Fabrication method and sensor for measuring thermal conductivity in high-temperature co-fired furnaces

Abstract

This application relates to a method for fabricating a high-temperature co-fired thermal conductivity measurement sensor and the sensor itself, belonging to the field of sensor technology. This application utilizes an integrated co-fired structure of a metal thick-film pattern and a ceramic green body, enabling the metal thick-film pattern to form a continuous transition interface with the ceramic substrate during sintering. This results in high interfacial bonding strength, effectively mitigating failure problems such as interface delamination, warping, or cracking that easily occur under high-temperature or thermal cycling conditions, thereby improving the structural stability and service life of the sensor. Simultaneously, the co-fired structure effectively blocks the influence of external oxidizing or corrosive samples on the metal layer, making it suitable for complex or extreme testing environments. Since the co-firing process eliminates the bonding layer, this invention reduces the interfacial thermal resistance of Joule heat transfer to the sample during measurement, making the transient temperature rise response more closely match the theoretical heat transfer model, thereby improving the accuracy of thermal conductivity measurement.

Description

Technical Field

[0001] This application relates to the field of sensor technology, and in particular to a method for preparing a high-temperature co-fired thermal conductivity measurement sensor and the sensor itself. Background Technology

[0002] Transient Plane Source (TPS) thermal conductivity testing technology is a type of thermophysical property testing method that uses a planar metal heat source as the excitation unit and transient temperature rise response as the measurement basis. This method features short testing time, strong adaptability to sample morphology and size, and wide measurement range coverage, and can be applied to the thermal conductivity measurement of solids, powders, liquids, porous materials, and composite structures. In the research and development and thermal management of products such as power battery thermal management systems, servers and 5G communication equipment, high-power semiconductor devices, photovoltaic modules, high-temperature insulating bricks, and aerospace thermal protection structures, TPS has become one of the important means of thermal performance evaluation. The core component of common TPS thermal conductivity testing equipment is a planar metal spiral structure probe with dual functions of heating and temperature measurement, referred to as a TPS probe. This probe (meaning the same as a measurement sensor) typically consists of a metal layer with a double spiral structure and insulating encapsulation layers on both sides. The metal layer typically uses materials with stable resistance-temperature characteristics, such as nickel and platinum. The encapsulation layer uses appropriate electrical insulation materials depending on the application temperature; for example, polyimide film is commonly used at low temperatures, while mica sheets or alumina ceramic sheets are used at high temperatures. During testing, the probe undergoes Joule heating under constant power excitation, diffusing heat into the sample it contacts. The stronger the sample's thermal diffusivity, the faster the probe's temperature rises. By collecting the transient resistance changes of the metal layer and combining this with a heat transfer model, the thermal conductivity of the sample can be determined.

[0003] However, existing TPS probes generally employ a process of "preparing the metal layer first, then encapsulating it." This involves first fabricating a metal layer with a double-helix structure using processes such as etching and cutting, and then encapsulating the metal layer between two insulating layers using an adhesive layer. Probes prepared using this method can maintain relatively stable testing performance in room to medium-temperature applications, but are prone to significant performance degradation at high temperatures above 600 °C. The root cause lies in the fact that the metal layer and insulating layer are bonded by an adhesive, resulting in limited interfacial bonding strength. Furthermore, the significant difference in thermal expansion coefficients between the metal and the encapsulation materials such as ceramics / mica leads to stress concentration and crack propagation under high temperatures or repeated cycles, causing local delamination or even overall failure. Simultaneously, the presence of the adhesive layer introduces additional interfacial thermal resistance between the metal and insulating layers, slowing down the probe's transient thermal response and affecting the accuracy of the temperature rise curve and the reliability of thermal conductivity calculations.

[0004] For applications requiring higher temperatures, such as characterizing the thermal conductivity of ceramic materials, porous insulation materials, and molten salt systems above 1000 °C, traditionally packaged TPS probes are ill-suited to meet the requirements. The packaging interface is prone to thermal fatigue cracking and corrosion at high temperatures, often damaging the probe structure and causing functional loss. Therefore, designing a TPS probe fabrication process that can be integrally formed with the metal layer and ceramic substrate without a packaging interface and can withstand extreme temperature environments has become a pressing technical problem in this field. Summary of the Invention

[0005] Based on this, a method for fabricating a high-temperature co-fired thermal conductivity measurement sensor and the sensor itself are provided to solve the technical problems of insufficient interfacial bonding strength, high interfacial thermal resistance, and easy delamination of the encapsulation structure in existing transient planar heat source method measurement sensors under high-temperature conditions.

