Sintering method of multilayer ceramic capacitor

Abstract

The invention belongs to the field of electronic component manufacturing, and particularly discloses a sintering method of a multilayer ceramic capacitor, which comprises the following steps of: carrying out trial sintering on a laminated green body after glue removal according to a sintering curve to obtain an oxygen consumption-temperature curve, and taking the oxygen consumption as a reference oxygen consumption at a corresponding temperature; formal sintering is carried out on the stacked green bodies after glue discharging according to a sintering curve, and the sintering atmosphere is adjusted according to the variable quantity of the real-time oxygen consumption and the standard oxygen consumption; the sintering atmosphere contains inert gas, hydrogen and water vapor. According to the sintering method, the sintering atmosphere composition and the gas flow in the formal sintering step can be regulated and controlled in real time, so that the stability of fluidity, oxidability and the like of the sintering atmosphere in the formal sintering process is ensured, the oxidized amount of the Ni element in the MLCC product is controlled, the electrical performance and the reliability of the prepared MLCC product are improved, and the production cost is reduced. Meanwhile, the equipment utilization rate is increased, the productivity is increased, and the cost is reduced.

Description

Technical Field

[0001] The invention belongs to the field of electronic component manufacturing, and in particular relates to a sintering method for a multilayer ceramic capacitor. Background Art

[0002] Multilayer ceramic capacitors (MLCCs) are widely used in computers, mobile electronic devices, and new energy vehicle electronic devices due to their small size, high capacitance, and easy installation. Generally, the method for manufacturing multilayer ceramic capacitors includes: manufacturing ceramic green sheets, printing internal electrode layers on ceramic green sheets, and then stacking and cutting the ceramic green sheets with internal electrode layers to form laminated green sheets, sintering the laminated green sheets at high temperature to form ceramic chips, and preparing external electrodes at both ends of the ceramic chips to finally form multilayer ceramic capacitors.

[0003] The existing technology often uses a slow heating rate when sintering the stacked green body, which leads to a long production cycle of multilayer ceramic capacitors and difficulty in improving production efficiency. Accelerating the heating rate will cause the reaction volume to increase exponentially, and the fluidity and substitution of the reaction atmosphere will be weakened, resulting in the deterioration of the microstructure of the sintered ceramic chip, which in turn leads to the degradation of product reliability. Summary of the invention

[0004] In order to overcome at least one technical problem existing in the above-mentioned prior art, one of the objectives of the present invention is to provide a sintering method for a multilayer ceramic capacitor.

[0005] A second object of the present invention is to provide a multilayer ceramic capacitor.

[0006] A third object of the present invention is to provide a sintering method for the above-mentioned multilayer ceramic capacitor and / or application of the above-mentioned multilayer ceramic capacitor in the field of electronic products.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A first aspect of the present invention provides a sintering method for a multilayer ceramic capacitor, comprising the following steps:

[0009] The stacked green compacts after debinding are trial-sintered according to the sintering curve to obtain an oxygen consumption-temperature curve, wherein the oxygen consumption is used as a reference oxygen consumption at a corresponding temperature; the stacked green compacts after debinding are formally sintered according to the sintering curve, and the sintering atmosphere is adjusted according to the change in the real-time oxygen consumption and the reference oxygen consumption;

[0010] The sintering atmosphere contains inert gas, hydrogen and water vapor.

[0011] In some embodiments of the present invention, the step of adjusting the sintering atmosphere according to the change in the real-time oxygen consumption and the reference oxygen consumption is:

[0012] When the real-time oxygen consumption increases by 1% compared with the reference oxygen consumption, the real-time gas flow rate of the sintering atmosphere increases by 1.25% to 2% compared with the initial gas flow rate; the real-time volume percentage of hydrogen increases by 1.5% to 2% compared with the initial volume percentage of hydrogen;

[0013] When the real-time oxygen consumption decreases by 1% compared with the reference oxygen consumption, the real-time gas flow of the sintering atmosphere decreases by 1.25% to 2% compared with the initial gas flow; the real-time volume percentage of hydrogen decreases by 1.5% to 2% compared with the initial volume percentage of hydrogen.

