MLCC product and manufacturing method thereof

Abstract

The invention relates to the technical field of ceramic capacitors, in particular to an MLCC product and a manufacturing method thereof. The manufacturing method of the MLCC product comprises the following steps: S1, preparing a plurality of test samples; s2, measuring the total capacitance of each test sample; s3, calculating the capacitance of the capacitor unit corresponding to each K value based on the total capacitance and the number of the capacitor units in each test sample; s4, determining structural parameters of the MLCC product according to the target capacitance and the target thickness of the MLCC product and the capacitance of each capacitor unit; and S5, performing lamination assembly according to the structural parameters to form an MLCC product. The manufacturing method not only improves the capacity hit qualified rate of MLCC products, but also simplifies the production process, saves a large amount of manpower and materials, greatly reduces the manufacturing cost, has the advantages of high qualified rate and good economical efficiency, and is very suitable for large-scale production of MLCC products with different sizes and different capacitances.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of MLCC manufacturing, and particularly relates to an MLCC product and a manufacturing method thereof. BACKGROUND

[0002] Multi-layer Ceramic Capacitors (MLCC) are a kind of capacitors with ceramic as dielectric material and multi-layer stacked structure. MLCC has the advantages of small size, large capacity, high temperature resistance, and good high frequency characteristics, and can be applied to various circuits such as oscillation circuit, timing or delay circuit, coupling circuit, decoupling circuit, etc., and is widely used in consumer electronics, vehicle electronics, base stations, servers and security industries.

[0003] According to the temperature characteristics of ceramic dielectric materials, MLCC products can be divided into two categories: the first category includes temperature compensation type ceramic capacitors such as C0G (NP0), which is referred to as 1st ceramic; the second category includes high dielectric constant type ceramic capacitors such as X7 series, X6 series, X5 series, which is referred to as 2nd ceramic. Among them, the design capacity of products such as C0G in the 1st ceramic is small, and the control range of capacity tolerance is small. In addition, slight fluctuations in factors such as film thickness, length and width of printed electrodes, and layering accuracy will be significantly amplified, resulting in low capacity hit rate of MLCC products. SUMMARY

[0004] Therefore, it is necessary to provide an MLCC product and a manufacturing method thereof to solve the problem of low capacity hit rate of MLCC products.

[0005] The above-mentioned purpose of the present application is achieved by the following technical solutions: In a first aspect, the present application provides a manufacturing method of an MLCC product, comprising the following steps: S1: preparing a plurality of test samples, each test sample comprising a plurality of first electrode layers and a plurality of second electrode layers arranged alternately along the stacking direction, the first electrode layers and the second electrode layers each comprising a ceramic dielectric film and an inner electrode printed thereon, and the inner electrodes of the two are cross arranged to form a capacitor unit; a continuous K blank dielectric layer is arranged between adjacent first electrode layers and second electrode layers; wherein K is a natural number, and for each test sample, the K values of all capacitor units inside are the same; among the plurality of prepared test samples, there are test samples with different K values; S2: measuring the total capacitance of each test sample; S3: based on the total capacitance measured in step S2 and the number of capacitor units inside each test sample, calculating the capacitance of the capacitor units corresponding to each K value; S4: determining the structure parameters of the MLCC product according to the target capacitance, the target thickness and the capacitances of the capacitive units calculated in step S3, wherein the structure parameters include the number of the capacitive units corresponding to each K value and the arrangement order of the capacitive units in the stacking direction; S5: performing the stacking assembly according to the structure parameters determined in step S4 to form the MLCC product.

[0006] In one of the embodiments, the MLCC product includes a first protective cover, a capacitive core and a second protective cover arranged in sequence in the stacking direction, the capacitive core is composed of a plurality of the capacitive units arranged in the stacking direction, the first protective cover is composed of M blank dielectric layers arranged in the stacking direction, and the second protective cover is composed of N blank dielectric layers arranged in the stacking direction. In step S4, the structure parameters further include the values of M and N, wherein M and N are each independently selected from any integer not less than 5, and the absolute value of the difference between M and N is less than or equal to 2.

[0007] In one of the embodiments, in step S4, the arrangement order of the capacitive units in the stacking direction satisfies: taking the central axis of the stacking direction as the reference, the absolute value of the difference between the K values of the capacitive units equidistant from the central axis is not more than 5.

[0008] In one of the embodiments, among the plurality of test samples prepared, there is a test sample including at least three capacitive units with different K values.

[0009] In one of the embodiments, the number of the capacitive units in the same test sample is not less than 3.

[0010] In one of the embodiments, the K value is selected from any natural number between 0 and 8.

[0011] In one of the embodiments, after step S3, the following step is further included: based on the K value and the capacitances of the capacitive units calculated in step S3, a function relationship between the K value and the capacitance of the capacitive unit is fitted to calculate the capacitance of the capacitive unit corresponding to other K values.

[0012] In one of the embodiments, the function relationship is a monomial polynomial function, and the determination coefficient R 2 ≥ 0.98.

[0013] In one of the embodiments, the ceramic dielectric film and the blank dielectric layer are both prepared by the tape casting method, and the thickness of each ceramic dielectric film and each blank dielectric layer is consistent.

[0014] In a second aspect of the present application, an MLCC product is provided, which is manufactured using the manufacturing method of the MLCC product as described above.

