Method for monitoring the sintering consistency of aluminum nitride ceramics

Abstract

The application relates to the technical field of consistency monitoring, and particularly discloses a monitoring method for the sintering consistency of aluminum nitride ceramics, which comprises the following steps: step S1: taking green sheets of the same batch as the products to be sintered, processing through holes and filling with homologous metal paste, printing a center circular mark with a preset diameter through silk screen printing, and then performing isostatic pressing, laminating and cutting to obtain standard sample green bodies which are homogenous in material, density and graphic features with the products, so that the sintering shrinkage rules of the standard sample green bodies are consistent with those of the products; step S2: placing a plurality of standard sample green bodies in the same furnace as the products to be sintered, and performing glue removal and high-temperature sintering according to the same process to obtain sintered standard parts; and step S3: measuring the diameters of the center circular marks on the sintered standard parts, wherein the ratio of the diameters to the preset diameter is the shrinkage rate, and the sintering consistency of the batch is judged according to the fluctuation values of the shrinkage rates of the different sintered standard parts, so that the quantitative control of the uniformity of the temperature field in the furnace and the batch stability is realized.

Description

Technical Field

[0001] This invention relates to the field of consistency monitoring technology, and specifically to a method for monitoring the sintering consistency of aluminum nitride ceramics. Background Technology

[0002] Aluminum nitride ceramics, with their high thermal conductivity of 170–260 W / (m·K), excellent insulation properties, and thermal expansion coefficient matching that of silicon, have become the preferred material for packaging substrates of high-power integrated circuits, LEDs, and microwave devices.

[0003] With the surge in demand for high-power-density packaging in high-end fields such as 5G communication, new energy vehicles, and aerospace, the requirements for batch consistency and reliability of AlN ceramic substrates are becoming increasingly stringent. Sintering is typically carried out at high temperatures above 1800℃ in a reducing nitrogen atmosphere. The uniformity and stability of the temperature directly determine grain development, grain boundary phase composition, and density, thus affecting the product's heat dissipation capacity and mechanical reliability.

[0004] However, in actual production, temperature fluctuations are often caused by factors such as aging of heating elements, corrosion of thermocouple protection tubes leading to temperature measurement deviations, degradation of furnace insulation materials, and airflow disturbances. Experiments show that even temperature deviations within ±5% can lead to abnormal grain growth, decreased density, and a reduction in thermal conductivity of more than 30%. Local over- or under-burning can also cause substrate warping, surface cracks, and internal micropores, severely reducing batch production yield. Current sintering monitoring mainly relies on platinum-rhodium thermocouples and temperature sensing rings. Thermocouples only output single-point temperatures, making it difficult to characterize the temperature field differences in large-area loading areas. Temperature sensing rings measure temperature based on the shrinkage principle, but under the extreme high temperatures (>1800℃) and nitrogen-hydrogen atmospheres of aluminum nitride sintering, they are prone to softening and deformation. Their shrinkage characteristics are severely mismatched with the sintering shrinkage of the green blank after lamination and printing, and they may even melt and fail directly, failing to provide effective indications. Furthermore, temperature sensing rings only represent the thermal process at their own location and cannot directly reflect the sintering shrinkage behavior of the actual product blank. When furnace temperature drifts slowly, these methods are slow to respond and are often only discovered after batches of products have poor performance or ceramic defects, leading to serious economic losses and delivery risks. Summary of the Invention

[0005] The purpose of this invention is to provide a method for monitoring the sintering consistency of aluminum nitride ceramics, and to solve the following technical problems.