[0014] The sintering method in the present invention has a great influence on the performance of the product after sintering, and the oxidizing property of the sintering atmosphere should be ensured to be suitable during sintering. When the oxidizing property of the sintering atmosphere is too strong, the Ni electrode will be oxidized, and the electrical performance of the product will deteriorate. When the reducibility is too strong, the dielectric oxygen vacancies of the laminated green body will be too many, the dielectric will become semiconductive, and the insulation will decrease. Therefore, it is necessary to adjust the gas flow rate and atmosphere composition of the sintering atmosphere according to the change in the real-time oxygen consumption and the reference oxygen consumption. In the traditional sintering process, the oxidizing property of the atmosphere in the sintering furnace is not monitored in real time, and there is also a lack of effective guidance for the real-time regulation of the sintering atmosphere. In the high-speed sintering process, the high heating rate leads to a high reaction amount, which in turn leads to a sudden change in the atmosphere composition around the laminated green body, which has a great influence on the performance of the product after sintering. Therefore, the above-mentioned disadvantages of not being able to detect and regulate in real time are more obvious in the high-speed sintering process.

[0015] In some embodiments of the present invention, the real-time volume percentage of water vapor in the sintering atmosphere is the same as the initial volume percentage of water vapor.

[0016] In some embodiments of the present invention, the oxygen consumption in the oxygen consumption-temperature curve refers to the oxygen concentration when the sintering furnace is in an empty furnace state minus the real-time oxygen concentration during trial sintering.

[0017] In some embodiments of the present invention, the oxygen concentration is detected by an oxygen concentration detection device disposed in the sintering furnace.

[0018] In some embodiments of the present invention, the real-time oxygen consumption refers to the difference between the initial oxygen concentration and the real-time oxygen concentration in the formal sintering step. In the formal sintering process, the present invention monitors the real-time oxygen consumption of the entire formal sintering process through an oxygen concentration detection device arranged in the sintering furnace, which can reflect the oxidizing property of the sintering atmosphere in real time; the sintering atmosphere gas flow rate and hydrogen concentration are regulated according to the change in the real-time oxygen consumption relative to the reference oxygen consumption, and the atmosphere composition around the stacked green body can be replenished in time when it changes suddenly, so as to ensure the stability of the oxidizing property of the atmosphere, thereby ensuring the performance of the MLCC product.

[0019] In some embodiments of the present invention, when the real-time oxygen consumption increases by 1% compared with the baseline oxygen consumption, the increase in the real-time gas flow rate of the sintering atmosphere compared with the initial gas flow rate can be selected from 1.25%, 1.3%, 1.35%, 1.4%, 1.45%, 1.5%, 1.55%, 1.6%, 1.65%, 1.7%, 1.75%, 1.8%, 1.85%, 1.9%, 1.95% or 2%.

[0020] In some embodiments of the present invention, when the real-time oxygen consumption decreases by 1% compared with the baseline oxygen consumption, the amount by which the real-time gas flow rate of the sintering atmosphere is reduced compared with the initial gas flow rate can be selected from 1.25%, 1.3%, 1.35%, 1.4%, 1.45%, 1.5%, 1.55%, 1.6%, 1.65%, 1.7%, 1.75%, 1.8%, 1.85%, 1.9%, 1.95% or 2%.

[0021] In some embodiments of the present invention, when the real-time oxygen consumption increases by 1% compared with the baseline oxygen consumption, the increase in the real-time volume percentage of hydrogen compared with the initial volume percentage of hydrogen can be selected from 1.5%, 1.55%, 1.6%, 1.65%, 1.7%, 1.75%, 1.8%, 1.85%, 1.9%, 1.95% or 2%.