[0015] This application has at least the following beneficial effects: This application, based on the design concept that the capacitance of a capacitor cell and the dielectric thickness do not completely follow an inverse proportional relationship during the production process, adopts the following method to determine the capacitance of each capacitor cell: the K value of all capacitor cells within each test sample is kept consistent, and multiple test samples with different K values ​​are prepared; the total capacitance of each test sample is tested, and the capacitance of the capacitor cell corresponding to each K value is calculated based on the number of capacitor cells within each test sample. Based on the target capacitance and target thickness of the MLCC product and the capacitance of the capacitor cell corresponding to each K value, the structural parameters of the MLCC product can be determined, and the MLCC product can be laminated and assembled.

[0016] As a result, not only can the capacity design accuracy of MLCC products be greatly improved and the capacity hit rate be guaranteed, but there is also no need to repeatedly adjust the test samples, which effectively simplifies the production process, saves a lot of manpower and materials, and greatly reduces manufacturing costs. It has the advantages of high pass rate and good economy, and is very suitable for large-scale production of MLCC products of different sizes and different capacitances. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application and to more fully understand the present application and its beneficial effects, the following is a brief introduction to the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0018] Figure 1 1 is a schematic flow chart of a method for manufacturing an MLCC product in one embodiment; Figure 2 is a schematic structural diagram of a test sample numbered 100 in one embodiment; Figure 3 is a schematic structural diagram of a test sample numbered 200 in one embodiment; Figure 4 is a schematic structural diagram of a test sample numbered 300 in one embodiment; Figure 5 The K value and the capacitance C of the capacitor unit fitted in the embodiment are K Function relationship curve graph.

[0019] Reference numerals: 11, internal electrode; 12, ceramic dielectric sheet; 21, first electrode layer; 22, second electrode layer; 23, blank dielectric layer; 30, capacitor unit; 40, capacitor core; 51, first protective cover; 52, second protective cover; Z, stacking direction; 100, 200, 300, number of test samples. DETAILED DESCRIPTION

[0020] For the purposes of this application, particular embodiments are described in further detail below. The application, however, is realized in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the application to those skilled in the art.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0022] In this application, the meaning of "and / or" is inclusive, that is, "and / or" means either or both. The meaning of "at least" is inclusive, that is, "at least" means one or more. The meaning of "or" is exclusive, that is, "or" means either but not both. In this application, the meaning of "a," "an," and "the" is inclusive, that is, "a," "an," and "the" means one or more. In this application, the meaning of "in" includes "in" of and "in" on.

[0023] When a range of values is disclosed, unless otherwise base, the range is a continuous range including each and every value and sub-range within the range. Further, when the terms in and including are used, they are used al the open-ended terms "comprising" and "including" respectively. All ranges disclosed herein are also intended to include the endpoints and all the other sub-ranges between the endpoints of the ranges specified. In disclosing ranges, the endpoints are included and the ranges are inclusive of the integer values within the range. Unless otherwise stated, the disclosure of ranges includes the range itself; when a range of values is provided, it is intended to include the minimum and maximum values, and every value between the minimum and maximum values. Further, when a range of values is provided, it is intended to include the minimum and maximum values, and every value between the minimum and maximum values. Additionally, it is intended that when a parameter is provided as an optimal amount, range, or ratio, that optimum amount, range, or ratio can be expanded to other amounts, ranges, or ratios and are intended to be within the scope of the disclosure.

[0024] If not otherwise specified, all steps of the application can be performed in sequence or randomly. For example, the method comprises steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method can further comprise step (c) means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0025] In the present application, "above" or "below" includes the number itself. For example, 1 below includes 1.

[0026] In the present application, the temperature parameter, if not specifically limited, allows for both constant temperature treatment and variation within a certain temperature range. It should be understood that the constant temperature treatment allows for fluctuations within the accuracy range controlled by the instrument. Fluctuations within a range of, for example, ±5°C, ±4°C, ±3°C, ±2°C, ±1°C are allowed.

[0027] In the present application, room temperature refers to indoor temperature, normal temperature or general temperature. Generally, the range of room temperature can be any of the following temperature ranges: 23°C ± 2°C, 25°C ± 5°C or 20°C ± 5°C.

[0028] Please refer to Table 1. The design capacity of products such as C0G in Class 1 ceramic of MLCC products is small, and the control range of capacity tolerance is small. In MLCC products, two adjacent internal electrodes and the ceramic dielectric layer therebetween together form a capacitor unit, and the capacitance of each capacitor unit can be calculated using the following formula: C = (ε × 8.854 × S) ÷ D. Wherein, C is the capacitance of the capacitor unit, in picofarad (pF); ε is the relative dielectric constant (also known as the dielectric constant) of the ceramic dielectric material; S is the cross-sectional area of the two adjacent printed electrodes, in square millimeters (mm 2 ); D is the dielectric thickness of the capacitor unit (usually determined by the number of layers of ceramic dielectric layer between the two adjacent internal electrodes during production), in microns (μm). In the principle described in the above formula, the more layers of ceramic dielectric between the two adjacent internal electrodes, the smaller the capacitance of the corresponding capacitor unit. In an MLCC product, there are often combinations of capacitor units with different dielectric thicknesses.

