Multi-layer composite ceramic metal packaging method for high-temperature pressure sensor

Abstract

The invention relates to the technical field of integrated circuit manufacturing, and discloses a multilayer composite ceramic metal packaging method for a high-temperature pressure sensor, and the method comprises the steps: executing atmosphere chemical potential pinning operation when the temperature of a sintering furnace enters a maximum shrinkage rate temperature region of a metalized functional layer; the dew point is increased to a pinning set value by adjusting the wet-hydrogen ratio of the process gas, so that the oxygen partial pressure is in a metastable state interval of oxidation-reduction reaction balance; according to the method, by introducing a chemical potential control dimension independent of a thermal field and utilizing a metastable state oxygen adsorption micromechanism, excessive shrinkage of the refractory metal in a specific temperature zone is inhibited in a targeted mode, and therefore the thermal field of the refractory metal can be effectively controlled. Transient shear stress generated by dynamic mismatch of a heterogeneous interface is eliminated, and the air tightness and the mechanical stability of the packaging structure under the high-temperature working condition are improved.

Description

Technical Field

[0001] This invention relates to a multilayer composite ceramic-metal packaging method for high-temperature pressure sensors, belonging to the field of integrated circuit manufacturing technology. Background Technology

[0002] Currently, high-temperature co-fired ceramic technology, with its thermal stability, high mechanical strength, and airtightness, serves as a core packaging method for pressure sensors in extreme working conditions in aerospace and oil exploration. This technology involves stacking multiple layers of ceramic green tape with metallized slurry and co-firing them at high temperature in a single process, achieving integrated mechanical support and electrical interconnection. Traditional co-firing processes employ a single thermal field control logic, setting a fixed heating rate and holding time to drive the debinding and densification sintering of heterogeneous materials. Due to the difference in sintering activation energy characteristics between the tungsten-molybdenum refractory metal functional layer and the alumina oxide ceramic matrix, the metal phase has a lower surface diffusion barrier in a specific high-temperature range, maintaining a high shrinkage and creep rate even under isothermal or cooling conditions. The shrinkage rate of oxide ceramics lags behind. The difference in intrinsic material properties means that existing single thermal field control cannot maintain the ceramic sintering driving force while independently suppressing excessive shrinkage of the metal phase.

[0003] To avoid the challenges of matching heterogeneous materials, existing technologies often improve the macroscopic physical structure of devices or employ step-by-step assembly and welding processes to alleviate stress. For example, Chinese invention patent CN110057487B discloses an all-ceramic ultra-high temperature pressure sensor and its packaging method. This method achieves a leadless sealed connection between the pressure-sensitive component, the reading antenna, and the casing through ceramic welding, solving the problem of high-temperature oxidation failure of traditional leaded structures. Essentially, this method focuses on static structural assembly and physical packaging. It does not address the core kinetic mismatch problem in the co-firing process of heterogeneous materials. It cannot actively intervene in the significant shrinkage rate difference between the metal phase and the ceramic phase in real time during the critical temperature range of sintering densification. It lacks a dynamic control mechanism for key process parameters of sintering atmosphere chemical potential and makes it difficult to target and suppress the diffusion of refractory metal atoms on the surface using the oxygen adsorption effect at the microscopic level. This results in residual transient shear stress at the heterogeneous interface inside the package due to kinetic mismatch, limiting the long-term airtight reliability of the device under extreme thermal shock conditions.

[0004] Therefore, the technical problem to be solved by this invention is to break through the limitations of single thermal field control, construct an orthogonal control dimension for independently intervening in the sintering dynamics of specific material phases, and realize real-time synchronization of shrinkage rate and full-process stress management of heterogeneous materials. Summary of the Invention

[0005] To address the problems mentioned in the background art, the technical solution of the present invention is as follows: A multilayer composite ceramic-metal encapsulation method for high-temperature pressure sensors, comprising a stacking construction step, wherein a metallized functional layer is printed on a ceramic green tape layer according to a preset circuit layout and laminated to construct a composite green unit, and a rheological matching co-firing step is performed on the composite green unit, wherein the rheological matching co-firing step includes: When the sintering furnace temperature enters the maximum shrinkage rate temperature range of the metallized functional layer, an atmosphere chemical potential pinning operation is performed. By adjusting the volume flow ratio of hydrogen to water vapor in the process gas introduced into the sintering furnace, the furnace atmosphere dew point temperature is raised from the reduction set value to the pinning set value. The oxygen partial pressure in the furnace corresponding to the pinning set value is in the metastable range on the redox reaction equilibrium boundary of the metallized functional layer. The adsorbed oxygen atoms generated by the dissociation of water molecules in the atmosphere occupy the active sites on the grain surface of the metallized functional layer to suppress its surface diffusion, while keeping the metallized functional layer in a non-oxidized state. Maintain the pinning setting until the difference in instantaneous linear shrinkage between the metallized functional layer and the ceramic green tape layer converges to the preset synchronization threshold, and restore the atmosphere dew point temperature to the reduction setting.