[0006] On the one hand, a method for fabricating a high-temperature co-fired thermal conductivity measurement sensor is provided, the method comprising: The first and second ceramic green bodies are prepared by tape casting or dry pressing. A thick metal film pattern is screen-printed on the upper surface of the first ceramic green body; The printed metal thick film pattern is leveled and dried, and the metal thick film pattern is initially cured to maintain morphological stability. The second ceramic green body is covered on the upper surface of the first ceramic green body with the metal thick film pattern, and the second ceramic green body and the first ceramic green body are tightly bonded to the metal thick film pattern by hot pressing, forming a ceramic-metal-ceramic laminated structure. The stacked structure is cut according to the predetermined sensor shape. The cut and shaped laminated structure is placed at a temperature of 1300-1800℃ for high-temperature co-firing to form a high-temperature co-firing thermal conductivity measuring sensor.

[0007] In one embodiment, the first ceramic green body and the second ceramic green body are alumina or aluminum nitride green bodies, and the thickness of the first ceramic green body and the second ceramic green body is 0.1 to 1 mm.

[0008] In one embodiment, the screen printing of a thick metal film pattern on the upper surface of the first ceramic green body includes: A temperature-measuring / heating metal thick film pattern is screen-printed on the upper surface of the first ceramic green body using a metal thick film paste.

[0009] In one embodiment, the metal thick film slurry comprises, by mass percentage: 60–85 wt% of a metallic phase, wherein the metallic phase is one of platinum, molybdenum or tungsten or an alloy thereof; 1-10 wt% of a high-temperature glass phase, wherein the high-temperature glass phase is one of aluminosilicate glass, rare earth silicate glass or high-silicon glass; 10–30 wt% organic phase.

[0010] In one embodiment, the screen printing of a temperature-sensing / heating metal thick film pattern on the upper surface of the first ceramic green body includes: The metal thick film pattern is a spiral, double spiral, serpentine, or zigzag structure with a linewidth of 0.1–2 mm and an outer diameter of 2–90 mm; the wet film thickness of the metal thick film is 5–100 μm.

[0011] In one embodiment, the process of leveling and drying the printed thick metal film pattern, and pre-curing the thick metal film pattern to maintain morphological stability, includes: The metal thick film pattern screen-printed on the upper surface of the first ceramic green body is placed in a horizontal position at room temperature and leveled for 15 to 90 minutes. The metal thick film pattern after convection leveling is dried by holding it at 80-120℃ for 20-60 minutes.

[0012] In one embodiment, the step of hot-pressing lamination to tightly bond the second ceramic green body and the first ceramic green body to the metal thick film pattern to form a ceramic-metal-ceramic laminate structure includes: Apply a pre-compression pressure of 3-10 MPa at 40-60℃ and maintain it for 2-5 minutes to allow the first ceramic green body, the second ceramic green body and the metal thick film pattern to initially adhere and remove air between the interfaces; The lamination temperature is raised to 60-80℃ and the pressure is increased to 10-20 MPa, and maintained for 3-10 minutes, so that the first ceramic green body and the second ceramic green body undergo uniform plastic deformation, and the metal thick film pattern is fully bonded to the first ceramic green body and the second ceramic green body; Apply a pressure of 15–30 MPa at 70–90℃ and maintain it for 3–10 min to complete the compaction and shaping of the laminated structure of the second ceramic green body, the metal thick film pattern and the first ceramic green body, and obtain a ceramic-metal-ceramic laminated structure.

[0013] In one embodiment, the contour cutting of the stacked structure according to a predetermined sensor shape includes: The cutting methods for contour trimming include one of the following: laser cutting, mechanical punching, diamond tool cutting, or CNC cutting.

[0014] In one embodiment, the step of subjecting the cut and shaped laminated structure to high-temperature co-firing at a temperature of 1300–1800°C includes: During high-temperature co-firing, the cut and shaped laminated structure is placed in the furnace cavity and heated to 400-600°C at a heating rate of 10-20°C / min, and held at that temperature for 15-45 min in an air atmosphere to remove the organic carrier. The furnace cavity is evacuated and a protective gas, including nitrogen and a hydrogen-nitrogen mixture, is introduced to form a stable protective atmosphere in the furnace cavity. The flow rate of the protective gas is controlled at 0.1 to 5 L / min. Under the protective atmosphere, the temperature is increased to the target sintering temperature of 1300-1800℃ at a heating rate of 3-10℃ / min and then held for 0.5-5 h.

[0015] On the other hand, a sensor is provided, which is fabricated according to the preparation method of the high-temperature co-fired thermal conductivity measurement sensor described above.