[0029] Table 1. Target capacitance and control range of capacity tolerance of C0G / X7R In the traditional MLCC product design stage, after the capacitance of the capacitor unit provided with a single layer of ceramic dielectric layer is directly calculated according to the above formula, the number of capacitor units with different dielectric thicknesses and the stacking order of each capacitor unit constituting the MLCC product are usually determined according to the requirements of the target capacitance and the target thickness of the MLCC product. In the manufacturing stage, the statistical center point around which the capacitance distribution of the product is allowed in batch production is usually referred to as the capacitance center value. Due to the influence of the production process, the capacitance center value is not necessarily equal to the target capacitance. For example, the target capacitance of the MLCC product is 10 pF, and the qualified range is 9.95 pF~10.05 pF under the requirement of capacitance tolerance level A. If the capacitance center value is 10.1 pF, it means that the hit rate of the capacitance of the batch of MLCC products is very low, that is, the proportion of the actual capacitance of the product falling within the qualified range is very low.

[0030] The applicant found through research that the reason for the low hit rate of the capacitance in the traditional technology is that, in the manufacturing process, due to the influence of the particle size of the slurry, the thickness of the film, the surface roughness, the length and width of the printed electrode, the stacking accuracy, the sintering temperature and the sintering atmosphere and other production conditions, the actual capacitance and the dielectric thickness of the capacitor unit cannot completely follow the inverse proportional relationship of the formula, resulting in a difference between the theoretical capacitance and the actual capacitance of each capacitor unit with different dielectric thicknesses. Since the capacitance of the MLCC product is the sum of the capacitances of each capacitor unit, the slight difference in the capacitance of each capacitor unit will gradually be amplified, resulting in a too high deviation between the actual capacitance and the target capacitance of the MLCC product, and ultimately leading to a very low hit rate of the capacitance.

[0031] In the traditional technology, in order to ensure the hit rate of the capacitance, a small number of test samples are usually prepared for each model of the MLCC product according to the target capacitance, and further design adjustment is made according to the deviation between the actual capacitance and the target capacitance of the test sample, so as to determine the structure parameters of the MLCC product of this model.

[0032] For example, the MLCC product with metric size 0402 may require the production of dozens of models at a time, each model corresponding to a target capacitance. Each time a slurry film is manufactured, test samples need to be prepared and adjusted repeatedly according to the above method for each model, making the production process complicated, the test samples cannot be sold as finished products, a large amount of materials and labor are wasted, and the production cost is greatly increased.

[0033] Based on this, the first aspect of the present application provides a manufacturing method of an MLCC product, aiming to improve the capacity hit qualified rate of the MLCC product, and having the advantages of simplifying the process steps, saving materials and manpower, and reducing production costs.

[0034] In some embodiments, as shown in Figure 1 The manufacturing method of the MLCC product comprises the following steps: S1: preparing a plurality of test samples, each test sample comprising a plurality of first electrode layers and a plurality of second electrode layers arranged alternately along the stacking direction, the first electrode layer and the second electrode layer each comprising a ceramic dielectric film and an internal electrode printed thereon, and the internal electrodes of the two being arranged in cross to form a capacitor unit; a continuous K blank dielectric layer is arranged between adjacent first electrode layers and second electrode layers, wherein K is a natural number, and for each test sample, the K value of all capacitor units inside is the same; among the plurality of prepared test samples, there are test samples with a plurality of different K values; S2: measuring the total capacitance of each test sample; S3: based on the total capacitance measured in step S2 and the number of capacitor units inside each test sample, calculating the capacitance of the capacitor unit corresponding to each K value; S4: determining the structure parameters of the MLCC product according to the target capacitance and target thickness of the MLCC product and the capacitance of each capacitor unit calculated in step S3, the structure parameters including the number of capacitor units corresponding to each K value and the arrangement order of each capacitor unit in the stacking direction; S5: stacking and assembling according to the structure parameters determined in step S4 to form the MLCC product.

[0035] Based on the design idea that the capacitance of the capacitor unit and the dielectric thickness do not completely follow the inverse proportional relationship in the production process, the present application adopts the following method to determine the capacitance of each capacitor unit: keeping the K value of all capacitor units inside each test sample consistent, and preparing a plurality of test samples with a plurality of different K values; testing the total capacitance of each test sample, and calculating the capacitance of the capacitor unit corresponding to each K value according to the number of capacitor units inside each test sample. According to the target capacitance and target thickness of the MLCC product and the capacitance of the capacitor unit corresponding to each K value, the structure parameters of the MLCC product can be determined, and the MLCC product can be obtained by stacking and assembling.

[0036] Therefore, not only can the capacity design precision of the MLCC product be greatly improved to ensure the capacity hit qualified rate, but also the production process is effectively simplified, a large amount of manpower and materials are saved, and the manufacturing cost is greatly reduced, which has the advantages of high qualified rate and good economy, and is very suitable for the mass production of MLCC products of different sizes and different capacitances.

[0037] The following description is made in connection with Figures 1-4 The manufacturing method of the MLCC product is described step by step.

[0038] S1: preparing a plurality of test samples. Each test sample includes a plurality of first electrode layers 21 and a plurality of second electrode layers 22 arranged alternately along the stacking direction Z, the first electrode layers 21 and the second electrode layers 22 each include a ceramic dielectric film 12 and an inner electrode 11 printed thereon, and the inner electrodes 11 of the two are arranged in cross to form a capacitor unit 30; a continuous K blank dielectric layer 23 is arranged between adjacent first electrode layers 21 and second electrode layers 22.