[0006] Preferably, the reduction setting value is below -40 degrees Celsius, and the pinning setting value is between -10 degrees Celsius and +20 degrees Celsius; the operation of adjusting the volume flow ratio of hydrogen and water vapor in the process gas introduced into the sintering furnace includes introducing a wet hydrogen gas flow that has been wetted by a constant temperature water bath through a mass flow controller and mixing it with a dry hydrogen gas flow to establish a surface energy level control environment dominated by water vapor partial pressure in the maximum shrinkage rate temperature range.

[0007] Preferably, the rheology matching co-firing step further includes performing a differential discharge operation of organic matter during the low-temperature debinding stage. This operation, within a temperature range of 200 to 500 degrees Celsius, periodically adjusts the oxygen partial pressure in the furnace based on the time axis misalignment between the decomposition kinetics of the organic carrier in the metallized functional layer and the volatilization kinetics of the plasticizer in the ceramic green belt layer, thereby establishing a porous framework channel for the ceramic matrix before the metallized functional layer undergoes violent degassing.

[0008] Preferably, the rheological matching co-firing step further includes performing a reverse thermal expansion difference coupling cooling operation during the cooling phase, which reduces the instantaneous cooling rate during the cooling process. The function is defined as the inverse correlation function of the absolute value of the difference between the coefficients of thermal expansion of the ceramic green layer and the metallized functional layer at the current temperature T: ,in, Let be the instantaneous thermal expansion coefficient of the ceramic green ribbon layer at temperature T. Let T be the instantaneous thermal expansion coefficient of the metallized functional layer at temperature T, and K be a preset cooling efficiency constant. It is a non-zero numerical stability factor; in For temperature zones exceeding a preset difference threshold, the instantaneous cooling rate, determined by a function, is limited to below a preset safe rate.

[0009] Preferably, the maximum shrinkage rate temperature range is determined by a pre-sintering thermal analysis step, which includes: obtaining the thermal shrinkage differential curves of the metallized functional layer and the ceramic green tape layer in the current batch, identifying the characteristic temperature point in the thermal shrinkage differential curve where the first derivative of the shrinkage rate is zero, and mapping the characteristic temperature point to the trigger temperature of the initiation atmosphere chemical potential pinning operation in the rheological matching co-firing step.

[0010] Preferably, the metastable range is defined based on the oxidation thermodynamic data of the metal components in the metallized functional layer. The oxygen partial pressure corresponding to the pinning set value is between the equilibrium oxygen partial pressure for the metal components to form the lowest valence oxide and the reduction limit oxygen partial pressure for the metal components to maintain the metallic state, and a diffusion barrier film with a thickness of less than five atomic layers is formed at the grain boundary of the metallized functional layer.

[0011] Preferably, the metallized functional layer is selected from tungsten, molybdenum, or a tungsten-molybdenum alloy, and the ceramic green tape layer is selected from alumina or aluminum nitride; the preset synchronization threshold is set to a difference in linear shrinkage rate of 0.1 percent per minute; after the atmosphere chemical potential pinning operation is completed, the rheological matching co-firing step continues to raise the temperature to the highest densification temperature of 1,500 to 1,650 degrees Celsius.

[0012] Preferably, the reverse thermal expansion differential coupling cooling operation further includes locking the instantaneous cooling rate at a constant low rate when the furnace temperature passes through the plastic-brittle transition temperature range of the metallized functional layer, and maintaining this low rate until a transition layer with a chemical gradient is formed at the interface between the metallized functional layer and the ceramic green belt layer through atomic interdiffusion.

[0013] Preferably, the multilayer composite ceramic-metal package structure is a housing base with three-dimensional wiring capability. The metallized functional layer includes buried circuits formed between ceramic green tape layers and vertical interconnect vias penetrating the ceramic green tape layers. The atmospheric chemical potential pinning operation suppresses the planar shrinkage of the metallized functional layer while simultaneously suppressing the radial shrinkage of the metal filler in the vertical interconnect vias through the isotropic chemical potential.

[0014] Preferably, the rheological matching co-firing step adopts a compensation logic based on the specific surface area of ​​the raw materials. When the specific surface area of ​​the raw materials of the metallized functional layer increases, resulting in improved sintering activity, the dew point temperature of the pinning setting value is increased or the time for maintaining the pinning setting value is extended to compensate for the shrinkage rate deviation caused by the change in the activity of the raw materials.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. In high-temperature pressure sensors, a dimension independent of the chemical potential control of the thermal field atmosphere is constructed to solve the problem that relying solely on temperature regulation in integrated circuit packaging manufacturing cannot eliminate the kinetic mismatch of heterogeneous materials during sintering. The shrinkage rate of the metallized functional layer is higher than that of the high-activity temperature zone of the ceramic matrix. The wet hydrogen ratio of the process gas is adjusted to increase the dew point temperature. The adsorption and pinning effect of trace oxygen atoms on the surface of refractory metal particles is used to suppress the diffusion rate of metal atoms on the surface, thereby slowing down the densification process to match the ceramic matrix. Without changing the thermal field distribution and without affecting the normal sintering of oxide ceramics, the transient shear stress generated at the interface due to the difference in shrinkage rate is eliminated, ensuring the hermeticity and mechanical integrity of the multilayer composite packaging structure.

