process is the same as in Example 3;

[0088] The other preparation processes and conditions are the same as in Example 3.

[0089] Comparative Example 3 (raw materials differ from those in the Example 1)

[0090] The only difference from Example 3 is that FW-K30N ceramic powder was used. All other preparation processes and conditions were the same as in Example 3.

[0091] The performance of the cast films and MLCC products in the examples and comparative examples was tested accordingly:

[0092] The test results are shown in Table 3 below:

[0093] Table 3

[0094]

[0095] Analysis of the test data shows that:

[0096] 1. The density of the cast film surface:

[0097] like Figure 3 As shown, the surface of the cast film in Comparative Example 1 has patterns, lines, and holes, and its density is poor; Figure 4 As shown, the cast film of Example 3 has no patterns, lines, or pores on its surface, exhibiting good density. The reason for this is:

[0098] Comparative Example 1 uses the existing batching process, and the mixing and grinding (step A + step B) operations from feeding to discharging are all carried out in the same ball mill. This operation method has the following problems: poor slurry dispersion and uneven particle size distribution: As an old-fashioned machine, the ball mill uses large-sized zirconium balls (3-5mm), which will result in poor slurry grinding and dispersion, uneven particle distribution, etc., which leads to poor dispersion of the cast film, and the film has patterns, lines, holes and poor density.

[0099] The embodiment optimizes the batching process by selecting appropriate specific ceramic powder and combining it with the optimized batching process, so that the ceramic slurry has uniform particle size and good dispersibility, resulting in a cast film surface without patterns, lines, or holes, and with good density.

[0100] 2. Polarization cracking of MLCC products

[0101] From data and Figure 5-6 It can be seen that: compared to Example 3, as Figure 5 Comparative Example 2, which uses a conventional lamination process, exhibits significant polarization cracking. Furthermore, compared to Example 3, Comparative Example 3 also shows significant polarization cracking. Figure 6 As shown, there is no polarization cracking phenomenon in Example 3.

[0102] The MLCC fabrication method for improving polarization cracking, as optimized in this application, significantly improves polarization cracking through the selection of ceramic powder materials and the optimized and adjusted batching and lamination steps. The reason for this is as follows:

[0103] Firstly, the existing lamination process involves bagging, vacuuming, lamination, cooling, and unpacking. The packaging blocks undergo no pretreatment before lamination; they are directly packaged and then laminated. This direct lamination without further processing causes significant stress on the blocks due to the temperature and pressure within the laminator. This stress, combined with subsequent adhesive removal and sintering processes, leads to significant polarization cracking observed after destructive physical analysis (DPA).

[0104] The improved lamination process of this application consists of baking the bar, bagging (sandwich packaging method using metal plates), vacuuming, lamination, cooling, and unpacking. The original direct lamination is replaced with pre-lamination baking of the bar blocks in an oven, with optimized baking conditions to create specific process parameters. The baking of the unlamination bar blocks in the oven heats the interior, generating slight stress and initially softening the blocks. This solves the problem of polarization cracking caused by rapid extrusion during lamination, improving the reliability of the capacitor products. Furthermore, traditional sandwich packaging uses PET film to cover the bar block surface. PET film is relatively soft, and lamination causes significant stretching and deformation of the bar blocks. This application replaces the PET film with a metal plate in the lamination step, resulting in less stretching and deformation of the bar blocks after lamination, and the metal plate can be reused.

[0105] Secondly, as the main material of capacitors, different ceramic powders affect polarization cracking. Therefore, to improve polarization cracking, it is necessary to select a suitable ceramic powder and match it with the corresponding preparation process. Existing NPO products use FW-K30N ceramic powder, but after verification, it was found that the improvement of polarization cracking was not good when using FW-K30N ceramic powder. This application uses a specific MLC-320NB ceramic powder and an optimized preparation process. This ceramic powder has good dispersion and uniform particle distribution, and the electrical performance and reliability of the resulting product meet the technical requirements.

[0106] In addition, this application further optimizes the baking process parameters. As can be seen from the data in Table 2, baking at 55℃ for 2 hours is the best choice, which has the best effect on improving polarization cracks in MLCCs.

[0107] In summary, compared with the prior art, the MLCC fabrication method for improving polarization cracking provided in this application has the following design concept and effects:

[0108] The polarization cracking phenomenon in NPO material capacitors under existing manufacturing processes can be effectively solved by the MLCC fabrication method for improving polarization cracking provided in this application.

[0109] The MLCC manufacturing process includes, in sequence: raw material preparation, casting, screen printing, lamination, cutting, adhesive removal, sintering, chamfering, end sealing, end firing, electroplating, testing, appearance, and tape packaging. This application primarily improves polarization cracking by specifically selecting raw materials, optimizing the raw material preparation process, and optimizing the lamination process. It mainly consists of three parts: selecting ceramic powder, adjusting the raw material preparation process, and adjusting the lamination process, as detailed below:

[0110] 1. Select porcelain powder

[0111] Ceramic powder is the main material of capacitors, and different types of ceramic powder have an impact on polarization cracking. Therefore, in order to improve polarization cracking, it is necessary to select appropriate ceramic powder and match it with the corresponding preparation process.

[0112] Existing NPO products use FW-K30N ceramic powder, but after verification, it was found that the improvement of polarization cracking was not satisfactory when using FW-K30N ceramic powder. This application uses a specific MLC-320NB ceramic powder combined with an optimized preparation process. This ceramic powder has good dispersion and uniform particle distribution, and the electrical properties and reliability of the resulting product meet the technical requirements.