[0022] In some embodiments of the present invention, when the real-time oxygen consumption decreases by 1% compared with the baseline oxygen consumption, the amount by which the real-time volume percentage of hydrogen decreases compared to the initial volume percentage of hydrogen can be selected from 1.5%, 1.55%, 1.6%, 1.65%, 1.7%, 1.75%, 1.8%, 1.85%, 1.9%, 1.95% or 2%.

[0023] In some embodiments of the present invention, the initial air flow rate is 500-1400 L / min; for example, it can be selected from 500 L / min, 600 L / min, 700 L / min, 800 L / min, 900 L / min, 1000 L / min, 1100 L / min, 1200 L / min, 1300 L / min or 1400 L / min.

[0024] In some embodiments of the present invention, the sintering atmosphere is composed of an inert gas, hydrogen and water vapor. In some embodiments of the present invention, in the sintering atmosphere, the initial volume percentage of hydrogen is 0.06% to 0.5%, the initial volume percentage of water vapor is 6% to 18%; and the inert gas is the balance.

[0025] In some embodiments of the present invention, the inert gas is selected from at least one of nitrogen and argon.

[0026] In some embodiments of the present invention, the initial volume percentage of hydrogen is 0.06% to 0.5%, for example, can be selected from 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45% or 0.5%.

[0027] In some embodiments of the present invention, the initial volume percentage of water vapor in the sintering atmosphere is 6% to 18%, for example, can be selected from 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17% or 18%.

[0028] In some embodiments of the present invention, the real-time airflow rate does not change by more than 80% compared with the initial airflow rate. For example, the rate of change can be selected from 0%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 79.99%.

[0029] In some embodiments of the present invention, the real-time volume percentage of hydrogen changes by no more than 80% compared with the initial volume percentage of hydrogen. For example, the change rate can be selected from 0%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 79.99%.

[0030] In some embodiments of the present invention, the sintering curve is: firstly heating to 850-1000°C and keeping warm for 2-20 minutes (i.e., the first sintering stage); then heating to 1180-1280°C and keeping warm for 2-90 minutes (i.e., the second sintering stage). The time required for the formal sintering process of the present invention is relatively short (less than 2 hours), which can achieve the purpose of rapid sintering, significantly reduce costs, and improve production efficiency.

[0031] In some embodiments of the present invention, the sintering curve is: heating from 10 to 40°C to 850 to 1000°C at a heating rate of 30 to 130°C / min and then keeping warm for 2 to 20 minutes (i.e., the first sintering stage); then heating to 1180 to 1280°C at a heating rate of 100 to 3000°C / min and keeping warm for 2 to 90 minutes (i.e., the second sintering stage).

[0032] In some embodiments of the present invention, the heating rate of the first sintering stage is 30-130°C / min, for example, can be selected from: 30°C / min, 40°C / min, 50°C / min, 60°C / min, 70°C / min, 80°C / min, 90°C / min, 100°C / min, 110°C / min, 120°C / min or 130°C / min.

[0033] In some embodiments of the present invention, the holding temperature of the first sintering stage is 850-1000°C, for example, can be selected from 850°C, 860°C, 870°C, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C, 940°C, 950°C, 960°C, 970°C, 980°C, 990°C or 1000°C.

[0034] In some embodiments of the present invention, the holding time of the first sintering stage is 2 to 20 min, for example, can be selected from 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min or 20 min.

[0035] In some embodiments of the present invention, the heating rate of the second sintering stage is 100 to 3000°C / min, for example, can be selected from 100°C / min, 200°C / min, 400°C / min, 600°C / min, 800°C / min, 1000°C / min, 1200°C / min, 1400°C / min, 1600°C / min, 1800°C / min, 2000°C / min, 2200°C / min, 2400°C / min, 2600°C / min, 2800°C / min or 3000°C / min.

[0036] In some embodiments of the present invention, the holding temperature of the second sintering stage is 1180-1280°C, for example, can be selected from 1180°C, 1190°C, 1200°C, 1210°C, 1220°C, 1230°C, 1240°C, 1250°C, 1260°C, 1270°C or 1280°C.