[0006] The objective of this invention can be achieved through the following technical solutions: A method for monitoring the sintering consistency of aluminum nitride ceramics includes the following steps: Step S1: Obtain green ceramic sheets of the same batch as the aluminum nitride ceramic to be sintered. Process a through hole on the green ceramic sheet according to a preset size. Obtain a metal paste of the same raw material as the aluminum nitride ceramic to be sintered with a preset mass. Fill the through hole with the metal paste and print a center circular mark of a preset diameter on the surface of the green ceramic sheet by screen printing. Then, perform isostatic pressing and cutting on the green ceramic sheet to obtain a standard sample green body. Step S2: Place several standard sample green blanks together with the aluminum nitride ceramic to be sintered into the sintering furnace, and complete the debinding and high-temperature sintering using the same process to obtain several sintered standard parts; Step S3: For any sintered standard part, obtain the diameter of the central circular mark on the sintered standard part, and record it as the diameter after sintering. Obtain the ratio of the diameter after sintering to the preset diameter to obtain the shrinkage rate of the sintered standard part. Based on the shrinkage rate of each sintered standard part, obtain the shrinkage rate fluctuation value, and determine the consistency of this batch of sintering based on the shrinkage rate fluctuation value.

[0007] As a further aspect of the present invention: the preset size is the diameter of the through hole, the diameter is set to be greater than the line width of the central circular mark, and the diameter of the through hole is smaller than the diameter of the central circular mark.

[0008] As a further aspect of the present invention: the process of setting the diameter of the central circular mark includes: Historical sintering data of several green ceramic pieces under historical sintering processes are obtained. The average shrinkage rate of the green ceramic pieces is obtained based on the historical sintering data. An enlarged design diameter is calculated based on the average shrinkage rate and used as the preset diameter of the central circular mark. The design diameter ensures that the actual diameter of the central circular mark formed on the sintered standard piece after sintering shrinkage falls within the optimal recognition range of the optical measuring equipment.

[0009] As a further aspect of the present invention: the process of printing on the surface of the green ceramic sheet by screen printing includes: A screen printing plate with a central circular mark pattern of a preset diameter is set up. Under the pressure of a scraper, the metal paste is transferred through the screen printing plate to the surface of the green ceramic sheet. After leveling, film formation and drying, a central circular mark is obtained on the surface of the green ceramic sheet.

[0010] As a further aspect of the present invention: the process of obtaining the shrinkage rate of the sintered standard part is as follows: S = r / R × 100%, where r is the diameter after sintering and R is the preset diameter.

[0011] As a further aspect of the present invention: the process of obtaining the shrinkage rate fluctuation value includes: Obtain the arrangement of each sintered standard part. Based on the arrangement, for any sintered standard part, obtain several sintered standard parts adjacent to the sintered standard part, and record these several sintered standard parts as adjacent sintered standard parts. Obtain the shrinkage rate of the sintered standard part and the shrinkage rate of all its adjacent sintered standard parts, obtain the standard deviation of the shrinkage rate, and record it as the standard deviation of the shrinkage rate of the sintered standard part. Obtain the standard deviation of the shrinkage rate of each sintered standard part, obtain the average value of each standard deviation of the shrinkage rate, and obtain the shrinkage rate fluctuation value.

[0012] As a further aspect of the present invention: the process of determining the consistency of this batch of sintering based on the shrinkage fluctuation value includes setting a consistency threshold; if the shrinkage fluctuation value is greater than the consistency threshold, it is determined that there is a temperature field abnormality in this batch of sintering.

[0013] As a further aspect of the present invention: the process of determining the consistency of this batch of sintering based on the shrinkage rate fluctuation value includes setting a consistency threshold; if the shrinkage rate fluctuation value is less than or equal to the consistency threshold, then it is determined that this batch of sintering is without abnormality.

[0014] The beneficial effects of this invention are: This method uses the same batch of green ceramic sheets and metal paste as the product to be sintered to prepare standard samples, and undergoes the same punching, filling, printing, stacking, cutting, and debinding sintering process. This fundamentally ensures that the standard parts are highly identical to the product in terms of material composition, layer density, thermal history, and shrinkage characteristics. The standard parts become a shrinkage substitute for the product, and their sintering shrinkage behavior can truly and directly reflect the actual densification process of the product blank at high temperature. This fundamentally overcomes the inherent defect of the temperature measuring ring softening, deforming, or even melting under extreme high temperature nitrogen atmosphere due to material heterogeneity, resulting in a complete mismatch between the shrinkage behavior and the product. This makes the monitoring results truly representative and instructive for the sintering quality of the product.