[0039] In some embodiments, the ceramic dielectric film 12 and the blank dielectric layer 23 are both made of the same ceramic dielectric material, so that the thickness and the relative dielectric constant ε of each capacitor unit 30 remain consistent.

[0040] In some embodiments, the ceramic dielectric film 12 and the blank dielectric layer 23 are both prepared by tape casting method, and the thickness of each ceramic dielectric film 12 and each blank dielectric layer 23 remains consistent, so as to accurately control the dielectric thickness D of each capacitor unit 30. For example, the thickness of the ceramic dielectric film 12 and each blank dielectric layer 23 is 3 μm to 20 μm, such as 3 μm, 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, 17 μm, 20 μm, etc.

[0041] It can be understood that the ceramic dielectric material used by the ceramic dielectric film 12 and the blank dielectric layer 23 is the same, and the thickness of the two is also the same, that is, the blank dielectric layer 23 and the ceramic dielectric film 12 are actually the same film.

[0042] However, the present application is not limited thereto, and in other specific examples, the ceramic dielectric material and / or thickness used by the ceramic dielectric film 12 and the blank dielectric layer 23 can also be different, and those skilled in the art can make adaptive adjustment according to actual production conditions and product performance requirements.

[0043] The first electrode layer 21 and the second electrode layer 22 each include a ceramic dielectric film 12 and an inner electrode 11 printed thereon, the conductive materials used by the inner electrodes 11 of the two are the same, and the printing length, the printing width and the printing thickness are also the same, the only difference is that the inner electrodes 11 of the two are arranged in cross in the stacking direction Z. Among them, the cross arrangement means that the vertical projection area of the inner electrodes 11 of the two in the stacking direction Z at least partially overlaps.

[0044] During the membrane production process, the internal electrodes 11 of the first electrode layer 21 and the second electrode layer 22 can be printed on either surface of the ceramic dielectric diaphragm 12. During the lamination assembly process, the first and second electrode layers 21, 22 are arranged with the surfaces on which the internal electrodes 11 are printed facing upward (or downward) to prevent the internal electrodes 11 of the first and second electrode layers 21, 22 from contacting each other and causing a short circuit.

[0045] K continuous blank dielectric layers 23 are provided between the first electrode layer 21 and the second electrode layer 22. K is a natural number, i.e., K can be selected from any integer not less than zero, including but not limited to 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 100, etc. Furthermore, the value of K can be selected from any natural number between 0 and 8. Furthermore, the value of K can be selected from any natural number between 0 and 4.

[0046] Given that the larger the K value, the larger the dielectric thickness D of the capacitor unit 30, the lower the capacitance of the capacitor unit 30. If the K value is selected as a smaller natural number, a capacitor unit 30 with higher capacitance can be obtained, which is conducive to the preparation of high-capacitance, small-volume MLCC products.

[0047] The capacitor unit 30 is composed of a first electrode layer 21, K consecutive blank dielectric layers 23 and a second electrode layer 22 which are stacked in sequence, and the K value of all capacitor units 30 in each test sample is the same.

[0048] Let the number of first electrode layers 21 be α, the number of second electrode layers 22 be β, and the number of capacitor cells 30 be θ. Then, θ = α + β - 1. Let the thickness of the blank dielectric layer 23 and the ceramic dielectric diaphragm 12 be d. Then, the dielectric thickness of the capacitor cell 30, D = (K + 1) × d. If the thicknesses of the blank dielectric layer 23 and the ceramic dielectric diaphragm 12 are different, and are denoted by d1 and d2, respectively, then the dielectric thickness of the capacitor cell 30, D, = K × d1 + d2.

[0049] like Figure 2 As shown, in the test sample numbered 100, there are 5 capacitor units 30 inside, and the K value of all capacitor units 30 is 1, that is, a blank dielectric layer 23 is provided between the first electrode layer 21 and the second electrode layer 22, and each capacitor unit 30 is composed of a first electrode layer 21, a blank dielectric layer 23 and a second electrode layer 22 stacked in sequence.

[0050] like Figure 3As shown, in the test sample numbered 200, which has 3 capacitor units 30 inside, the K value of all capacitor units 30 is 0, i.e. no blank dielectric layer 23 is arranged between the first electrode layer 21 and the second electrode layer 22, and each capacitor unit 30 is composed of one first electrode layer 21 and one second electrode layer 22.

[0051] As shown, in the test sample numbered 300, which has 1 capacitor unit 30 inside, the K value of the capacitor unit 30 is 3, i.e. 3 blank dielectric layers 23 are arranged between the first electrode layer 21 and the second electrode layer 22, and the capacitor unit 30 is composed of the first electrode layer 21, the continuous 3 blank dielectric layers 23 and the second electrode layer 22 arranged in sequence. Figure 4

[0052] However, the present application is not limited to the above three examples. In some other examples, the K value of all capacitor units inside each test sample is the same and can be selected from any other natural number, and those skilled in the art can make appropriate adjustments according to the target capacitance and target thickness of the MLCC product and other preset conditions.

[0053] In some embodiments, the number of capacitor units 30 in the same test sample can be selected from any positive integer, for example, can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 50 or 100, etc. Further, the number of capacitor units 30 in the same test sample is not less than 3, so as to ensure the accuracy of the calculated capacitance of a single capacitor unit 30. Further, the number of capacitor units 30 in the same test sample is 3-8, so as to reduce the preparation cost while ensuring the calculation accuracy.