[0016] 2. Establish an orthogonal control system for temperature field and chemical potential field to reduce the consistency requirements of raw material batches in the manufacturing process. When facing batches of different specific surface areas or active metal slurries, there is no need to reconstruct complex sintering heating curves. Fine-tune the atmosphere dew point parameters in the chemical braking stage to compensate for fluctuations in the sintering driving force of the material. Based on the dynamic compensation logic of the intrinsic properties of the material, improve the high fault tolerance and adaptability of the process window, avoid production instability caused by frequent adjustments of thermal parameters, and improve the yield of packaging base manufacturing.

[0017] 3. By combining the reverse thermal expansion difference coupling cooling logic, a closed-loop stress management system is achieved for the entire process cycle from high-temperature sintering to cooling and unloading. During the heating and densification stage, the chemical braking of the atmosphere is used to synchronize the shrinkage rate and prevent the generation of sintering stress. During the cooling and annealing stage, the cooling rate is dynamically limited based on the change in the instantaneous thermal expansion coefficient difference between the metal and ceramic, providing stress relaxation time in the temperature range where the physical properties of the materials are severely mismatched. The chemical synchronization during the heating stage and the physical relaxation during the cooling stage work together to solve the microcrack defects in the entire process of high-temperature pressure sensor packaging and manufacturing, and ensure the long-term signal transmission stability of the device under subsequent high-temperature operating conditions. Attached Figure Description

[0018] Figure 1 This is a flowchart of the multilayer composite packaging process of the rheological matching co-firing technology of the present invention; Figure 2 This is a graph showing the thermal shrinkage rate and difference characteristic of the metallized functional layer and the ceramic green tape layer in this invention. Figure 3 This is a block diagram showing the hardware architecture and data interaction of the rheological matching co-firing closed-loop control system of the present invention. Detailed Implementation

[0019] The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Any modifications or substitutions made to the methods, steps, or conditions of the invention without departing from the spirit and substance of the invention shall fall within the scope of the invention.

[0020] This invention provides a multilayer composite ceramic-metal encapsulation method for high-temperature pressure sensors, including a stacking construction step, a rheological matching co-firing step, and a controlled cooling step. In the rheological matching co-firing step, a control procedure based on atmospheric chemical potential is established to address the interfacial stress problem caused by the asynchronous densification kinetics between the metallized functional layer and the ceramic green layer. This control procedure identifies a characteristic temperature point where the first derivative of the shrinkage rate of the metallized functional layer is zero, based on pre-acquired thermal shrinkage differential curves of the metallized functional layer and the ceramic green layer, and defines a temperature range where the shrinkage rate of the metal phase is higher than the maximum shrinkage rate of the ceramic phase. This temperature range is typically located in... to During this period, when the thermocouple monitoring reading inside the sintering furnace enters the temperature range of the maximum shrinkage rate, the central control unit sends a command to the gas mass flow controller in the gas pipeline to perform an atmosphere chemical potential pinning operation. This adjusts the volumetric flow ratio of hydrogen to water vapor in the process gas introduced into the furnace, thereby lowering the dew point temperature of the furnace atmosphere from the conventional reduction setpoint. The following instantaneous increase to the pinning setting value is located at... to During this period, a specific oxygen partial pressure environment is established inside the furnace. This oxygen partial pressure is in the metastable range on the redox reaction equilibrium boundary of tungsten or molybdenum. Adsorbed oxygen atoms generated by the dissociation of water molecules in the atmosphere occupy the active sites on the surface of the metallized functional layer grains, reducing the surface diffusion coefficient of metal atoms without oxidizing the metal body. The chemical barrier is used to suppress the planar shrinkage of the metallized functional layer and the radial shrinkage of the metal filler in the vertical interconnecting vias. This pinning setting is maintained until the difference in instantaneous linear shrinkage rate between the metallized functional layer and the ceramic green ribbon layer converges to a preset synchronization threshold, such as less than 0.1% per minute. The control unit drives the gas mass flow controller to cut off the high-humidity gas path, quickly restoring the atmosphere dew point temperature to the reduction setting value, removing the chemical pinning effect to allow the metal layer to continue densification sintering.

[0021] During the cooling stage after high-temperature sintering, a reverse thermal expansion difference coupled cooling operation is performed. Instead of a constant linear cooling rate, a dynamic cooling trajectory based on the intrinsic properties of the material is established. The control system pre-stores the thermal expansion coefficient difference curves of the ceramic green layer and the metallized functional layer as a function of temperature, and records the instantaneous cooling rate during the cooling process. Set as the inverse correlation function of the absolute value of the difference, that is, follow the relationship. ,in, Let T be the instantaneous thermal expansion coefficient of the ceramic at temperature T. Let T be the instantaneous thermal expansion coefficient of the metal at temperature T, and K be a preset cooling efficiency constant. As a non-zero numerical stability factor, based on this functional relationship, when the furnace temperature passes through a temperature range where the absolute value of the difference between the thermal expansion coefficients exceeds a preset difference threshold—for example, in the range where the metal undergoes a magnetic transformation or the ceramic glass phase solidifies—the control system limits the instantaneous cooling rate to below the stress relaxation critical rate, for example, less than... This allows time for interfacial atomic rearrangement and stress dissipation. In temperature zones with small differences in thermal expansion coefficients, cooling is automatically accelerated to improve production efficiency. When the furnace temperature passes through the plastic-brittle transition temperature range of the metallized functional layer, the operation locks the cooling rate at a constant low speed, inducing the formation of a transition layer with a chemical gradient at the metal-ceramic interface through atomic interdiffusion.