[0015] This method utilizes screen printing technology to pre-fabricate measurement patterns, including features such as a central circular mark, on the surface of standard green blanks. The shrinkage rate is calculated based on the dimensional changes of this pattern before and after sintering, transforming abstract furnace temperature fluctuations into intuitive, quantifiable, and traceable graphic dimensional data. The pattern is formed from a metal paste of the same material as the product, which can be stably retained after high-temperature sintering. Furthermore, the dimensions of the circular mark, such as line width and diameter, are optimized to form a high-contrast, foolproof optical measurement reference with the metal column below, significantly improving the accuracy, repeatability, and automated identification efficiency of shrinkage rate measurement.

[0016] This method also allows for the simultaneous acquisition of shrinkage rate distribution data across the entire effective working area by placing standard parts at multiple locations within the furnace, thereby calculating the temperature field uniformity fluctuation value. By statistically analyzing the average shrinkage rate of standard parts in consecutive batches, the batch-to-batch furnace temperature stability fluctuation value can be obtained. This method can sensitively capture early signals of temperature field imbalance and long-term process drift within the furnace, enabling operators to perform equipment calibration or process intervention in a timely manner before product performance deviates or ceramic defects occur. This effectively avoids batch-related quality accidents and economic losses. Furthermore, it does not require the introduction of additional heterogeneous temperature measuring materials or complex equipment modifications. The method is simple to operate, low in cost, and has good versatility and promising prospects for widespread application. Attached Figure Description

[0017] The invention will now be further described with reference to the accompanying drawings.