[0054] In some embodiments, among the plurality of test samples prepared, there are test samples with different K values. Further, among the plurality of test samples prepared, there are test samples with at least 3 different K values, and further preferably 3-8 different K values. The more the number of test samples with different K values, the more the number of capacitor units 30 with different thicknesses, and the more the number of capacitor units 30 that can be selected when determining the structure parameters of the MLCC product, which is conducive to further improving the capacity hit rate of the MLCC product and reducing the cost.

[0055] As an example, among the plurality of test samples prepared in step S1, there are test samples with 5 different K values, and the K value can be selected from any natural number between 0 and 8. Then, the 5 different K values of the test samples can include but are not limited to: 0, 1, 2, 3, 4; 1, 2, 3, 4, 5; 2, 3, 4, 5, 6; 3, 4, 5, 6, 7; 4, 5, 6, 7, 8; 0, 2, 4, 6, 8, etc. ​

[0056] In some embodiments, as Figure 2 As shown, the test sample includes a first protective cover 51, a capacitor core 40, and a second protective cover 52 arranged in sequence along the stacking direction Z. The capacitor core 40 is composed of a plurality of capacitor units 30 arranged along the stacking direction Z. The first protective cover 51 of the test sample is composed of m blank dielectric layers 23 arranged along the stacking direction Z. The second protective cover 52 of the test sample is composed of n blank dielectric layers 23 arranged along the stacking direction Z. Wherein, m and n are each independently selected from any positive integer not less than 5, and the absolute value of the difference between m and m is less than or equal to 2. Further, m and n are each independently selected from any positive integer between 5 and 50, such as 5, 10, 15, 20, 25, 30, 35, 40, 45 or 50. Further, m and n are each independently selected from any positive integer between 10 and 30.

[0057] In some embodiments, the thickness of each of the prepared multiple test samples is the same, that is, the total number of blank dielectric layers 23, first electrode layers 21, and second electrode layers 22 within each test sample is the same. For example, the total number of blank dielectric layers 23, first electrode layers 21, and second electrode layers 22 within each test sample is 40 to 80, such as 40, 45, 50, 55, 60, 65, 70, 75, or 80.

[0058] S2: Measure the total capacitance of each test sample.

[0059] If the test sample is Class 1 porcelain, its total capacitance can be measured with reference to the national standard GB / T21041-2007, "Fixed Capacitors for Electronic Equipment - Part 21: Sectional Specification - Class 1 Surface Mount Multilayer Ceramic Fixed Capacitors," which is equivalent to the International Electrotechnical Commission standard IEC60384-21. If the test sample is Class 2 porcelain, its total capacitance can be measured with reference to the national standard GB / T21042-2007, "Fixed Capacitors for Electronic Equipment - Part 22: Sectional Specification - Class 2 Surface Mount Multilayer Ceramic Fixed Capacitors," which is equivalent to the International Electrotechnical Commission standard IEC60384-22. Those skilled in the art can select an appropriate test method based on parameters such as the temperature characteristics of the test sample.

[0060] S3: Based on the total capacitance measured in step S2 and the number of capacitance units in each test sample, calculate the capacitance of a single capacitance unit corresponding to each K value; The total capacitance of the test sample is recorded as C total , the capacitance of the capacitor unit inside the test sample is recorded as C K Since the K value of the capacitor units inside the test sample is the same, it can be seen that the dielectric thickness D of each capacitor unit is the same, and the capacitance C of each capacitor unit is the same. KAlso same, then: C total = θ x C K .

[0061] Therefore, based on the total capacitance C total measured in step S2, the number θ of the capacitive units inside each test sample, and the corresponding K value, the capacitance C K of the capacitive unit corresponding to each K value is calculated, so as to obtain a plurality of groups of data composed of K, C K .

[0062] In some embodiments, after step S3, the following step is further included: based on the K value and the capacitance C K of each capacitive unit calculated in step S3, a functional relationship between the K value and the capacitance C K of the capacitive unit is fitted to calculate the capacitance of the capacitive unit corresponding to other K values.

[0063] According to the plurality of groups of data composed of K, C K , taking the K value as the independent variable and the C K as the dependent variable, the data processing software such as excel, origin, SPSS, etc. is used for fitting, so as to obtain a functional relationship between C K and the K value. By using the functional relationship, the capacitance C K of the capacitive unit corresponding to other K values can be predicted.

[0064] It can be understood that the other K values refer to the K values not included in the plurality of test samples prepared in step S1. For example, the K values of the plurality of test samples in step S1 are 0, 1, 2, and 3 respectively, and the nonlinear functional relationship can be used to predict the capacitance C K of a single capacitive unit when K>3.

[0065] Therefore, the types of test samples prepared in step S1 can be reduced, which plays a role in saving materials and labor, and the C K corresponding to different K values can be quickly and accurately obtained, so as to provide more choices for determining the structural parameters of the MLCC product, and the hit rate of the capacity of the MLCC product is further improved.

[0066] The K value and the capacitance C K of the capacitive unit are in a nonlinear relationship, and at least 3 groups of data composed of K, C K are required for fitting, so the plurality of test samples prepared in step S1 includes test samples with at least 3 different K values. The more different K values, the better the goodness of fit of the obtained functional relationship, and the closer the determination coefficient R 2 to 1.