[0037] In some embodiments of the present invention, the holding time of the second sintering stage is 2 to 90 min, for example, can be selected from 2 min, 5 min, 8 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min or 90 min.

[0038] The present invention sets the sintering curve as a two-stage sintering, which can significantly reduce the amount of carbon deposits in the MLCC product during high-speed sintering, reduce the impact of carbon deposits on the insulation of the product, remove residual carbon deposits in the first sintering stage (sintering at 850-1000°C), ensure the insulation of the product, improve the performance of the MLCC product obtained by the sintering method of the present invention, and also ensure production efficiency.

[0039] In some embodiments of the present invention, the number of stacked green compacts in the trial sintering step is 1000 to 30000, for example, can be selected from 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000, 16000, 17000, 18000, 19000, 20000, 21000, 22000, 23000, 24000, 25000, 26000, 27000, 28000, 29000 or 30000.

[0040] In some embodiments of the present invention, the number of stacked green bodies in the formal sintering step is 10,000 to 300,000, for example, can be selected from 10,000, 20,000, 30,000, 40,000, 50,000, 60,000, 70,000, 80,000, 90,000, 100,000, 110,000, 120,000, 130,000, 140,000, 150,000, 160,000, 170,000, 180,000, 190,000, 200,000, 210,000, 220,000, 230,000, 240,000, 250,000, 260,000, 270,000, 280,000, 290,000 or 300,000.

[0041] The oxygen consumption-temperature curve and the corresponding reference oxygen consumption data obtained through a trial sintering of the present invention can be used to guide the formal sintering of multiple batches of stacked green compacts. Therefore, the trial sintering step of the present invention does not require too many samples and will not cause waste of materials.

[0042] In some embodiments of the present invention, the sintering method of the present invention further comprises a step of cooling the temperature by natural cooling after the formal sintering step.

[0043] In some embodiments of the present invention, the laminated green body is prepared by a preparation method comprising the following steps: casting a ceramic slurry into a film to obtain a ceramic green sheet; then printing an internal electrode slurry on the ceramic green sheet, and then laminating and pressing to obtain the laminated green body.

[0044] The second aspect of the present invention provides a multilayer ceramic capacitor, comprising a ceramic chip; the ceramic chip is made using the sintering method described in the first aspect of the present invention; the ceramic chip contains nickel and nickel oxide; the molar amount of nickel oxide is 1%-2% of the total molar amount of nickel and nickel oxide.

[0045] In some embodiments of the present invention, the molar amount of oxidized Ni element in the multilayer ceramic capacitor is 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2% of the total molar amount of Ni element.

[0046] The third aspect of the present invention provides a sintering method of the multilayer ceramic capacitor described in the first aspect of the present invention and / or an application of the multilayer ceramic capacitor described in the second aspect of the present invention in the field of electronic products.

[0047] The beneficial effect of the present invention is that the sintering method of the present invention can regulate the sintering atmosphere composition and gas flow rate of the formal sintering step in real time, thereby ensuring the stability of the fluidity, oxidizability, etc. of the sintering atmosphere during the formal sintering process, and then controlling the amount of Ni element oxidized in the MLCC product, thereby improving the electrical properties and reliability of the prepared MLCC product, while improving equipment utilization, increasing production capacity, and reducing costs.

[0048] In addition, the sintering method of the present invention can achieve rapid sintering, and can complete the sintering of 10,000 to 300,000 stacked green compacts within 2 hours. The electrical performance and reliability of the sintered MLCC products are relatively high, and the failure rate is less than 1%. DETAILED DESCRIPTION

[0049] The specific implementation of the present invention is further described in detail below in conjunction with examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that if there are processes that are not particularly described in detail below, they can be implemented or understood by those skilled in the art with reference to the prior art. The reagents or instruments used that do not indicate the manufacturer are all conventional products that can be purchased commercially.