[0022] The rheological matching co-firing step also includes a differential discharge operation of organic matter during the low-temperature debinding stage. This addresses the time axis misalignment issue between the organic carrier in the metal slurry and the plasticizer volatilization kinetics in the ceramic green belt. to Within the specified temperature range, the oxygen partial pressure inside the furnace is periodically adjusted. By alternately introducing oxidizing and weakly reducing atmospheres, the decomposition rates of different organic components are differentially controlled. Before the metallized functional layer undergoes violent venting, a porous framework channel is formed in the ceramic matrix to prevent gas accumulation and microscopic delamination defects. The atmosphere chemical potential pinning start-up temperature is determined by using a thermal expansion meter to measure the peak temperature corresponding to the first derivative of the shrinkage rate of the metallized functional layer. At this temperature, a dew point gradient test is performed. The furnace atmosphere dew point is gradually increased in two-degree Celsius increments. The sheet resistance of the metal layer is used to maintain the metal's conductivity range, and the difference in instantaneous shrinkage rates between the metal and ceramic layers converges to zero percent per minute. The minimum dew point temperature below 0.5°C is used as the pinning setpoint. Under the premise of not oxidizing the metal body, the minimum water vapor partial pressure boundary required to block grain boundary diffusion by surface adsorbed oxygen atoms is established. The constant K of the reverse thermal expansion difference coupled cooling function is determined based on the measured data of interface residual stress. Standard test samples with different K values ​​are prepared and the distribution of interface residual stress field after cooling is determined by micro Raman spectroscopy. The K value is selected as the production control parameter when the maximum tensile stress at the interface is less than 80% of the fracture toughness of the ceramic matrix. This parameter limits the instantaneous cooling rate curve so that the thermal stress accumulation rate of the material in the temperature zone of abrupt change in the thermal expansion coefficient difference is lower than the interface atomic stress relaxation rate.

[0023] Example 1: This example demonstrates the specific operation of a high-performance aero-engine pressure sensor packaging manufacturing scenario. In the high-temperature sensor packaging manufacturing scenario for monitoring aero-engine combustion chamber pressure, the packaging base used needs to maintain airtightness and electrical connection stability for a long period at a high temperature of 600 degrees Celsius. This condition poses a challenge to the bonding strength of heterogeneous material interfaces, approaching physical limits. Traditional co-firing processes of alumina ceramics and tungsten metal often experience airtightness failure in the early stages of service due to residual micro-stress from the manufacturing process under such extreme thermal cycling conditions. To address this manufacturing challenge, this example employs the aforementioned rheological matching co-firing method to process a composite green body unit formed by stacking 96% alumina ceramic green strip and high-purity tungsten metal slurry. During the sintering process, when entering the high-activity temperature range of 1150 to 1300 degrees Celsius, the surface diffusion rate of tungsten metal particles excited by heat is higher than the rearrangement rate of alumina grains. If conventional methods are maintained... In the original atmosphere, the asynchronous shrinkage rates of the two will lead to cumulative shear stress at the interface. At this time, the control system performs an atmosphere chemical potential pinning operation according to a preset program, driving the gas flow control unit to change the mixing ratio of hydrogen and water vapor, and instantly raising the dew point temperature of the atmosphere in the furnace from -45 degrees Celsius to 10 degrees Celsius. Under this dew point environment, the oxygen partial pressure established in the atmosphere is in the redox metastable equilibrium range of tungsten metal. The oxygen atoms dissociated from water molecules are adsorbed on the surface of tungsten particles and grain boundaries, forming a nanoscale chemical barrier. This barrier does not generate a macroscopic oxide phase, but reduces the surface diffusion coefficient of tungsten atoms by occupying surface active sites, forcing the shrinkage rate of the tungsten metal layer to decrease and keep it synchronized with the alumina ceramic matrix that has not yet drastically shrunk. This mechanism of using chemical equilibrium shift to compensate for physical thermodynamic differences in real time eliminates the transient stress source caused by shrinkage mismatch at the heterogeneous interface without changing the sintering temperature curve.

[0024] After densification sintering and entering the cooling stage, due to the non-linear difference in the thermal expansion coefficients of tungsten and alumina with temperature, an expansion mismatch peak will appear in a specific temperature range. This embodiment does not employ the traditional linear cooling method, but instead performs a reverse thermal expansion difference coupled cooling operation. The control system retrieves the stored material thermal expansion coefficient difference curves in real time, and based on... The instantaneous cooling rate is calculated using a relational formula. When the furnace temperature passes through the brittle transition range with drastic differences in physical properties, the system automatically reduces the cooling rate to 0.5 degrees Celsius per minute. Within this low-speed cooling window, atoms on both sides of the interface have sufficient time for thermal motion and interdiffusion, forming a transition layer with a chemical composition gradient. This transition layer acts as a stress buffer zone during subsequent rapid cooling and service thermal shock. The final packaged base was tested by a helium mass spectrometer leak detector, and the leakage rate was less than 10 to the power of -9 Pascal cubic meters per second. After undergoing 500 thermal shock cycles from 0 to 600 degrees Celsius, no microcracks observable by scanning electron microscopy appeared on the interface.