[0016] The aforementioned method for fabricating a high-temperature co-fired thermal conductivity measurement sensor and the sensor itself employ an integrated co-fired structure of a metal thick-film pattern and a ceramic green body. This allows the metal thick-film pattern to form a continuous transition interface with the ceramic substrate during sintering, resulting in high interfacial bonding strength. This effectively mitigates failure issues such as interface delamination, warping, or cracking that easily occur under high-temperature or thermal cycling conditions, thereby improving the sensor's structural stability and lifespan. Simultaneously, the co-fired structure effectively isolates the metal layer from the influence of external oxidizing or corrosive samples, making it suitable for complex or extreme testing environments. Since the co-firing process eliminates the bonding layer, this invention reduces the interfacial thermal resistance of Joule heat transfer to the sample during measurement, making the transient temperature rise response more closely match the theoretical heat transfer model, thus improving the accuracy of thermal conductivity measurement. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic flowchart illustrating the fabrication method of a high-temperature co-fired thermal conductivity measurement sensor in one embodiment of this application. Figure 2 This is a schematic diagram of the structure of a sensor fabricated using a high-temperature co-fired thermal conductivity measurement sensor according to one embodiment of this application. Figure 3 For the purpose of this application, a cross-sectional microstructure of the sensor is shown in one embodiment; Figure 4 This is a scanning electron microscope image of the overall cross-section of the sensor with the integrated co-fired structure of this application; Figure 5 A scanning electron microscope image of the overall cross-section of a sensor with an adhesive layer set for comparison. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0020] As described in the background section, existing transient planar heat source probes generally adopt a "first prepare a metal layer, then encapsulate" structure. This involves fabricating a double-helix metal layer, which is then encapsulated between two insulating materials using adhesives, glass phases, or other bonding layers. Its disadvantages are as follows: (1) Insufficient interfacial bonding strength and limited structural reliability The metal layer and the insulating layer are bonded together using organic adhesives or inorganic glass-phase adhesives. However, these adhesives gradually undergo pyrolysis or softening at high temperatures, significantly reducing the interfacial bonding strength. Simultaneously, at high temperatures, the difference in thermal expansion coefficients between the metal and the encapsulation layer leads to substantial thermal stress at the interface, making it prone to crack formation and propagation at the adhesive layer, ultimately resulting in localized delamination or overall failure.

[0021] (2) The interface thermal resistance is large, which affects the transient thermal response. Introducing an adhesive layer between the metal layer and the insulating layer lengthens the actual heat conduction path of the probe, increases the interfacial thermal resistance, and causes an additional delay in the transient temperature rise signal. For TPS measurement methods that rely on the inversion of thermal conductivity from the temperature rise curve, the interfacial thermal resistance directly affects the fitting accuracy of the heat transfer model, thereby reducing measurement accuracy.

[0022] (3) Difficult to resist corrosion The metal layer and the insulating layer are encapsulated by an adhesive layer. Micropores or cracks are easily formed at the interface between the metal layer and the insulating layer, making the probe susceptible to corrosion and erosion in molten salt, high-temperature oxidizing atmosphere or steam-containing environment, which in turn damages the metal layer.

[0023] To address the issues of insufficient interfacial bonding strength, high interfacial thermal resistance, and easy delamination of the encapsulation structure in existing TPS probes under high-temperature conditions, this invention creatively proposes a method for fabricating a high-temperature co-fired thermal conductivity measurement sensor. This method enables the metal thick film pattern and the ceramic substrate to be densified simultaneously during the sintering process and form an integrated structure, fundamentally eliminating the encapsulation interface and improving the sensor's structural stability, transient thermal response accuracy, and long-term reliability within the 1000–1600 ℃ range.

[0024] In one embodiment, such as Figure 2 As shown, a method for fabricating a high-temperature co-fired thermal conductivity measurement sensor is provided, comprising the following steps: Step S1: Prepare the first ceramic green body and the second ceramic green body by tape casting or dry pressing. Step S2: Screen print a thick metal film pattern on the upper surface of the first ceramic green body; Step S3: The printed metal thick film pattern is leveled and dried to pre-cure the metal thick film pattern and maintain its morphological stability. Step S4: The second ceramic green body is covered on the upper surface of the first ceramic green body with the metal thick film pattern, and the second ceramic green body and the first ceramic green body are tightly bonded to the metal thick film pattern by hot pressing, forming a ceramic-metal-ceramic laminated structure. Step S5: The stacked structure is cut according to the predetermined sensor shape. Step S6: The cut and shaped laminated structure is placed at a temperature of 1300-1800℃ for high-temperature co-firing to form a high-temperature co-firing thermal conductivity measuring sensor.