[0050] Example 1

[0051] This example provides a method for preparing a multilayer ceramic capacitor, comprising the following steps:

[0052] (1) mixing barium titanate powder, polyvinyl butyral (PVB), pineol and 2-ethylhexanoic acid in a mass ratio of barium titanate:PVB:pineol:2-ethylhexanoic acid = 3.5:5.5:1:0.1, and ball milling to obtain a ceramic slurry, then casting the ceramic slurry into a film, and drying to obtain a ceramic green sheet;

[0053] (2) nickel powder, ethyl cellulose, pinene alcohol and 2-(11-methyldodecyloxy)ethanol phosphate are uniformly mixed according to the mass ratio of nickel powder: ethyl cellulose: pinene alcohol: 2-(11-methyldodecyloxy)ethanol phosphate = 6.5:2.5:1:0.1 to obtain an internal electrode slurry, and the internal electrode slurry is printed on the ceramic green sheet obtained in step (1), and after drying, an internal electrode layer is formed on the ceramic green sheet;

[0054] (3) stacking, pressing, and cutting the ceramic green sheets with the internal electrode layers formed thereon to obtain a stacked green body;

[0055] (4) placing the obtained laminated green body into a debinding furnace for debinding treatment, heating the temperature to 600°C at a heating rate of 20°C / min, keeping the temperature for 5 hours, and then cooling naturally to room temperature;

[0056] (5) The debinded laminated green bodies are sintered according to the high-speed sintering method of this example to obtain ceramic chips.

[0057] The high-speed sintering method in this example is as follows: first, a single-layer 5,000-piece stacked green body sample is used for trial sintering to determine the reference oxygen consumption curve, that is, a curve constructed with temperature as the horizontal axis and oxygen consumption as the vertical axis, and then the sintering temperature-time curve (i.e., sintering curve) is kept unchanged (i.e., the heating rate, holding temperature, and holding time are unchanged), and a total of 10,000 stacked green bodies in two layers are formally sintered. After sintering, the temperature is reduced to room temperature (25°C) by natural cooling or other methods.

[0058] The sintering temperature-time curves of the trial sintering and the formal sintering are the same, both of which include the first sintering stage and the second sintering stage. Specifically, the first sintering stage: heating from room temperature (25°C) to 850°C at a heating rate of 30°C / min, and keeping warm for 10 minutes; the second sintering stage: heating from 850°C to 1180°C at a heating rate of 100°C / min, and keeping warm for 90 minutes.

[0059] The sintering atmosphere during the trial sintering was as follows: gas flow rate 700 L / min; in the sintering atmosphere, the volume percentage of hydrogen was 0.12%, the volume percentage of water vapor was 15%, and the balance was nitrogen.

[0060] During formal sintering, the initial gas flow rate is 700L / min, and the initial sintering atmosphere composition (i.e., hydrogen, water vapor, and nitrogen content) is the same as the sintering atmosphere composition of the trial sintering. During the formal sintering process, the gas flow rate and sintering atmosphere composition of the sintering atmosphere are adjusted according to the change value of the reference oxygen consumption at the corresponding temperature on the real-time oxygen consumption and the reference oxygen consumption curve. Specifically, for every 1% increase (or decrease) in the real-time oxygen consumption relative to the reference oxygen consumption, the sintering atmosphere gas flow rate increases (or decreases) by 1.25% relative to the initial gas flow rate, the hydrogen concentration increases (or decreases) by 1.5% relative to the initial hydrogen concentration, the volume percentage of water vapor remains unchanged at 15%, and the remainder is nitrogen.

[0061] (6) The ceramic chip is chamfered, coated with external electrode slurry and fired to obtain the multilayer ceramic capacitor.

[0062] Example 2

[0063] The preparation method of the multilayer ceramic capacitor in this example is different from that in Example 1 only in that: during the formal sintering in this example, according to the change in oxygen consumption at this time relative to the baseline oxygen consumption, for every 1% increase (or decrease) in oxygen consumption relative to the baseline oxygen consumption, the sintering atmosphere gas flow rate increases (or decreases) by 1.6% relative to the initial gas flow rate, and the hydrogen concentration increases (or decreases) by 1.7% relative to the initial hydrogen concentration, as shown in Table 1.