[0067] In some embodiments, the functional relationship can be selected from any one of a quadratic function, a cubic function and a quartic function, provided that the coefficient of determination R 2 ≥0.98.

[0068] In some embodiments, the functional relationship is a polynomial function of multiple degrees with one variable, which has a coefficient of determination R 2 ≥0.98, such as 0.98, 0.985, 0.99, 0.995, 0.999, 0.9995, 0.9999 or 1. The polynomial function of multiple degrees with one variable refers to a polynomial function with one variable K and each term has a degree greater than 2. Further, the functional relationship can be a quartic polynomial function with one variable, which has an expression of C K =aK 4 +bK 3 +cK 2 +dK+e, where a, b, c, d and e are arbitrary constants, and a is not equal to 0.

[0069] S4: determining the structure parameters of the MLCC product according to the target capacitance, the target thickness and the capacitances of the plurality of capacitive units calculated in step S3, wherein the structure parameters include the number of the capacitive units corresponding to each K value and the arrangement order of the capacitive units in the stacking direction.

[0070] It can be understood that the structure parameters of the MLCC product in step S4 can include one or more, and a person skilled in the art can make further selection according to the actual production conditions, the stress distribution of the product, the current distribution of the product and the like, so as to obtain the MLCC product with high capacitance accuracy, high reliability and high stability.

[0071] In some embodiments, the MLCC product includes a first protective cover, a capacitive core and a second protective cover arranged in sequence in the stacking direction, the capacitive core is composed of a plurality of capacitive units arranged in the stacking direction, the first protective cover is composed of M blank dielectric layers arranged in the stacking direction, and the second protective cover is composed of N blank dielectric layers arranged in the stacking direction.

[0072] In step S4, the structure parameters of the MLCC product further include the values of M and N, wherein M and N are each independently selected from any integer not less than 5, and the absolute value of the difference between M and N is less than or equal to 2. Further, M and N are each independently selected from any integer between 5 and 20, and the absolute value of the difference between M and N is less than or equal to 1. Exemplarily, M and N are each independently selected from any one of 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20. Further, M and N are each independently selected from any integer between 5 and 12, such as M=N=5 or M=8 and N=9.

[0073] In the MLCC product, the first protective cover and the second protective cover cover the upper and lower surfaces of the capacitor core. By limiting the number deviation of the blank dielectric layers in the first protective cover and the second protective cover, the structure fixation, physical protection, environmental isolation and heat dissipation assistance can be improved, thereby improving the reliability, stability and service life of the MLCC product.

[0074] In some embodiments, in step S4, the arrangement order of each capacitor unit in the stacking direction satisfies: Taking the central axis of the stacking direction as a reference, the absolute value of the difference of the K value between the capacitor units equidistant from the central axis is not more than 5, for example, it can be 0, 1, 2, 3, 4 or 5, thereby balancing the internal stress.

[0075] It can be understood that the central axis of the stacking direction refers to the central axis of the capacitor core (or the MLCC product) in the stacking direction. If the total number of the first electrode layer, the second electrode layer and the blank dielectric layer in the capacitor core is odd, the central axis is located at the middle line position of the middlemost film layer; if the total number is even, the central axis is located at the interface position between the two middlemost film layers.

[0076] In addition, the central axis can also be determined by the following method: if the MLCC product has an odd number of capacitor units inside, the middlemost capacitor unit is regarded as the central axis; if the MLCC product has an even number of capacitor units inside, the first electrode layer or the second electrode layer shared by the two middlemost capacitor units is regarded as the central axis.

[0077] Further, the absolute value of the difference of the K value between the capacitor units equidistant from the central axis is not more than 2. In this way, the MLCC product as a whole presents a symmetrical structure or an approximate symmetrical structure, which is beneficial to balance the stress distribution inside the product and avoid ceramic body cracking caused by uneven stress distribution.

[0078] In some embodiments, in the direction pointing to the central axis, the K value of each capacitor unit is monotonically non-decreasing. That is, the K value of the capacitor unit close to the central axis is not lower than the K value of the capacitor unit far from the central axis.

[0079] In the case that the internal ceramic dielectric film or the blank dielectric layer has many defects and it is difficult to remove the defects, the K value is distributed in this way, which is beneficial to reduce the current in the central region, thereby reducing the temperature difference inside. At the same time, during the cooling process after high-temperature sintering, the shrinkage stress of the central region is higher than that of the edge region, and the K value is distributed in this way, which is also beneficial to avoid the generation of microcracks.

[0080] S5: Stack and assemble according to the structure parameters determined in step S4 to form an MLCC product.

[0081] In some embodiments, the stack assembly of the MLCC product comprises the following steps: (1) Stacking: stack the first electrode layer, the second electrode layer and the blank dielectric film together according to the structural parameters to form a bar with consistent thickness.

[0082] (2) Laminating: make the layers in the bar tightly combined with each other by hydrostatic pressure to improve the density of the ceramic body after sintering, so that they are more tightly combined together.

[0083] (3) Cutting: cut the laminated bar in horizontal and vertical directions according to the preset size by using a sheet-shaped thin blade to make it into completely separated independent chips (also known as capacitor green bodies).

[0084] (4) Gel removal: heat treat the capacitor green body to remove organic matter such as adhesive.

[0085] (5) Sintering: use an atmosphere sintering furnace to sinter the capacitor green body after gel removal at 1100°C to 1350°C to form a ceramic body with intact internal electrodes, high density, qualified size, high mechanical strength and excellent electrical properties.