[0025] Specifically, an integrated co-firing structure of a thick-film metal pattern and a ceramic green body is adopted. This allows the thick-film metal pattern to form a continuous transition interface with the ceramic substrate during sintering, resulting in high interfacial bonding strength. This effectively improves failure problems such as interface delamination, warping, or cracking that easily occur under high temperature or thermal cycling conditions, thereby improving the structural stability and service life of the sensor. Simultaneously, the co-firing structure effectively blocks the influence of external oxidizing or corrosive samples on the metal layer, making it suitable for complex or extreme testing environments. Since the co-firing process eliminates the bonding layer, this invention reduces the interfacial thermal resistance of Joule heat transfer to the sample during measurement, making the transient temperature rise response more closely match the theoretical heat transfer model, thereby improving the accuracy of thermal conductivity measurement.

[0026] In this process, a first ceramic green body and a second ceramic green body are prepared by tape casting or dry pressing, respectively. A thick metal film pattern is then screen-printed on the upper surface of the first ceramic green body. The second ceramic green body is then bonded tightly to the first ceramic green body and the thick metal film pattern through hot pressing. Finally, a ceramic-metal-ceramic laminated structure is formed under high-temperature co-firing. This process not only ensures a tight bond between the thick metal film pattern and the ceramic substrate but also prevents delamination or warping of the metal layer and the ceramic substrate under high-temperature conditions, effectively improving the structural stability and long-term reliability of the sensor under extreme conditions.

[0027] In this embodiment, the first ceramic green body and the second ceramic green body are alumina or aluminum nitride green bodies, and the thickness of the first ceramic green body and the second ceramic green body is 0.1 to 1 mm.

[0028] Choosing alumina or aluminum nitride as the ceramic material allows for full utilization of their heat resistance, chemical stability, and high strength under high-temperature conditions, effectively preventing matrix material failure caused by high temperatures or corrosive media. Simultaneously, the appropriate thickness of the ceramic green body ensures that the structure provides good mechanical support after co-firing while also guaranteeing efficient heat conduction between the thick metal film and the substrate.

[0029] In this embodiment, the screen printing of a thick metal film pattern on the upper surface of the first ceramic green body includes: A temperature-measuring / heating metal thick film pattern is screen-printed on the upper surface of the first ceramic green body using a metal thick film paste.

[0030] In this process, a thick metal film pattern is screen-printed onto the upper surface of the first ceramic green body, using a thick metal film paste for printing the temperature sensing / heating element. This printing method effectively ensures that the metal film pattern is uniformly distributed on the ceramic substrate and achieves good adhesion to the ceramic through a co-firing process, resulting in high stability and reliability of the metal film in practical operation. The uniformity and stability of the thick metal film can improve the measurement accuracy of the sensor under high-temperature conditions, reduce temperature errors, and thus improve the sensor's response speed and accuracy.

[0031] In this embodiment, the metal thick film slurry comprises, by mass percentage: 60–85 wt% of a metallic phase, wherein the metallic phase is one of platinum, molybdenum or tungsten or an alloy thereof; 1-10 wt% of a high-temperature glass phase, wherein the high-temperature glass phase is one of aluminosilicate glass, rare earth silicate glass or high-silicon glass; 10–30 wt% organic phase.

[0032] This metal thick-film slurry formulation ensures the film-forming properties, adhesion, and conductivity of the metal thick-film pattern after sintering. The choice of metallic phases, such as platinum, molybdenum, or tungsten, provides high-temperature resistance, capable of withstanding thermal expansion during co-firing and the current conduction requirements under high-temperature conditions. The addition of a glassy phase improves the slurry's film-forming properties and post-sintering adhesion strength. The organic phase contributes to the modulation and uniform distribution of the slurry. This well-designed slurry formulation not only enhances the sensor's stability but also reduces the impact of thermal expansion mismatch on the bonding interface between the metal film and the ceramic substrate, thereby improving the sensor's long-term operational reliability.

[0033] In this embodiment, the screen printing of a temperature-measuring / heating metal thick film pattern on the upper surface of the first ceramic green body includes: The metal thick film pattern is a spiral, double spiral, serpentine, or zigzag structure with a linewidth of 0.1–2 mm and an outer diameter of 2–90 mm; the wet film thickness of the metal thick film is 5–100 μm.

[0034] The design of the metal thick film pattern employs spiral, double-spiral, serpentine, or zigzag structures. Through precise control of the linewidth and outer diameter, the metal thick film forms an approximately planar, geometrically symmetrical heat source distribution when electrically heated, thereby establishing a predictable transient thermal diffusion field in the sample under test. This pattern structure helps reduce the influence of boundary effects and parasitic heat flux on the measurement results, enabling the resistance change of the metal thick film to accurately reflect its overall average temperature rise process, thus improving the stability and reliability of the transient planar heat source method for thermophysical parameter inversion.