[0064] Example 3

[0065] The preparation method of the multilayer ceramic capacitor in this example is different from that in Example 1 only in that: during the formal sintering in this example, according to the change in oxygen consumption at this time relative to the baseline oxygen consumption, for every 1% increase (or decrease) in oxygen consumption relative to the baseline oxygen consumption, the sintering atmosphere gas flow rate increases (or decreases) by 2% relative to the initial gas flow rate, and the hydrogen concentration increases (or decreases) by 2% relative to the initial hydrogen concentration, as shown in Table 1.

[0066] Embodiments 4 to 6

[0067] The preparation method of the multilayer ceramic capacitor in Examples 4 to 6 is different from that in Example 1 only in that the sintering temperature-time curves used in the trial sintering and formal sintering of Examples 4 to 6 (i.e., the heating rate, holding time, and holding temperature of the first sintering stage and the second sintering stage) are different from those of Example 1, but the sintering temperature-time curves of the trial sintering and formal sintering in the same example are the same, as shown in Table 2.

[0068] Embodiments 7 to 9

[0069] The preparation method of the multilayer ceramic capacitor in Examples 7 to 9 is different from that in Example 1 only in that the initial gas flow rate and the sintering atmosphere composition of the trial sintering and formal sintering in Examples 7 to 9 are different from those in Example 1. However, in the same example, the initial gas flow rate and the composition of the initial sintering atmosphere in the formal sintering are exactly the same as those in the trial sintering, as shown in Table 3 below.

[0070] Example 10

[0071] The preparation method of the multilayer ceramic capacitor in this example is different from that in Example 1 only in that: in this example, 30,000 stacked green samples are used for trial sintering to determine the baseline oxygen consumption, and then 100,000 stacked green samples are formally sintered. In addition, the sintering temperature-time curve used in this example (i.e., the heating rate, holding time, and holding temperature of the first sintering stage and the second sintering stage) is different from that of Example 1, as shown in Table 2.

[0072] Embodiment 11

[0073] The method for preparing the multilayer ceramic capacitor in this example is different from that in Example 1 only in that in this example, 1000 stacked green samples are trial-sintered to determine the reference oxygen consumption, and then 10,000 stacked green samples are formally sintered.

[0074] Example 12

[0075] The method for preparing the multilayer ceramic capacitor in this example is different from that in Example 1 only in that in this example, 5000 stacked green samples are trial-sintered to determine the reference oxygen consumption, and then 30000 stacked green samples are formally sintered.

[0076] Comparative Example 1

[0077] The method for preparing the multilayer ceramic capacitor in this example is different from that in Example 1 only in that during the formal sintering in this example, the gas flow rate and hydrogen concentration are not adjusted according to the reference oxygen consumption, as shown in Table 1.

[0078] Comparative Example 2

[0079] The preparation method of the multilayer ceramic capacitor in this example is different from that in Example 1 only in that: during the formal sintering in this example, according to the change in oxygen consumption at this time relative to the baseline oxygen consumption, for every 1% increase (or decrease) in oxygen consumption relative to the baseline oxygen consumption, the sintering atmosphere gas flow rate increases (or decreases) by 0.5% relative to the initial gas flow rate, and the hydrogen concentration increases (or decreases) by 1.5% relative to the initial hydrogen concentration, as shown in Table 1.

[0080] Comparative Example 3

[0081] The preparation method of the multilayer ceramic capacitor in this example is different from that in Example 1 only in that: during the formal sintering in this example, according to the change in oxygen consumption at this time relative to the baseline oxygen consumption, for every 1% increase (or decrease) in oxygen consumption relative to the baseline oxygen consumption, the sintering atmosphere gas flow rate increases (or decreases) by 1.25% relative to the initial gas flow rate, and the hydrogen concentration increases (or decreases) by 0.5% relative to the initial hydrogen concentration, as shown in Table 1.