[0025] Example 2: This example aims to construct a comparative test system based on real working conditions. The test platform uses an industrial-grade high-temperature vacuum sintering furnace, equipped with a high-precision dew point control module and a multi-channel temperature recorder to simulate the thermal field and atmosphere environment of batch manufacturing in actual production. The data acquisition system includes a scanning electron microscope (SEM) for microstructure characterization and a helium mass spectrometer leak detector for airtightness testing. All tests are performed in accordance with the GB / T2423.22-2012 environmental testing standard. The test design addresses the kinetic mismatch between the tungsten metallization layer and the alumina ceramic substrate during co-firing. An experimental matrix is ​​constructed that includes the sample group of this invention and two key control groups. All sample groups are prepared using the same batch of 96% alumina green tape and tungsten slurry. The only variable is the atmosphere control strategy and cooling rate control during the sintering process.

[0026] Control group A (traditional process): using a single reducing atmosphere, maintaining a dew point below -40 throughout the process. And during the cooling phase, 5 A linear cooling rate of / min was used to simulate the existing standard process. Control group B (thermal field control only): an isothermal hysteresis plateau was introduced in the high-temperature section to attempt to mitigate the shrinkage difference, but the atmosphere dew point was maintained at -40. As before, linear cooling is also used during the cooling stage. The sample group of this invention is at 1150°C. Up to 1300 The atmospheric chemical potential pinning operation was performed in the interval to raise the dew point to +10. During the cooling phase, reverse thermal expansion differential coupling cooling was performed. After the experiment started, the dimensional change rate of each sample group was monitored in real time throughout the sintering process using an in-situ thermal expansion meter. The data showed that upon entering 1150°C... At the critical temperature range, the shrinkage rate of the tungsten layer in control sample A increased sharply, and the difference between the shrinkage rate of the control sample A and the ceramic matrix rapidly widened to over 0.25% / min, indicating that the metal underwent independent shrinkage. Although control sample B had an isothermal plateau, the creep rate of the tungsten layer did not decrease significantly, and the difference remained at around 0.18% / min. In contrast, the sample of this invention showed significant shrinkage even when the dew point was increased to +10°C. At that instant, the shrinkage rate of the tungsten layer showed a step-like decrease, and the difference with the ceramic matrix was converged to within 0.05% / min. Table 1 lists the key process data of this stage in detail.

[0027] Table 1: Quantitative Comparison of Shrinkage Matching Degree of Heterogeneous Materials under Different Processing Conditions

[0028] Data interpretation shows that the sample group of this invention, by introducing a chemical potential pinning mechanism, utilizes adsorbed oxygen atoms to suppress the surface diffusion of tungsten atoms at the microscale, thereby modifying the kinetic behavior of the metallic phase and actively adapting to the shrinkage rhythm of the ceramic phase. Further microstructural analysis confirms that the sample group of this invention forms an interdiffusion transition layer with a thickness of approximately 2 micrometers at the interface, and no continuous pores or microcracks were observed, while the control group showed obvious interface delamination or microcrack networks. The final airtightness test results show that the average helium leakage rate of the sample group of this invention is [missing information]. Superior to control group A Compared with control group B This confirms that orthogonal control of chemical potential and thermal field can eliminate heterogeneous interface stress and improve the reliability and yield of high-temperature packaging structures.

[0029] Example 3: This example combines Figures 1 to 3 The method for multilayer composite ceramic-metal packaging for high-temperature pressure sensors is described, such as... Figure 1 As shown, the process begins with the stack-up construction steps, encompassing the metallization functional layer printing and green tape lamination operations to construct composite green units, followed by the differential discharge operation of organic materials. This operation takes place in 200... Up to 500 Within the specified range, a porous framework channel for the ceramic matrix is ​​established by periodically adjusting the oxygen partial pressure. In the core rheological matching co-firing stage, the system receives parameter mappings from the pre-sintering thermal analysis step. This analysis determines the pinning trigger temperature by identifying the temperature range of maximum shrinkage rate. Simultaneously, it performs atmospheric chemical potential pinning, raising the dew point to the pinning setpoint by adjusting the wet hydrogen ratio and using adsorbed oxygen atoms to suppress diffusion on the metal surface, thus entering the densification sintering stage. After the shrinkage rate difference converges, the reducing atmosphere is restored and the temperature is raised to 1500°C. up to 1650 At the highest densification temperature, after entering the cooling process, the system intervenes in the plastic-brittle transition temperature range, locking the instantaneous cooling rate at a constant low rate to induce interatomic interdiffusion at the interface. Simultaneously, it performs reverse thermal expansion difference coupling cooling, based on the logic that the cooling rate is inversely proportional to the absolute value of the difference in thermal expansion coefficients. Through dynamic control, a multi-layer composite ceramic-metal encapsulation structure with a shell and base was finally prepared, which met the airtightness requirements, had no heterogeneous interface shear stress, and had three-dimensional wiring capabilities.