[0035] In this embodiment, the step of leveling and drying the printed metal thick film pattern to initially solidify the metal thick film pattern and maintain its morphological stability includes: The metal thick film pattern screen-printed on the upper surface of the first ceramic green body is placed in a horizontal position at room temperature and leveled for 15 to 90 minutes. The metal thick film pattern after convection leveling is dried by holding it at 80-120℃ for 20-60 minutes.

[0036] The printed thick-film metal pattern undergoes leveling and drying processes. Drying is carried out within a temperature range of 80–120℃ to promote solvent evaporation from the organic carrier and to initially solidify the thick-film metal pattern, thus maintaining dimensional stability and uniform film thickness before lamination and subsequent co-firing. The leveling and drying process reduces defects such as blistering, pinholes, or edge collapse caused by residual solvents, lowering the risk of thick-film migration or morphological distortion during subsequent lamination and ensuring a stable bonding interface between the thick-film metal pattern and the ceramic green body before co-firing. This contributes to obtaining consistent resistance-temperature response characteristics and improves the repeatability and long-term stability of the sensor output.

[0037] In this embodiment, the step of tightly bonding the second ceramic green body and the first ceramic green body with the metal thick film pattern through hot pressing lamination to form a ceramic-metal-ceramic laminate structure includes: Apply a pre-compression pressure of 3-10 MPa at 40-60℃ and maintain it for 2-5 minutes to allow the first ceramic green body, the second ceramic green body and the metal thick film pattern to initially adhere and remove air between the interfaces; The lamination temperature is raised to 60-80℃ and the pressure is increased to 10-20 MPa, and maintained for 3-10 minutes, so that the first ceramic green body and the second ceramic green body undergo uniform plastic deformation, and the metal thick film pattern is fully bonded to the first ceramic green body and the second ceramic green body; Apply a pressure of 15–30 MPa at 70–90℃ and maintain it for 3–10 min to complete the compaction and shaping of the laminated structure of the second ceramic green body, the metal thick film pattern and the first ceramic green body, and obtain a ceramic-metal-ceramic laminated structure.

[0038] That is, the conditions for the hot-press lamination method include: lamination temperature of 40-90 ℃, lamination pressure of 5-30 MPa, and lamination time of 5-20 min. The hot-press lamination process is carried out by a step-by-step pressurization method, including three stages: low-pressure pre-bonding, medium-pressure compaction, and high-pressure shaping.

[0039] In this process, hot-pressing lamination is used to achieve a good bond between the second ceramic green body, the first ceramic green body, and the thick metal film pattern. The hot-pressing conditions, such as a temperature of 40–90°C, a pressure of 5–30 MPa, and a lamination time of 5–20 min, ensure a tight bond between the thick metal film pattern and the ceramic substrate, avoiding voids or delamination between layers. This lamination process effectively improves the bonding strength and high-temperature resistance of the sintered ceramic-metal-ceramic laminate while maintaining the integrity of the metal pattern and the mechanical strength of the ceramic substrate, thereby increasing the reliability and service life of the sensor under extreme operating conditions.

[0040] In this embodiment, the step of contour cutting the stacked structure according to a predetermined sensor shape includes: The cutting methods for contour trimming include one of the following: laser cutting, mechanical punching, diamond tool cutting, or CNC cutting.

[0041] Among these methods, contour cutting of the laminated structure using laser cutting, mechanical punching, diamond tool cutting, or CNC cutting enables precise dimensional control and high-quality edge smoothness, ensuring the shape accuracy of the finished sensor. Precise cutting allows the sensor to achieve accurate positioning and stable performance during measurement, preventing instability caused by cutting errors and ensuring accurate measurement capabilities and long-term reliability under high-temperature conditions.

[0042] In this embodiment, the step of placing the cut and shaped laminated structure under high-temperature co-firing at a temperature of 1300–1800°C includes: During high-temperature co-firing, the cut and shaped laminated structure is placed in the furnace cavity and heated to 400-600°C at a heating rate of 10-20°C / min, and held at that temperature for 15-45 min in an air atmosphere to remove the organic carrier. The furnace cavity is evacuated and a protective gas, including nitrogen and a hydrogen-nitrogen mixture, is introduced to form a stable protective atmosphere in the furnace cavity. The flow rate of the protective gas is controlled at 0.1 to 5 L / min. Under the protective atmosphere, the temperature is increased to the target sintering temperature of 1300-1800℃ at a heating rate of 3-10℃ / min and then held for 0.5-5 h.