[0113] 2. Adjust the ingredient preparation process

[0114] The existing batching process involves mixing and grinding (step A + step B) from feeding to discharging all within the same ball mill. This method has the following problems: poor slurry dispersion and uneven particle size distribution. As an older type of machine, the ball mill uses relatively large zirconium balls (3-5mm), which can lead to poor slurry grinding and dispersion, uneven particle distribution, and thus poor dispersion of the cast film, resulting in patterns, lines, holes, and poor density on the film.

[0115] This application optimizes the batching process by performing pre-dispersion independently in a mixer and adjusting the grinding in the ball mill to a two-step process in a horizontal sand mill, with corresponding adjustments to the ball mill size. The grinding process involves circulating grinding in tanks A and B, resulting in good slurry dispersibility and particle size uniformity. By selecting suitable specific ceramic powder and combining it with the optimized batching process, the ceramic slurry achieves uniform particle size and dispersibility, resulting in a cast film surface free of patterns, lines, and pores, exhibiting excellent density.

[0116] 3. Adjusting the lamination process:

[0117] The existing lamination process involves bagging, vacuuming, lamination, cooling, and unpacking. The packaging blocks undergo no pretreatment before lamination; they are directly packaged and then laminated. This direct lamination without prior treatment causes significant stress on the blocks due to the temperature and pressure within the laminator. This stress, combined with subsequent adhesive removal and sintering processes, leads to polarization cracking observed during destructive physical analysis (DPA).

[0118] The improved lamination process of this application is as follows: baking, bagging (sandwich packaging method with metal plates pressed together), vacuuming, lamination, cooling, and unpacking.

[0119] The original direct lamination was replaced with pre-lamination oven drying of the unlaminated blocks, with optimized drying conditions to create specific process parameters. The oven drying process heats the unlaminated blocks, generating slight stress and initially softening them. This solves the problem of polarization cracking caused by rapid extrusion during lamination, thus improving the reliability of capacitor products.

[0120] Furthermore, the packaging process has also been adjusted: the traditional sandwich packaging process uses PET film to cover the surface of the sandwich block. PET film is relatively soft, and after lamination, the sandwich block will be stretched and deformed significantly. In this application, the lamination step is changed from PET film to metal plate, which makes the sandwich block less stretched and deformed after lamination, and the metal plate can be reused.

[0121] In addition, this application further optimizes the baking process parameters, and the optimal choice is to bake at 55°C for 2 hours. Under this process condition, the improvement of polarization cracking in MLCCs is the best.

[0122] In summary, this application, through the specific selection of raw materials, optimization and adjustment of the batching steps, and optimization and adjustment of the lamination steps, produces a product film without patterns, lines, or holes, with good density, and can effectively improve the polarization cracking problem of the product.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing MLCCs with improved polarization cracking, characterized in that: This includes the ingredient preparation step and the lamination step; The process of the ingredient preparation step is as follows: Pre-dispersion of porcelain slurry: Porcelain powder and solvent are added to a mixer and stirred to pre-disperde the mixture, so that the porcelain powder and solvent are fully and evenly mixed to obtain porcelain slurry; Step 1 Grinding: The porcelain slurry is first placed in tank A of the sand mill. The porcelain slurry is circulated and ground in tanks A and B of the sand mill to obtain a first grinding slurry with a certain particle size range. The second step of grinding: The first grinding slurry is mixed evenly with the binder and plasticizer, and then ground in a sand mill. The mixed slurry is circulated and ground in tanks A and B of the sand mill to obtain a second grinding slurry with a certain particle size range. Test discharge: Test the density, viscosity, and solid content parameters of the second grinding slurry. Discharge the slurry after passing the test. The particle size of the first grinding slurry is 0.57–0.63 μm; the particle size of the second grinding slurry is 0.57–0.63 μm; and the ceramic powder used is MLC-320NB ceramic powder. The lamination process includes baking, packaging, vacuuming, lamination, cooling, and unpacking in sequence. Baking: Place the unpressed barley blocks at 55-60℃ for baking for 2 hours; Packaging: The bar block is packaged and bagged using the sandwich packaging method. The sandwich packaging structure consists of a metal laminate cover plate, the bar block, and the metal laminate plate from top to bottom. Vacuum sealing: After the bar blocks are bagged, the bag opening is heat-sealed and the air inside the bag is removed to seal the bar blocks; Lamination: The packaged blocks are placed into a laminator for lamination. Cooling: The laminated blocks are cooled; Unpacking: Unpack the cooled block and collect the material.

2. The method for preparing MLCCs with improved polarization cracking according to claim 1, characterized in that, The sand mill is a horizontal sand mill, and the grinding balls used in the first and second grinding processes are 0.5±0.03mm zirconium balls.

3. The method for preparing MLCCs with improved polarization cracking according to claim 1, characterized in that, Both the metal laminate cover plate and the metal laminate are aluminum plates.

4. The method for preparing MLCCs with improved polarization cracking according to claim 1, characterized in that, The process includes, in sequence, ingredient preparation, casting, screen printing, lamination, pressing, cutting, glue removal, sintering, chamfering, end sealing, end burning, electroplating, testing, appearance, and tape making.

5. An MLCC, characterized in that: The MLCC was prepared using the method for improving polarization cracking of MLCC as described in any one of claims 1-4.

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