[0030] like Figure 2As shown, the horizontal axis represents temperature, and the vertical axis represents shrinkage rate (%) / min. The solid line in the graph depicts the trajectory of the shrinkage rate of the metallized functional layer as a function of temperature, showing that it reaches a peak near 1200°C. The dashed line depicts the hysteretic change in the shrinkage rate of the ceramic green tape layer, while the dotted line clearly indicates the difference in shrinkage rates between the two. This graph visually reveals that, under uninterrupted conditions, the shrinkage rate of the metallized functional layer is higher than that of the ceramic matrix in a specific high-temperature range, and the difference in shrinkage rates is significant at 1150°C. Up to 1250 The range shows an increasing trend; for example... Figure 3 As shown, the system's hardware architecture is centered around a central control workstation, which integrates an atmosphere chemical potential pinning control module, a reverse thermal expansion difference coupling cooling module, a data acquisition and command distributor, and a material thermodynamics database. The workstation connects to the atmosphere control subsystem on the left by sending wet hydrogen ratio adjustment commands. This subsystem includes a gas mass flow controller group and a constant temperature water bath wetting device, which is responsible for injecting process gas into the high-temperature vacuum sintering furnace terminal. The workstation also sends temperature zone power commands to the sintering furnace terminal located in the middle, driving the multi-zone heating actuator to heat treat the composite green body unit. The in-situ real-time monitoring terminal on the right includes an in-situ thermal expansion meter, a high-precision dew point meter, and a calibration thermocouple array. It acquires the furnace state through in-situ probe coupling and transmits the generated real-time feedback data stream back to the central control workstation, forming a closed-loop control loop.

[0031] Example 4: This example aims to provide an in-depth technical analysis and process specification supplement to address the complex interfacial reaction mechanisms that may occur during the co-firing of the metallized functional layer (tungsten / molybdenum) and the ceramic green ribbon layer (alumina), and to explore how to precisely control this process to prevent the formation of harmful intermediate phases. Although the aforementioned examples have disclosed a macroscopic strategy of using atmospheric chemical potential pinning to suppress metal shrinkage, a more refined control model based on thermodynamic and kinetic coupling is still needed at the atomic-scale interfacial reaction control level to ensure that while suppressing metal diffusion, brittle oxide phases are not induced. or The generation of these components forms the microscopic basis for ensuring the long-term reliability of the packaging structure. In high-temperature sensor packaging applications involving high-frequency signal transmission, any tiny change in dielectric constant or inclusion of conductive oxides at the interface can cause signal attenuation or crosstalk at high frequencies. To address this, this embodiment constructs a standardized calibration procedure for accurately defining the safe chemical potential window. Based on the Gibbs free energy data of tungsten and alumina at different temperatures, a multidimensional phase diagram is drawn to clearly define the thermodynamically stable region where tungsten remains in its elemental state, alumina remains chemically inert, and no solid-phase reaction occurs between the two. Through a set of gradient experiments, the quantitative relationship between the partial pressure of water vapor in the atmosphere, characterized by the dew point, the growth rate of interface oxides, and the oxygen adsorption coverage on the metal surface is accurately determined at a specific temperature.

[0032] Specifically, the calibration procedure involves preparing a series of miniature test samples, placing them in a precision-controlled atmosphere furnace, and setting a constant temperature of 1250°C. and with 2 For gradient, in to The atmosphere dew point was gradually adjusted within a certain range. After maintaining the dew point for a specific time at each dew point, the sample was removed for X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM) analysis. The analysis focused on detecting the thickness of the oxygen adsorbed layer on the surface of the tungsten particles and the presence of oxygen at the interface. Bonding characteristics, experimental data show that when the dew point is lower than At this time, the oxygen adsorption layer coverage is insufficient, which cannot effectively inhibit the diffusion of tungsten atoms, resulting in a still high shrinkage rate of the metal layer; when the dew point is higher than At that time, obvious differences appeared in the XPS spectrum. The peak indicates that macroscopic oxides have begun to form on the surface of the tungsten particles. This will severely impair the conductivity and bonding strength of the interface, while to Within the dew point range, only a single-atom layer of chemically adsorbed oxygen was observed on the tungsten surface, and no brittle intermediate phase was detected at the interface. At this time, the shrinkage rate of the metal layer was effectively suppressed, and the interface was tightly bonded. Based on the above calibration results, this embodiment establishes a dynamic safety chemical potential window control logic: During the sintering process, the control system queries the pre-constructed phase diagram database according to the real-time furnace temperature, calculates the maximum allowable water vapor partial pressure at the current temperature, and sets a safety margin factor such as 0.8. The control system drives the gas mass flow controller to adjust the wet hydrogen ratio in real time to ensure that the actual atmosphere dew point is always below the dynamic safety upper limit, but above the minimum threshold required to suppress shrinkage. This dynamic control strategy based on the microscopic reaction mechanism not only achieves macroscopic shrinkage matching, but also eliminates the generation of harmful phases at the atomic scale, ensuring the excellent electrical performance and mechanical reliability of the packaging structure under high temperature and high frequency conditions.