[0082] Comparative Example 4

[0083] The preparation method of the multilayer ceramic capacitor in this example is different from that in Example 1 only in that: during the formal sintering in this example, according to the change in oxygen consumption at this time relative to the baseline oxygen consumption, for every 1% increase (or decrease) in oxygen consumption relative to the baseline oxygen consumption, the sintering atmosphere gas flow rate increases (or decreases) by 1.25% relative to the initial gas flow rate, and the hydrogen concentration increases (or decreases) by 2.5% relative to the initial hydrogen concentration, as shown in Table 1.

[0084] Comparative Example 5

[0085] The preparation method of the multilayer ceramic capacitor in this example is different from that in Example 1 only in that: in this example, the first sintering stage is not set, and the temperature is directly increased from room temperature to 1180° C. at a heating rate of 100° C. / min and kept at this temperature for 90 minutes.

[0086] Table 1 Gas flow rate and hydrogen concentration adjustment parameters

[0087] Air flow adjustment amount / % Hydrogen concentration adjustment amount / % Example 1 1.25 1.5 Example 2 1.6 1.7 Example 3 2 2 Comparative Example 1 0 0 Comparative Example 2 0.5 1.5 Comparative Example 3 1.25 0.5 Comparative Example 4 1.25 2.5

[0088] Table 2 Parameters of the first sintering stage and the second sintering stage

[0089]

[0090]

[0091] Table 3 Initial gas flow and sintering atmosphere parameters

[0092]

[0093] Performance Test:

[0094] The various properties of the multilayer ceramic capacitors prepared by the preparation methods in Examples 1 to 12 and Comparative Examples 1 to 5 were tested respectively according to the following test methods. The specific test methods are as follows:

[0095] (1) Ni oxidation degree test: The Ni oxidation degree of the sample is tested by X-ray energy dispersive spectrometry (EDS). The Ni oxidation degree between 1% and 2% is considered qualified.

[0096] (2) Insulation resistance test: Apply a voltage of 4KV / mm in the resistance tester and record the resistance data. The specifications of the multilayer ceramic capacitors prepared in Examples 1 to 11 of the present invention and Comparative Examples 1 to 5 are 0603 specifications, and a resistance higher than 1GΩ is considered qualified; the specifications of the multilayer ceramic capacitors prepared in Example 12 are 0402 specifications, and a resistance higher than 5GΩ is considered qualified; the specifications of the multilayer ceramic capacitors prepared in Example 13 are 0805 specifications, and a resistance higher than 0.5GΩ is considered qualified.

[0097] (3) Long-term reliability test: 1,000 MLCC products are soldered to a circuit board and inserted into a high-temperature and high-humidity aging chamber for testing. The test voltage is the rated voltage and the test temperature is the rated temperature. After 1,000 hours of testing, the number of failed products is counted. A failure rate of less than 1% is considered qualified.

[0098] The performance data of the multilayer ceramic capacitors prepared by the preparation methods in Examples 1 to 12 and Comparative Examples 1 to 5 measured by the above test method are shown in Table 4.

[0099] Table 4 Performance data of multilayer ceramic capacitors

[0100]

[0101]

[0102] As shown in Table 4, Examples 1 to 12 of the present invention adopt a two-stage sintering process, and adjust and control the flow rate and composition of the sintering atmosphere during the formal sintering process according to the oxygen consumption during the trial sintering process, so as to ensure that the high-speed sintered product has a Ni oxidation degree of 1 to 2%, qualified insulation resistance and a failure rate of less than 1% during high-speed sintering. Comparative Example 1 does not adjust the flow rate and composition of the sintering atmosphere in the formal sintering stage according to the reference oxygen consumption, and the gas flow adjustment amount of Comparative Example 2 is too low, both of which will lead to unqualified insulation resistance and poor product reliability (i.e., failure rate>1%); the hydrogen concentration adjustment amount of Comparative Example 3 is too low, the oxidizing property of the sintering atmosphere becomes stronger, resulting in a high Ni oxidation degree; the hydrogen concentration adjustment amount of Comparative Example 4 is too high, resulting in unqualified insulation resistance and reduced product reliability; Comparative Example 5 does not set the first sintering stage, directly rises from room temperature to 1180°C at a heating rate of 100°C / min, and keeps warm for 50 minutes, resulting in a high carbon deposit content in the product, unqualified insulation resistance, and a significant decrease in product reliability.