[0086] (6) Chamfering: also known as grinding, put the ceramic body, water and chamfering balls in a chamfering tank, and move by ball milling and planetary milling, etc. to remove burrs on the surface of the ceramic body while chamfering, so that the surface is smooth and the internal electrodes of the end surface are fully exposed.

[0087] (7) End sealing: use an end sealing machine to coat end electrode paste on both ends of the chamfered ceramic body to connect the internal electrodes of the end surface and form an external electrode.

[0088] (8) End sintering: under high temperature conditions, the organic binder in the end electrode paste is fully burned, the glass powder is melted and infiltrates the copper powder, so that the end is solidified and forms a good connection with the ceramic body and the internal electrodes.

[0089] (9) Electroplating: in an electroplating solution containing nickel ions or tin ions, the end electrode is used as the cathode, and a certain low-voltage direct current is applied to continuously deposit a nickel layer or a tin layer on the surface of the cathode.

[0090] (10) Testing and inspection: test and sort the MLCC product 100% for capacity, loss, insulation and voltage resistance, and remove defective products. After sorting according to different capacity ranges, perform appearance morphology inspection.

[0091] In the second aspect, the application provides an MLCC product prepared by the method for preparing an MLCC product as described above. Thus, the MLCC product has the advantages of high capacity design precision and low preparation cost for various sizes and various capacity design requirements, and is very suitable for large-scale industrial application.

[0092] The following is further illustrated in combination with specific examples and comparative examples. The raw materials involved in the following specific examples and comparative examples, if not specifically stated, can be sourced from the market. The instruments used, if not specifically stated, can be sourced from the market. The processes involved, if not specifically stated, are routinely selected by those skilled in the art.

[0093] Examples The present example provides a method for testing the capacitance of a capacitor unit, which is as follows: (1) Five test samples were prepared.

[0094] Each test sample comprises 5 first electrode layers (denoted as A) and 5 second electrode layers (denoted as B) arranged alternately along the stacking direction. The first electrode layer and the second electrode layer each comprise a ceramic dielectric film and an internal electrode printed thereon, and the internal electrodes of the two are arranged in cross to form a capacitor unit. A continuous K number of blank dielectric layers are arranged between adjacent first electrode layers and second electrode layers.

[0095] Each test sample comprises a first protective cover, a capacitor core and a second protective cover arranged in sequence along the stacking direction. The first protective cover is composed of m blank dielectric layers arranged along the stacking direction, and the second protective cover is composed of n blank dielectric layers arranged along the stacking direction. The number of capacitor units is one less than the total number of first electrode layers and second electrode layers (i.e. 5x2-1), so the capacitor core is composed of 9 capacitor units arranged along the stacking direction. Therefore, the layer structure of each test sample can be represented as "m--(AKB)×5--n".

[0096] As shown in Table 2, the layer structure of the test sample is "23--(A0B)×5--22", which means that the first protective cover has 23 blank dielectric layers, the second protective cover has 22 blank dielectric layers, the capacitor core is composed of 5 first electrode layers and 5 second electrode layers arranged alternately, and forms 9 capacitor units, and the K value of each capacitor unit is 0, and the total number of layers is 55. Other layer structures are similar and will not be repeated here.

[0097] (2) The total capacitance C of each test sample was measured according to JIS C5101-21 total .

[0098] (3) According to the total capacitance C and the number of capacitor units inside each test sample, the capacitance of each capacitor unit C is calculated as follows: total total C = 9xC​K Calculate the capacitance value C of a single capacitor unit corresponding to each K value K , the results are listed in Table 2.

[0099] The K value is the independent variable, and the capacitance value C of a single capacitor unit is K As the dependent variable, we can use Excel to fit the following Figure 5 The expression of the univariate quartic polynomial function shown is: C K =0.0555K 4 -0.6036K 3 +2.5337K 2 -5.4578K+7.5556, its determination coefficient R 2 =1.

[0100] Using the above expression, the capacitance value C of a single capacitor unit when K>4 can be calculated: K .

[0101] Table 2. Capacitance data of test samples Comparative Example This comparative example uses a conventional method to calculate the capacitance of a capacitor unit, as follows: For the test samples prepared in the examples, the K '=(ε×8.854×S)÷D to calculate the theoretical capacitance C of the capacitor unit K ', and according to C total '=9×C K 'Calculate the theoretical total capacitance C of the test sample total '. Then, the total capacitance C of the test sample total The deviation η of the sum is: η=(C total -C total ')÷C total ×100%, the results are listed in Table 2.

[0102] The relative dielectric constant of the ceramic dielectric material used for the ceramic dielectric diaphragm and the blank dielectric layer is ε=23.36. The ceramic dielectric diaphragm and the blank dielectric layer are prepared by tape casting, with a thickness of d=11μm. The dielectric thickness of the capacitor unit is D=(K+1)×d. The cross area of ​​the inner electrodes of the first electrode layer and the second electrode layer is S=0.402mm. 2 .

[0103] As shown in Table 2, as the value of K increases, the capacitance C of each capacitor unit K And the theoretical capacitance C Kthe difference between the total capacitance C total and the theoretical total capacitance C total η is close to 20%. It can be seen that the capacity hit rate of the test product designed based on the inverse proportional relationship is extremely low, and repeated adjustment is needed to obtain a suitable test product and determine the structural parameters of the MLCC product. The whole process is complicated and complex, consumes a large amount of materials and labor, and has a high production cost.