[0033] Example 5: This example aims to address the issues of process parameter deviations and product performance instability caused by batch-to-batch fluctuations in raw material properties in large-scale industrial production scenarios. It constructs a pre-engineering procedure based on real-time on-site calibration and adaptive parameter calibration. This procedure is designed as an independent calibration module before the formal execution of the rheological matching co-firing step, ensuring that for each batch of new raw materials, the system can dynamically generate an optimal set of safe chemical potential windows and cooling trajectory parameters. Before the start of a typical production cycle, rapid thermodynamic fingerprint extraction of the raw materials is performed. Micro-standard samples are prepared from the current batch of ceramic green tape and metal slurry. A high-throughput thermal dilatometer is used for rapid temperature scanning to obtain real-time shrinkage differential curves. The system automatically identifies the actual maximum shrinkage rate temperature range and shrinkage initiation point of the current batch of material. Based on a preset kinetic deviation compensation algorithm, the temperature drift value and shrinkage rate difference relative to the baseline process are calculated.

[0034] If the calculated deviation exceeds the preset process tolerance threshold, such as... or Then, the chemical potential-thermal field joint calibration procedure is initiated. A set of orthogonal gradient sintering experiments is performed in a small-scale furnace, using dew point temperature and holding time as variables, to rapidly determine how well the metal / ceramic shrinkage difference can be suppressed within a safe range under the current raw material characteristics. The minimum dew point increase and the shortest heat preservation time were determined. Finally, this set of optimized parameters (including the corrected atmosphere dew point setpoint, switching time point, and K value in the cooling rate function) was used as a temporary process formula and automatically injected into the central control unit to guide the large-scale production of this batch of products. Through this closed-loop procedure of measurement-calibration-execution, it is ensured that even if the physical properties of raw materials fluctuate, the process system can still output consistent and high-quality packaged products.

[0035] Example 6: This example aims to address practical engineering problems encountered in large-scale industrial production, such as fluctuations in the microscopic properties of raw materials and drift in the thermal environment. It constructs a standardized process that includes adaptive property calibration and dynamic thermal compensation to ensure stable achievement of the core technical effects of this invention under complex operating conditions. To address potential differences in sintering activity between batches of raw materials, a pre-sintering kinetic fingerprint extraction procedure is established. Before each batch of new metallization slurry or ceramic green tape is put into production, a small sample is taken to prepare a standard test piece. This piece is then rapidly heated and scanned in a small thermal expansion apparatus simulating the actual sintering atmosphere. The first derivative of the linear shrinkage rate of the sample with respect to temperature, i.e., the shrinkage rate curve, is recorded and calculated in real time. The system automatically extracts the shrinkage initiation temperature from this curve. Temperature with maximum shrinkage rate If the actual measurement Deviation from the baseline process setting value exceeds Based on the preset temperature-kinetic compensation function, the trigger temperature point of the atmosphere chemical potential pinning operation in the main sintering process is automatically corrected to ensure that the dew point switching action is always precisely synchronized with the moment when the metal phase shrinks most violently.

[0036] To address potential issues such as uneven thermal field distribution or temperature sensor drift within high-temperature sintering furnaces, an in-situ thermal field calibration and feedback procedure is implemented. A calibrated thermocouple array is deployed in the critical temperature zones of the sintering furnace to periodically map the actual three-dimensional temperature distribution within the furnace chamber. The control system compares the actual temperature field with the set temperature field, calculating the temperature deviation coefficient for each heating zone. During atmosphere chemical potential pinning operations, the system not only adjusts the dew point based on the nominal temperature but also incorporates this deviation coefficient as a feedforward variable to fine-tune the heating power or gas flow distribution in each zone. This ensures that the actual temperature and oxygen partial pressure within the entire effective sintering zone remain within the effective range of the safe chemical potential window. Through the aforementioned adaptive calibration at the raw material end and dynamic compensation at the equipment end, process stability is transferred from an ideal laboratory environment to a complex industrial environment.

[0037] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A multilayer composite ceramic-metal encapsulation method for high-temperature pressure sensors, comprising a stacking construction step, wherein a metallized functional layer is printed on a ceramic green tape layer according to a preset circuit layout and laminated to construct a composite green unit, and a rheological matching co-firing step is performed on the composite green unit, characterized in that, The rheological matching co-firing process includes: When the sintering furnace temperature enters the maximum shrinkage rate temperature range of the metallized functional layer, an atmosphere chemical potential pinning operation is performed. By adjusting the volume flow ratio of hydrogen to water vapor in the process gas introduced into the sintering furnace, the furnace atmosphere dew point temperature is raised from the reduction set value to the pinning set value. The oxygen partial pressure in the furnace corresponding to the pinning set value is in the metastable range on the redox reaction equilibrium boundary of the metallized functional layer. The adsorbed oxygen atoms generated by the dissociation of water molecules in the atmosphere occupy the active sites on the grain surface of the metallized functional layer to suppress its surface diffusion, while keeping the metallized functional layer in a non-oxidized state. Maintain the pinning setting until the difference in instantaneous linear shrinkage between the metallized functional layer and the ceramic green tape layer converges to the preset synchronization threshold, and restore the atmosphere dew point temperature to the reduction setting.