[0103] In summary, the sintering method of the present invention is to first conduct trial sintering on a small batch of products to obtain a benchmark oxygen consumption, and guide the airflow control of the formal sintering, which can ensure the fluidity and replaceability of the reaction atmosphere during high-speed sintering, thereby achieving reaction volume control and avoiding the deterioration of the electrical properties and reliability of MLCC products. At the same time, it improves equipment utilization, increases production capacity, and reduces costs.

[0104] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A sintering method for a multilayer ceramic capacitor, characterized in that: The following steps are involved: The stacked green compact after debinding is trial-sintered according to the sintering curve to obtain an oxygen consumption-temperature curve, wherein the oxygen consumption is used as the reference oxygen consumption at the corresponding temperature; The stacked green compact after debinding is formally sintered according to the sintering curve, and the sintering atmosphere is adjusted according to the change of the real-time oxygen consumption and the reference oxygen consumption; The sintering atmosphere contains inert gas, hydrogen and water vapor.

2. The sintering method of a multilayer ceramic capacitor according to claim 1, characterized in that: The step of adjusting the sintering atmosphere according to the change in the real-time oxygen consumption and the benchmark oxygen consumption is as follows: when the real-time oxygen consumption increases or decreases by 1% compared with the benchmark oxygen consumption, the real-time gas flow rate of the sintering atmosphere increases or decreases by 1.25% to 2% compared with the initial gas flow rate; the real-time volume percentage of hydrogen increases or decreases by 1.5% to 2% compared with the initial volume percentage of hydrogen.

3. The sintering method of a multilayer ceramic capacitor according to claim 2, wherein: The initial gas flow rate is 500-1400 L / min.

4. The sintering method of a multilayer ceramic capacitor according to claim 2, wherein: In the sintering atmosphere, the initial volume percentage of hydrogen is 0.06% to 0.5%; the initial volume percentage of water vapor is 6% to 18%.

5. The sintering method of a multilayer ceramic capacitor according to claim 2, wherein: The change rate of the real-time gas flow rate compared with the initial gas flow rate does not exceed 80%; and / or the change rate of the real-time volume percentage of hydrogen compared with the initial volume percentage of hydrogen does not exceed 80%.

6. The sintering method of a multilayer ceramic capacitor according to claim 1, wherein: The sintering curve is: firstly heating to 850-1000° C. and keeping the temperature for 2-20 minutes; then heating to 1180-1280° C. and keeping the temperature for 2-90 minutes.

7. The sintering method of a multilayer ceramic capacitor according to claim 6, wherein: The sintering curve is: heating from 10 to 40°C to 850 to 1000°C at a heating rate of 30 to 130°C / min and then keeping the temperature for 2 to 20 minutes; then heating to 1180 to 1280°C at a heating rate of 100 to 3000°C / min and then keeping the temperature for 2 to 90 minutes.

8. The sintering method of a multilayer ceramic capacitor according to claim 1, wherein: The number of stacked green compacts in the trial sintering step is 1,000 to 30,000; And / or, the number of stacked green compacts in the formal sintering step is 10,000 to 300,000.

9. A multilayer ceramic capacitor, characterized in that: It comprises a ceramic chip; the ceramic chip is made by the sintering method according to any one of claims 1 to 8; the ceramic chip contains nickel and nickel oxide; the molar amount of the nickel oxide is 1%-2% of the total molar amount of nickel and nickel oxide.

10. A sintering method for a multilayer ceramic capacitor according to any one of claims 1 to 8 and / or use of the multilayer ceramic capacitor according to claim 9 in the field of electronic products.

Images