[0043] The process involves co-firing the cut and shaped layered structure at 1300–1800℃, controlling the holding time and sintering atmosphere (nitrogen, hydrogen-nitrogen mixture, air, or vacuum). This allows the thick metal film pattern to bond tightly with the ceramic substrate under solid-state conditions, forming a continuous, integrated sintered structure that optimizes the sensor's thermal and mechanical properties at high temperatures. Co-firing not only improves the bonding force between the metal and insulating layers but also effectively mitigates stress concentration caused by differences in thermal expansion between different materials under high-temperature and thermal cycling conditions by forming an integrated sintered structure. This enhances the sensor's structural stability, operational reliability, and long-term stability under high-temperature environments.

[0044] In the aforementioned method for fabricating a high-temperature co-fired thermal conductivity measurement sensor, an integrated co-fired structure of a metal thick-film pattern and a ceramic green body is employed. This allows the metal thick-film pattern to form a continuous transition interface with the ceramic substrate during sintering, resulting in high interfacial bonding strength. This effectively mitigates failure issues such as interface delamination, warping, or cracking that easily occur under high-temperature or thermal cycling conditions, thereby improving the sensor's structural stability and lifespan. Simultaneously, the co-fired structure effectively isolates the metal layer from the influence of external oxidizing or corrosive samples, making it suitable for complex or extreme testing environments. Since the co-firing process eliminates the bonding layer, this invention reduces the interfacial thermal resistance of Joule heat transfer to the sample during measurement, making the transient temperature rise response more closely match the theoretical heat transfer model, thus improving the accuracy of thermal conductivity measurement.

[0045] Example 1

[0046] Example 1 is a co-fired TPS probe with aluminum nitride ceramic as the upper and lower insulating layers and platinum thick film as the heating / temperature sensing metal layer. Its preparation method includes the following steps: (1) Aluminum nitride ceramic green body was prepared by tape casting method, the thickness of the green body was controlled to be 0.3 mm, and the obtained aluminum nitride green body was cut into rectangular pieces of 50 mm × 80 mm, which were used as the substrate for the upper and lower ceramic insulating layers. (2) Prepare a platinum thick film paste for screen printing, the paste being composed of the following raw materials by mass percentage: 75 wt% platinum powder; 10 wt% aluminosilicate glass powder as a high-temperature glass phase; and 15 wt% organic carrier, which is a mixture of polypropylene resin, terpineol and propylene glycol monomethyl ether acetate.

[0047] A cut aluminum nitride preform is used as the printing substrate, and a 325-mesh screen is used to print on its surface, such as... Figure 2 The platinum thick film pattern shown is a double helix structure with an outer diameter of 12 mm and a line width of 0.30 mm. The wet film thickness after printing is approximately 50 μm. Figure 2 In the process, a thick metal film pattern is printed on the lower aluminum nitride green layer 1. The cured thick metal film pattern 2 is placed between the lower aluminum nitride green layer 1 and the upper layer 3.

[0048] (3) After the printed metal thick film pattern has naturally leveled for 30 min, place it in a drying oven and dry it at 80 ℃ for 20 min.

[0049] (4) Place another cut aluminum nitride green blank onto the green blank printed with platinum film, so that the dried platinum film is located between the two green blanks. Place the laminated structure in a hot press laminating device for lamination. Set the lamination temperature to 90 ℃, the lamination pressure to 15 MPa, and the lamination time to 10 min. After lamination, the two aluminum nitride green blanks and the middle platinum film are fully bonded together to form an aluminum nitride-platinum-aluminum nitride laminated structure.

[0050] (5) The laminated structure is processed into the form shown by using laser cutting equipment. Figure 2 The outline shown gives it the required sensor shape.

[0051] (6) The preformed part after cutting is placed in a high-temperature sintering furnace and co-fired under a nitrogen atmosphere. The temperature is raised to 1400 ℃ and held for 3 h, and then cooled with the furnace to obtain a co-fired sensor with an integrated structure.

[0052] like Figure 3 The microstructure of the sensor cross-section shown indicates the presence of a continuous band-like structure in the center of the cross-section, with significantly higher brightness than the areas above and below. This band-like structure corresponds to the thick metal film layer formed during co-firing, with ceramic substrate layers on its upper and lower sides. The metal and ceramic layers achieved direct solid-state bonding during co-firing, resulting in tight interfacial contact, and no structural defects such as delamination or cracking were observed.