[0018] Figure 1 This is a schematic diagram of the steps of a method for monitoring the sintering consistency of aluminum nitride ceramics according to the present invention; Figure 2 This is a schematic diagram of the central circular mark in the monitoring method for the sintering consistency of aluminum nitride ceramics of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Please see Figure 1 As shown, this invention provides a method for monitoring the sintering consistency of aluminum nitride ceramics, comprising the following steps: Step S1: Obtain green ceramic sheets of the same batch as the aluminum nitride ceramic to be sintered. Process a through hole on the green ceramic sheet according to a preset size. Obtain a metal paste of the same raw material as the aluminum nitride ceramic to be sintered with a preset mass. Fill the through hole with the metal paste and print a center circular mark of a preset diameter on the surface of the green ceramic sheet by screen printing. Then, perform isostatic pressing and cutting on the green ceramic sheet to obtain a standard sample green body. The central circular mark is as follows Figure 2 As shown, Figure 2The circular area in the diagram is the central circular mark. The four right angles surrounding this circular area are metallization positioning elements of the same origin as the product to be sintered, i.e., through holes filled with metal slurry. Here, D represents the diameter of the central circular mark, X1 represents the distance between the two upper through holes, and X2 represents the distance between the two lower through holes. If X1 is not equal to X2 after sintering, it indicates a temperature difference in the horizontal temperature field inside the furnace. Y1 represents the vertical center distance between the two through holes on the left, and Y2 represents the vertical center distance between the two through holes on the right. If Y1 is not equal to Y2 after sintering, it indicates a temperature difference in the vertical temperature field inside the furnace. The temperature uniformity of the horizontal and vertical temperature fields inside the furnace is tested simultaneously by placing standard test pieces at different vertical and horizontal positions. In a preferred embodiment of the present invention, the preset size is the diameter of the through hole, the diameter is set to be greater than the line width of the central circular mark, and the diameter of the through hole is smaller than the diameter of the central circular mark; It should be noted that the line width of the central circular mark is the thickness of the lines that make up the circular pattern when the measurement pattern is printed on the surface of the raw ceramic tile using a screen printing process; the aperture of the through hole is set to ensure that the metal column formed by the metal paste filling the through hole after sintering is completely contained in size by the central circular mark covering it. In a preferred embodiment of the present invention, the process of setting the diameter of the central circular mark includes: Historical sintering data of several green ceramic pieces under historical sintering processes are obtained. The average shrinkage rate of the green ceramic pieces is obtained based on the historical sintering data. An enlarged design diameter is calculated based on the average shrinkage rate and used as the preset diameter of the central circular mark. The design diameter ensures that the actual diameter of the central circular mark formed on the sintered standard piece after sintering shrinkage falls within the optimal recognition range of the optical measuring equipment. In a preferred embodiment of the present invention, the process of printing on the surface of the green ceramic sheet by screen printing includes: A screen printing plate with a central circular mark pattern of a preset diameter is set up. Under the action of the squeegee pressure, the metal paste is transferred through the screen printing plate to the surface of the green ceramic sheet. After leveling, film formation and drying, a central circular mark is obtained on the surface of the green ceramic sheet. It should be noted that several green ceramic sheets that have completed through-hole filling and surface pattern printing are aligned and stacked according to the same stacking order and number of layers as the product to be sintered. Then, the stack is sealed in a flexible sleeve and vacuumed. It is then placed in the pressure chamber of an isostatic pressing device. Under preset temperature and pressure conditions, pressure is applied uniformly in all directions through a liquid medium, so that each layer of green ceramic sheets is tightly bonded into a dense and uniformly distributed stacked blank. The stacked blank is then cut into units with the same external dimensions as the product to be sintered using a dicing or cutting wheel method. During the cutting process, the central circular mark is kept intact and located within the preset measurement area on the surface of the cut unit. This process produces a standard sample green blank that can be directly sintered in the furnace. In actual production, raw ceramic sheets from the same batch may exhibit slight fluctuations in density and thickness. During through-hole machining, burrs on the hole walls, edge chipping, or diameter deviations are prone to occur. These defects can disrupt the structural uniformity of the raw ceramic sheets, leading to abnormal local shrinkage during subsequent slurry filling and sintering, thus affecting the representativeness of the standard samples. In such cases, it is necessary to first screen the raw ceramic sheets from the same batch for uniformity, removing sheets with excessive thickness and density. Through-hole machining should be performed using CNC precision machining technology, optimizing tool parameters and machining paths, and eliminating machining stress and edge defects through rounded corner treatment at the hole opening. This ensures the dimensional and positional accuracy of the through holes and the smoothness of the hole walls, avoiding irreversible damage to the raw ceramic sheet substrate. When filling with metal paste, issues such as incomplete filling, internal air bubbles or voids, or paste overflow contaminating the surface of the green ceramic sheet can easily occur. Furthermore, during the subsequent drying process, paste shrinkage can lead to depressions and cracks, resulting in inconsistencies in the metal composition and density of the standard green sample compared to the finished product, thus affecting the accuracy of sintering shrinkage rate measurements. To address this problem, a vacuum-assisted filling process can be employed. This process uses a negative pressure environment to eliminate air bubbles in the paste, ensuring full filling of the through-holes. Optimizing the paste viscosity and solid content allows for precise control of the filling amount to prevent overflow. A gradient drying process is used to gradually adjust temperature and humidity, reducing shrinkage stress during the drying process and preventing depressions and cracks. Simultaneously, excess paste on the surface of the green ceramic sheet is promptly cleaned to maintain a clean printing surface. During screen printing, uneven screen tension, unstable squeegee parameters, and insufficient flatness of the raw ceramic sheet surface can easily lead to diameter deviations, rough edges, uneven ink layer thickness, and even missing prints or misalignments in circular marks. Furthermore, if the compression deformation of subsequent isostatic pressing is not considered, the printed marks are prone to ellipticization and dimensional distortion after pressing, affecting the accuracy of diameter measurement after sintering. Therefore, high-tension precision screens are required, and screen tension and alignment accuracy must be calibrated regularly. Squeegee pressure, angle, and printing speed should be optimized to ensure the stability of the printing process. Pre-treatment of the raw ceramic sheet surface is necessary to improve the flatness of the printed surface. Based on the theoretical compression rate of the isostatic pressing process, the preset diameter of the printed marks should be calculated and designed, reserving a margin for compression deformation. Simultaneously, the ink layer thickness should be controlled to prevent ink layer deformation or detachment during pressing, ensuring that the marks maintain a regular circular outline and dimensional accuracy after pressing. Because the stacking process parameters of the standard sample green body and the product are inconsistent, or the molding methods are different, the density of the two after stacking is easily different; the printed marks are easily deformed by pressure during the stacking process; the green body may also delaminate and chip during cutting, which will destroy the uniformity of the green body structure and make it impossible to guarantee the homogeneity with the product; therefore, the stacking process of the standard sample green body must be completely synchronized with the product to be sintered, and the same molding tooling as the product should be used to ensure that the green body is subjected to uniform stress. Step S2: Place several standard sample green blanks together with the aluminum nitride ceramic to be sintered into the sintering furnace, and complete the debinding and high-temperature sintering using the same process to obtain several sintered standard parts; In a preferred embodiment of the present invention, the process of completing the debinding and high-temperature sintering using the same process includes: The standard sample green body and the product to be sintered are placed in