[0104] Application Example According to the capacitance values C K of the capacitance units measured by the embodiment, the target capacitance and the target thickness of the MLCC product, the structural parameters of different MLCC products are determined. The structural parameters include the number of capacitance units corresponding to each K value, the arrangement order of each capacitance unit in the stacking direction, and the number of blank dielectric layers contained in the first protective cover and the second protective cover, so as to obtain the layer structure as shown in Table 3. Finally, according to the structural parameters of the MLCC product, the layers are composed to form a series of MLCC products.

[0105] As can be seen from Table 3, according to the five test samples, the structural parameters of the MLCC products with a target capacitance in the range of 8.0 pF~330 pF can be determined. Among them, the layer structure of the MLCC product numbered 12 is “4--(A0B)×11-A1B-(A0B)×11--4”, which means that in the stacking direction, there are 4 blank dielectric layers as the first protective cover, 11 first electrode layers and 11 second electrode layers arranged alternately, the first electrode layer, the blank dielectric layer and the second electrode layer arranged in turn, 11 first electrode layers and 11 second electrode layers arranged alternately, and 4 blank dielectric layers as the second protective cover. The layer structures of other numbered MLCC products are similar and will not be repeated here.

[0106] In summary, the embodiment can determine five K values and the capacitance of the corresponding capacitance units by five test samples, and at least multiple MLCC products with different target capacitances can be designed in the application example. While ensuring the capacity hit rate of the MLCC product, the production process is effectively simplified, the loss of materials and labor is avoided, and the production cost is significantly reduced.

[0107] Table 3. Target capacitance of MLCC product and corresponding layer design Any combination of the technical features in the above-described embodiments can be made, and for the sake of brevity, not all possible combinations are described, however, it is to be understood that the application encompasses all such possible combinations.

[0108] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the protection scope of the present application. It should be pointed out that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A method for manufacturing an MLCC product, characterized in that: The following steps are involved: S1: Prepare multiple test samples, each test sample comprising a plurality of first electrode layers and a plurality of second electrode layers alternately arranged along a stacking direction, wherein the first electrode layers and the second electrode layers each comprise a ceramic dielectric diaphragm and an inner electrode printed thereon, and the inner electrodes of the two layers are arranged crosswise to form a capacitor unit; K continuous blank dielectric layers are arranged between adjacent first electrode layers and second electrode layers, where K is a natural number, and for each test sample, the K value of all capacitor units within the sample is the same; the prepared multiple test samples include test samples having a variety of different K values; S2: measuring the total capacitance of each test sample; S3: Based on the total capacitance measured in step S2 and the number of capacitance units inside each test sample, calculate the capacitance of the capacitance unit corresponding to each K value; S4: Determine structural parameters of the MLCC product based on the target capacitance and target thickness of the MLCC product and the capacitance of each capacitor unit calculated in step S3, wherein the structural parameters include the number of capacitor units corresponding to each K value and the arrangement order of each capacitor unit in the stacking direction; S5: Lamination assembly is performed according to the structural parameters determined in step S4 to form the MLCC product.

2. The method for manufacturing an MLCC product according to claim 1, wherein: The MLCC product includes a first protective cover, a capacitor core, and a second protective cover arranged in sequence along the stacking direction. The capacitor core is composed of a plurality of capacitor units arranged along the stacking direction. The first protective cover is composed of M blank dielectric layers arranged along the stacking direction. The second protective cover is composed of N blank dielectric layers arranged along the stacking direction. In step S4, the structural parameters further include the values ​​of M and N, wherein M and N are each independently selected from any integer not less than 5, and the absolute value of the difference between M and N is less than or equal to 2.

3. The method for manufacturing an MLCC product according to claim 2, wherein: In step S4, the arrangement order of the capacitor units in the stacking direction satisfies: Taking the central axis in the stacking direction as a reference, the absolute value of the difference in K value between capacitor units that are equidistant from the central axis does not exceed 5.

4. The method for manufacturing an MLCC product according to claim 1, wherein: The prepared multiple test samples include test samples with at least 3 different K values.

5. The method for manufacturing an MLCC product according to claim 1, wherein: The number of capacitor units in the same test sample is not less than 3.

6. The method for manufacturing an MLCC product according to any one of claims 1 to 5, wherein: The K value is selected from any natural number between 0 and 8.

7. The method for manufacturing an MLCC product according to any one of claims 1 to 5, wherein: After step S3, the following steps are further included: Based on the K value and the capacitance of each capacitor unit calculated in step S3 , a functional relationship between the K value and the capacitance of the capacitor unit is obtained by fitting to calculate the capacitance of the capacitor unit corresponding to other K values.

8. The method for manufacturing an MLCC product according to claim 7, wherein: The functional relationship is a univariate multi-time polynomial function, and its determination coefficient R 2 ≥0.

98.

9. The method for manufacturing an MLCC product according to claim 1, wherein: The ceramic dielectric diaphragms and the blank dielectric layers are both prepared by tape casting, and the thicknesses of the ceramic dielectric diaphragms and the blank dielectric layers are consistent.

10. An MLCC product, characterized in that: The MLCC product is manufactured using the manufacturing method of any one of claims 1 to 9.

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