[0053] This cross-sectional feature demonstrates that the thick metal film in the TPS probe obtained by this invention can be stably embedded between the ceramic layers to form an integral metal-ceramic structure, thereby ensuring the structural integrity and interface reliability of the probe under high-temperature thermal conductivity testing conditions.

[0054] Example 2

[0055] Example 2 is a co-fired TPS probe with silicon nitride ceramic as the upper and lower insulating layers and tungsten thick film as the heating / temperature sensing metal layer. Its preparation method includes the following steps: (1) Silicon nitride ceramic green body was prepared by tape casting method. The thickness of the green body was controlled to be 0.20 mm. The prepared silicon nitride green body was cut into rectangular pieces of 50 mm × 80 mm and used as the substrate for the upper and lower ceramic insulating layers. (2) Prepare a tungsten thick film paste for screen printing. The paste is composed of the following raw materials by mass percentage: 70 wt% tungsten powder; 5 wt% high silica glass powder as a high temperature glass phase; and 25 wt% organic carrier, which is a mixture of butyl cellulose, terpineol and propylene glycol monomethyl ether acetate.

[0056] A cut aluminum nitride preform is used as the printing substrate, and a 400-mesh screen is used to print on its surface, such as... Figure 2 The tungsten thick film pattern shown. Figure 2In the process, a metal thick film pattern is printed on the lower aluminum nitride green blank, and an aluminum nitride green blank is placed on the metal thick film pattern. After curing, a thick film metal layer 3 is formed between the first ceramic 1 and the second ceramic 2.

[0057] (3) After the printed thick film has been naturally leveled for 30 min, it is placed in an oven and dried at 100 ℃ for 15 min.

[0058] (4) Take another aluminum nitride green body of the same size and cover it on the green body containing the tungsten thick film pattern, so that the tungsten thick film is located between the two ceramic green bodies. Place the laminate in a laminating equipment and perform hot pressing lamination under the following conditions: lamination temperature is 80 ℃, lamination pressure is 20 MPa, and lamination time is 15 min.

[0059] (5) Use a laser cutting machine to process the laminated structure to prepare a product such as Figure 2 The sensor's shape is shown.

[0060] (6) The cut preform was placed in a controlled atmosphere high-temperature sintering furnace and co-fired in a mixed atmosphere of 20% hydrogen and 80% nitrogen. The temperature was raised to 1700 °C and held for 2 h, and then cooled to room temperature with the furnace to obtain a co-fired sensor with an integrated structure.

[0061] In one embodiment, such as Figure 2 As shown, a sensor is provided, which is fabricated according to the preparation method of the high-temperature co-fired thermal conductivity measurement sensor described above.

[0062] like Figure 4 As shown, Figure 4 This is a scanning electron microscope image of the overall cross-section of the sensor integrally co-fired according to this application. It shows no adhesive layer, a continuous interface transition, and tight bonding. A thick-film metal layer 3 is formed between the first ceramic 1 and the second ceramic 2.

[0063] like Figure 5 As shown, Figure 5 A cross-sectional scanning electron microscope image of a sensor with an adhesive layer for comparison shows that, upon heating, a large gap is easily formed between the adhesive layer and the insulating layer (ceramic). The sensor with the adhesive layer includes, from bottom to top, a first ceramic insulating layer 4, an adhesive layer 5, a metal layer 6, and a second ceramic insulating layer 7, with a gap between the first ceramic insulating layer 4 and the adhesive layer 5.

[0064] By comparing the overall cross-sectional scanning electron microscope (SEM) images of the sensor integrally co-fired in this application with those of the sensor with a corresponding adhesive layer, it can be seen that the sensor in this application has a seamless structure and a tight connection.

[0065] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0066] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for fabricating a high-temperature co-fired thermal conductivity measuring sensor, characterized in that, The application relates to a high-temperature co-fired thermal conductivity coefficient measuring sensor. The application comprises the following steps: preparing a first ceramic green body and a second ceramic green body by flow casting or dry pressing; screen printing a metal thick film pattern on the upper surface of the first ceramic green body; performing leveling and drying treatment on the printed metal thick film pattern, and preliminarily solidifying the metal thick film pattern to keep the shape stable; covering the second ceramic green body on the upper surface of the first ceramic green body provided with the metal thick film pattern, and tightly combining the second ceramic green body and the first ceramic green body with the metal thick film pattern by hot pressing lamination to form a ceramic-metal-ceramic laminated structure; contour cutting the laminated structure according to a predetermined sensor shape; 2. The method of claim 1, wherein the high temperature co-fired thermal conductivity measurement sensor is prepared by the steps of: placing the contour-cut laminated structure into a high-temperature co-firing furnace at a temperature of 1300-1800 DEG C to form the high-temperature co-fired thermal conductivity coefficient measuring sensor.