the same batch of the sintering furnace using the same loading method. First, under a flowing nitrogen or nitrogen-hydrogen mixed atmosphere, the temperature is slowly heated to 500-800°C at a heating rate of 0.5-2°C / min and held for 2-6 hours. This allows the organic binder and plasticizer in the standard sample green body to fully decompose thermally and be discharged from the furnace through airflow, completing the debinding process. After debinding, the furnace temperature is further increased to a high-temperature sintering temperature of 1800-1950°C at a heating rate of 3-10°C / min in the same furnace and held at this temperature for 2-8 hours. During the holding process, flowing nitrogen is continuously introduced to maintain a reducing sintering atmosphere, so that the standard sample green body and the product complete densification sintering under the exact same thermal history, resulting in sintered standard parts and sintered products with the surface completely retaining the measured pattern. In practical applications, inconsistencies may arise between the standard sample and the product in terms of loading posture, support method, and loading density. Furthermore, improper placement of the standard sample may fail to cover temperature differences within the furnace, leading to deviations in heating conditions and airflow contact, thus affecting the representativeness of subsequent shrinkage rate data. Therefore, it is necessary to use loading fixtures and support methods identical to those used for the product to be sintered. The placement posture of the standard sample green billets, their contact method with the firing plate, and the spacing within the furnace should all be synchronized with the product to avoid deviations in sintering behavior due to differences in stress or heating surfaces. Simultaneously, based on the temperature distribution characteristics of the sintering furnace, the standard sample green billets should be evenly distributed in key monitoring temperature zones such as the furnace center, edges, and upper and lower layers. Sufficient standard samples should be placed in each temperature zone to ensure a comprehensive reflection of the actual sintering conditions at different locations within the furnace. During loading, the overall loading density of the standard sample and the product should be controlled to maintain consistency with the loading density of the mass production batch, avoiding localized density differences that could cause airflow turbulence and thermal distortion within the furnace. Furthermore, during the debinding process, the through-hole structure of the standard sample green body and the decomposition path of organic matter in the homologous metal slurry may differ from those of the product, easily leading to asynchronous debinding, organic matter residue, or cross-contamination of decomposition products, which in turn affects the consistency of subsequent sintering shrinkage. In contrast, a debinding process curve that is completely synchronized with the product must be adopted, including heating rate, holding temperature and time, atmosphere flow rate, and pressure control parameters, to ensure that the standard sample and the product undergo the same debinding thermal process. Thermogravimetric analysis should be used to clarify the decomposition temperature range of organic matter in the standard sample green body, and a targeted holding section should be set in the debinding process to ensure that the decomposition and discharge of organic matter in the standard sample are completed synchronously with the product. The airflow organization in the furnace should be optimized, and the airflow should be guided to be evenly distributed through tooling structure to avoid cross-interference between the exhaust paths of the standard sample and the product. Furthermore, during high-temperature sintering, temperature gradients, atmosphere fluctuations, and process parameter deviations within the furnace can all lead to asynchronous densification processes between the standard sample and the product. Additionally, standard parts are prone to adhesion and damage to surface markings, affecting subsequent measurement accuracy. Therefore, a high-temperature sintering process identical to that of the product to be sintered must be employed, including heating rate, maximum sintering temperature, holding time, cooling curve, and pressure control, to ensure complete synchronization of densification and grain growth processes between the standard sample and the product. To address the furnace temperature characteristics, multiple points of the standard sample are arranged to cover different temperature zones within the furnace, enabling comprehensive monitoring of the furnace temperature distribution. The same high-temperature sintering material as the product is used, and the support surface of the standard sample green blank is isolated to prevent interfacial reactions and adhesion at high temperatures, protecting the central circular marking on the surface of the standard part. During the sintering stage, closed-loop temperature field and atmosphere control are employed to correct furnace temperature deviations in real time, ensuring temperature uniformity at different locations within the furnace and stabilizing the furnace atmosphere composition to avoid differences in sintering shrinkage behavior caused by fluctuations in oxygen and nitrogen partial pressures. It is important to note that sudden temperature changes, impact damage, or differences in storage environment during the unloading process can easily lead to cracking, damage to surface markings, or changes in dimensional stability of standard parts, affecting the accuracy of subsequent shrinkage rate measurements. Therefore, the same cooling and unloading process as the product should be used after sintering to avoid thermal stress cracking caused by sudden temperature changes. When unloading, sintered standard parts should be individually marked with their loading location and furnace batch information to achieve full-process traceability. After unloading, the surface of the standard parts should be visually inspected, and samples with deformed markings, damage, or obvious defects should be rejected. Qualified standard parts should be stored in a constant temperature and dry environment to avoid slight dimensional changes caused by moisture absorption or ambient temperature fluctuations. Step S3: For any sintered standard part, obtain the diameter of the central circular mark on the sintered standard part, and record it as the diameter after sintering. Obtain the ratio of the diameter after sintering to the preset diameter to obtain the shrinkage rate of the sintered standard part. Based on the shrinkage rate of each sintered standard part, obtain the shrinkage rate fluctuation value, and determine the consistency of this batch of sintering based on the shrinkage rate fluctuation value. In a preferred embodiment of the present invention, the shrinkage rate of the sintered standard part is obtained as follows: S = r / R × 100%, where r is the diameter after sintering and R is the preset diameter. In a preferred embodiment of the present invention, the process of obtaining the shrinkage rate fluctuation value includes: The arrangement of each sintered standard part is obtained. According to the arrangement, for any sintered standard part, several sintered standard parts adjacent to the sintered standard part are obtained, and these several sintered standard parts are all recorded as adjacent sintered standard parts. The shrinkage rate of the sintered standard part and the shrinkage rate of all its adjacent sintered standard parts are obtained. The standard deviation of the shrinkage rate is obtained and recorded as the standard deviation of the shrinkage rate of the sintered standard part. The standard deviation of the shrinkage rate of each sintered standard part is obtained, and the average value of the standard deviation of the shrinkage rate is obtained to obtain the shrinkage rate fluctuation value. In a preferred embodiment of the present invention, the process of determining the consistency of the sintering batch based on the shrinkage fluctuation value includes setting a consistency threshold. If the shrinkage fluctuation value is greater than the consistency threshold, it is determined that there is a temperature field abnormality in the sintering batch; otherwise, it is determined that there is no abnormality in the sintering batch. It is important to note that in practical applications, sintered standard parts are prone to instability after being removed from the furnace due to changes in ambient temperature and humidity, surface residues, or minor warping. Additionally, the presence of sintered deposits or oxide spots on the marked surface can cause errors in subsequent diameter measurements. Therefore, a standardized sample pretreatment process is necessary: ​​after removal from the furnace, the standard parts should be placed in a constant temperature and humidity environment for a specified time to eliminate dimensional fluctuations caused by thermal expansion and contraction and moisture absorption; a gentle cleaning process should be used to remove surface sintered residues to avoid damaging the central circular mark; samples with excessive warping should be screened through flatness testing, and qualified samples should be leveled and fixed using specialized fixtures to ensure that the marked plane is perpendicular to the measurement optical path during measurement, eliminating measurement errors caused by angular deviations; simultaneously, all standard parts should undergo a preliminary visual inspection to remove invalid samples with blurred markings, damage, or obvious sintering defects.