2. The multilayer composite ceramic-metal encapsulation method for a high-temperature pressure sensor according to claim 1, characterized in that, The reduction setting is below -40 degrees Celsius, and the pinning setting is between -10 degrees Celsius and +20 degrees Celsius. The operation of adjusting the volume flow ratio of hydrogen and water vapor in the process gas introduced into the sintering furnace includes introducing a wet hydrogen gas flow that has been wetted by a constant temperature water bath through a mass flow controller and mixing it with a dry hydrogen gas flow to establish a surface energy level control environment dominated by water vapor partial pressure in the maximum shrinkage rate temperature range.

3. The multilayer composite ceramic-metal encapsulation method for a high-temperature pressure sensor according to claim 1, characterized in that, The rheological matching co-firing step also includes performing a differential discharge operation of organic matter during the low-temperature debinding stage. The discharge operation is carried out in the temperature range of 200 degrees Celsius to 500 degrees Celsius. Based on the time axis misalignment between the decomposition kinetics of the organic carrier in the metallized functional layer and the volatilization kinetics of the plasticizer in the ceramic green belt layer, the oxygen partial pressure in the furnace is periodically adjusted to establish a porous skeleton channel of the ceramic matrix before the metallized functional layer undergoes violent degassing.

4. The multilayer composite ceramic-metal encapsulation method for a high-temperature pressure sensor according to claim 1, characterized in that, The rheological matching co-firing step also includes performing reverse thermal expansion differential coupling cooling during the cooling phase, which reduces the instantaneous cooling rate during the cooling process. The function is defined as the inverse correlation function of the absolute value of the difference between the coefficients of thermal expansion of the ceramic green layer and the metallized functional layer at the current temperature T: ,in, Let be the instantaneous thermal expansion coefficient of the ceramic green ribbon layer at temperature T. Let T be the instantaneous thermal expansion coefficient of the metallized functional layer at temperature T, and K be a preset cooling efficiency constant. It is a non-zero numerical stability factor; in For temperature zones exceeding a preset difference threshold, the instantaneous cooling rate, determined by a function, is limited to below a preset safe rate.

5. A multilayer composite ceramic-metal encapsulation method for a high-temperature pressure sensor according to claim 1, characterized in that, The maximum shrinkage rate temperature range is determined through a pre-sintering thermal analysis step, which includes: obtaining the thermal shrinkage differential curves of the metallized functional layer and the ceramic green tape layer in the current batch, identifying the characteristic temperature point in the thermal shrinkage differential curve where the first derivative of the shrinkage rate is zero, and mapping the characteristic temperature point to the trigger temperature of the initiation atmosphere chemical potential pinning operation in the rheological matching co-firing step.

6. The multilayer composite ceramic-metal encapsulation method for a high-temperature pressure sensor according to claim 1, characterized in that, The metastable region is defined based on the oxidation thermodynamic data of the metal components in the metallized functional layer. The oxygen partial pressure corresponding to the pinning set value is between the equilibrium oxygen partial pressure for the metal components to form the lowest valence oxide and the reduction limit oxygen partial pressure for the metal components to maintain the metallic state. A diffusion barrier film with a thickness of less than five atomic layers is formed at the grain boundary of the metallized functional layer.

7. A multilayer composite ceramic-metal encapsulation method for a high-temperature pressure sensor according to claim 1, characterized in that, The metallized functional layer is selected from tungsten, molybdenum, or a tungsten-molybdenum alloy, and the ceramic strip layer is selected from alumina or aluminum nitride; the preset synchronization threshold is set to a linear shrinkage rate difference of 0.1 percent per minute. After completing the atmosphere chemical potential pinning operation, the rheological matching co-firing step continues to raise the temperature to the highest densification temperature of 1,500 to 1,650 degrees Celsius.

8. A multilayer composite ceramic-metal encapsulation method for a high-temperature pressure sensor according to claim 4, characterized in that, The reverse thermal expansion differential coupling cooling operation also includes locking the instantaneous cooling rate at a constant low rate when the furnace temperature passes through the plastic-brittle transition temperature range of the metallized functional layer, and maintaining this low rate until a transition layer with a chemical gradient is formed at the interface between the metallized functional layer and the ceramic green belt layer through atomic interdiffusion.

9. A multilayer composite ceramic-metal encapsulation method for a high-temperature pressure sensor according to claim 1, characterized in that, The multilayer composite ceramic-metal package structure is a housing base with three-dimensional wiring capability. The metallized functional layer includes buried circuits formed between ceramic green tape layers and vertical interconnect vias penetrating the ceramic green tape layers. Atmospheric chemical potential pinning operation suppresses the planar shrinkage of the metallized functional layer while simultaneously suppressing the radial shrinkage of the metal filler in the vertical interconnect vias through the action of isotropic chemical potential.

10. A multilayer composite ceramic-metal encapsulation method for a high-temperature pressure sensor according to claim 1, characterized in that, The rheological matching co-firing step adopts a compensation logic based on the specific surface area of ​​the raw materials. When the specific surface area of ​​the raw materials of the metallized functional layer increases, resulting in improved sintering activity, the dew point temperature of the pinning set value is increased or the time of maintaining the pinning set value is extended to compensate for the shrinkage rate deviation caused by the change in the activity of the raw materials.

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