3. The method of claim 1, wherein the high temperature co-fired thermal conductivity measurement sensor is prepared by the steps of: The first ceramic green body and the second ceramic green body are alumina or aluminum nitride green bodies, and the thickness of the first ceramic green body and the second ceramic green body is 0.1-1 mm. The step of screen printing the metal thick film pattern on the upper surface of the first ceramic green body comprises the following steps:

4. The method of claim 3, wherein the high temperature co-fired thermal conductivity measurement sensor is prepared by the steps of: screen printing a temperature measuring / heating metal thick film pattern on the upper surface of the first ceramic green body by using a metal thick film paste. The metal thick film paste comprises the following components in percentage by mass: 60-85 wt% of a metal phase, wherein the metal phase is one of platinum, molybdenum or tungsten or an alloy thereof; 1-10 wt% of a high-temperature glass phase, wherein the high-temperature glass phase is one of alumino-silicate glass, rare earth silicate glass or high-silica glass; 5. The method of claim 1, wherein the high temperature co-fired thermal conductivity measurement sensor is prepared by the steps of: 10-30 wt% of an organic phase. The step of screen printing the temperature measuring / heating metal thick film pattern on the upper surface of the first ceramic green body comprises the following steps:

6. The method of claim 1, wherein the high temperature co-fired thermal conductivity measurement sensor is prepared by the steps of: the metal thick film pattern is in a spiral, double spiral, serpentine or broken line structure, the line width is 0.1-2 mm, the outer diameter is 2-90 mm, and the wet film thickness of the metal thick film is 5-100 mu m. The step of performing leveling and drying treatment on the printed metal thick film pattern, and preliminarily solidifying the metal thick film pattern to keep the shape stable comprises the following steps: placing the metal thick film pattern screen printed on the upper surface of the first ceramic green body in a horizontal position at room temperature, and performing leveling treatment for 15-90 minutes; 7. The method of claim 1, wherein the high temperature co-fired thermal conductivity measurement sensor is prepared by the steps of: providing a substrate; depositing a first layer of a first material on the substrate; depositing a second layer of a second material on the first layer; and depositing a third layer of a third material on the second layer. performing drying treatment on the metal thick film pattern after the leveling treatment by keeping the drying condition at 80-120 DEG C for 20-60 minutes. The step of tightly combining the second ceramic green body and the first ceramic green body with the metal thick film pattern by hot pressing lamination to form a ceramic-metal-ceramic laminated structure comprises the following steps: applying a pre-pressing pressure of 3-10 MPa at 40-60 DEG C for 2-5 minutes to preliminarily combine the first ceramic green body, the second ceramic green body and the metal thick film pattern and remove air between the interfaces; increasing the lamination temperature to 60-80 DEG C and increasing the pressure to 10-20 MPa for 3-10 minutes to make the first ceramic green body and the second ceramic green body uniformly plastically deform, and make the metal thick film pattern fully combine with the first ceramic green body and the second ceramic green body; Apply a pressure of 15–30 MPa at 70–90℃ and maintain it for 3–10 min to complete the compaction and shaping of the laminated structure of the second ceramic green body, the metal thick film pattern and the first ceramic green body, and obtain a ceramic-metal-ceramic laminated structure.

8. The method of claim 1, wherein the high temperature co-fired thermal conductivity measurement sensor is prepared by, The step of contour cutting the stacked structure according to the predetermined sensor shape includes: The cutting methods for contour trimming include one of the following: laser cutting, mechanical punching, diamond tool cutting, or CNC cutting.

9. The method of claim 1, wherein the high temperature co-fired thermal conductivity measurement sensor is prepared by, The step of placing the cut and shaped laminated structure at a temperature of 1300-1800℃ for high-temperature co-firing includes: During high-temperature co-firing, the cut and shaped laminated structure is placed in the furnace cavity and heated to 400-600°C at a heating rate of 10-20°C / min, and held at that temperature for 15-45 min in an air atmosphere to remove the organic carrier. The furnace cavity is evacuated and a protective gas, including nitrogen and a hydrogen-nitrogen mixture, is introduced to form a stable protective atmosphere in the furnace cavity. The flow rate of the protective gas is controlled at 0.1 to 5 L / min. Under the protective atmosphere, the temperature is increased to the target sintering temperature of 1300-1800℃ at a heating rate of 3-10℃ / min and then held for 0.5-5 h.

10. A sensor, characterized by The sensor is manufactured using the method for preparing a high-temperature co-fired thermal conductivity measuring sensor according to any one of claims 1 to 9.

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