[0021] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A method for monitoring the sintering consistency of aluminum nitride ceramics, characterized in that, Includes the following steps: Step S1: Obtain green ceramic sheets of the same batch as the aluminum nitride ceramic to be sintered. Process a through hole on the green ceramic sheet according to a preset size. Obtain a preset mass of metal paste of the same origin as the metal paste used for the aluminum nitride ceramic to be sintered. Fill the through hole with the metal paste. Print a center circular mark of a preset diameter on the surface of the green ceramic sheet by screen printing. Then, perform isostatic pressing and cutting on the green ceramic sheet to obtain a standard sample green body. Step S2: Place several standard sample green blanks together with the aluminum nitride ceramic to be sintered into the sintering furnace, and complete the debinding and high-temperature sintering using the same process to obtain several sintered standard parts; Step S3: For any sintered standard part, obtain the diameter of the central circular mark on the sintered standard part, and record it as the diameter after sintering. Obtain the ratio of the diameter after sintering to the preset diameter to obtain the shrinkage rate of the sintered standard part. Based on the shrinkage rate of each sintered standard part, obtain the shrinkage rate fluctuation value, and determine the consistency of this batch of sintering based on the shrinkage rate fluctuation value. In step S1, the preset size is the diameter of the through hole, which is set to be greater than the line width of the central circular mark, and the diameter of the through hole is smaller than the diameter of the central circular mark.

2. The method for monitoring the sintering consistency of aluminum nitride ceramics according to claim 1, characterized in that, In step S1, the process of setting the diameter of the central circular mark includes: Historical sintering data of several green ceramic pieces under historical sintering processes are obtained. The average shrinkage rate of the green ceramic pieces is obtained based on the historical sintering data. An enlarged design diameter is calculated based on the average shrinkage rate and used as the preset diameter of the central circular mark. The design diameter ensures that the actual diameter of the central circular mark formed on the sintered standard piece after sintering shrinkage falls within the optimal recognition range of the optical measuring equipment.

3. The method for monitoring the sintering consistency of aluminum nitride ceramics according to claim 1, characterized in that, In step S1, the process of printing on the surface of the green ceramic sheet by screen printing includes: A screen printing plate with a central circular mark pattern of a preset diameter is set up. Under the pressure of a scraper, the metal paste is transferred through the screen printing plate to the surface of the green ceramic sheet. After leveling, film formation and drying, a central circular mark is obtained on the surface of the green ceramic sheet.

4. The method for monitoring the sintering consistency of aluminum nitride ceramics according to claim 1, characterized in that, In step S3, the shrinkage rate of the sintered standard part is obtained as follows: S = r / R × 100%, where r is the diameter after sintering and R is the preset diameter.

5. The method for monitoring the sintering consistency of aluminum nitride ceramics according to claim 1, characterized in that, In step S3, the process of obtaining the shrinkage rate fluctuation value includes: Obtain the arrangement of each sintered standard part. Based on the arrangement, for any sintered standard part, obtain several sintered standard parts adjacent to the sintered standard part, and record these several sintered standard parts as adjacent sintered standard parts. Obtain the shrinkage rate of the sintered standard part and the shrinkage rate of all its adjacent sintered standard parts, obtain the standard deviation of the shrinkage rate, and record it as the standard deviation of the shrinkage rate of the sintered standard part. Obtain the standard deviation of the shrinkage rate of each sintered standard part, obtain the average value of each standard deviation of the shrinkage rate, and obtain the shrinkage rate fluctuation value.

6. The method for monitoring the sintering consistency of aluminum nitride ceramics according to claim 1, characterized in that, In step S3, the process of determining the consistency of this batch of sintering based on the shrinkage fluctuation value includes setting a consistency threshold. If the shrinkage fluctuation value is greater than the consistency threshold, it is determined that there is a temperature field abnormality in this batch of sintering.

7. The method for monitoring the sintering consistency of aluminum nitride ceramics according to claim 6, characterized in that, In step S3, the process of determining the consistency of this batch of sintering based on the shrinkage fluctuation value includes setting a consistency threshold. If the shrinkage fluctuation value is less than or equal to the consistency threshold, it is determined that there is no abnormality in this batch of sintering.

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