Gallium indium tin alloy negative pressure vacuum filling system

Abstract

The invention discloses a gallium-indium-tin alloy negative pressure vacuum filling system, and belongs to the technical field of precise instrument manufacturing. The system comprises an alloy preparation unit, a vacuum generation unit, a filling control unit, a quality monitoring unit, a waste gas treatment unit and a central control system. Alloy oxidation is prevented through full-process inert gas protection, bubble-free precise filling is realized by adopting a multi-stage vacuum and self-adaptive negative pressure control strategy, and the filling consistency and reliability are ensured by integrating multi-sensor quality monitoring. The system effectively solves the toxic pollution problem of traditional mercury filling, overcomes the filling problems that gallium-indium-tin alloy is high in viscosity and prone to oxidation, is mainly applied to mercury-free manufacturing of precision instruments such as pressure sensors and medical instruments, and has the advantages of being high in precision, high in safety, environmentally friendly, high in adaptability and the like.

Description

Technical Field

[0001] This invention relates to the fields of precision instrument manufacturing and special alloy processing technology, specifically to a special system for accurately, non-oxidizing, and bubble-free filling of low-melting-point, easily oxidized liquid gallium indium tin alloy into the cavity of micro-miniature devices under vacuum or negative pressure environment, and in particular to a gallium indium tin alloy negative pressure vacuum filling system. Background Technology

[0002] In the field of precision instrument manufacturing, such as pressure sensors, temperature sensors, and medical blood pressure monitors, it is often necessary to fill the tiny cavities or capillaries inside the devices with functional liquid media to transmit physical signals such as pressure and temperature. Traditionally, mercury has been widely used as such a filling medium due to its unique physicochemical properties (such as a wide liquid range, high density, and stable surface tension).

[0003] However, mercury and its compounds are highly toxic and bioaccumulative, posing a serious threat to the health of operators, and their production, use, and disposal all carry significant environmental pollution risks. With increasing global environmental awareness and the entry into force of the international Minamata Convention on Mercury, finding mercury alternatives and developing corresponding non-toxic filling processes has become an urgent need for the industry.

[0004] Gallium-based alloys, especially gallium-indium-tin alloys (typically low-melting-point eutectic alloys with gallium comprising approximately 68-85%, indium approximately 10-25%, and tin approximately 5-10%, with melting points usually below 20°C), are considered ideal alternatives to mercury due to their non-toxicity, wide liquid range, and good electrical and thermal conductivity. Their excellent wettability (to glass, ceramics, various metals, and polymers) and low physiological toxicity make them particularly valuable in medical devices and wearable devices. However, a series of technical challenges exist in the practical application of gallium-based alloys as fillers, limiting their large-scale and consistent application in high-precision devices. 1. Extreme susceptibility to oxidation: When gallium-based alloys are exposed to air, even at room temperature, a dense and tough oxide film (mainly amorphous gallium oxide Ga2O3) rapidly forms on their surface. This oxide film not only significantly increases the apparent viscosity of the alloy, forming a semi-solid "jelly"-like substance that severely hinders its flowability, leading to incomplete filling or blockage of microchannels (especially when the channel size is less than 0.5 mm), but once formed, the oxide film is difficult to completely remove using conventional physical methods, remaining at the filling interface and affecting the reliability of electrical contacts or the stability of signal transmission in the device.

[0005] 2. High viscosity and complex wetting behavior: Compared to mercury, some gallium-based alloys can have viscosity several orders of magnitude higher near room temperature. For example, the viscosity of pure liquid gallium is approximately 0.002 Pa·s, while the viscosity of gallium indium tin oxide alloy formed upon contact with air can rise sharply to 0.1 Pa·s or even higher. This high viscosity, combined with its complex wetting properties with different materials (such as stainless steel, silicon, glass, and epoxy resin) (contact angles ranging from a few degrees to hundreds of degrees), makes it difficult to achieve complete, defect-free filling in micron- or submillimeter-scale capillaries or cavities using gravity or simple positive pressure. Inappropriate wetting can lead to discontinuous filling, voids, or "stringing" phenomena.

[0006] 3. Bubble Control Challenge: During the filling process, if gases (including air, vaporized moisture, or trace amounts of dissolved gases released by the alloy itself) are pre-existing in the device cavity, flow channel, or molten alloy, or are entrained during the process, bubbles can easily form. These bubbles are difficult to expel from the closed cavity, severely affecting the measurement accuracy, response speed, stability, and lifespan of sensors and other devices. For MEMS devices, the presence of microbubbles can lead to localized stress concentration, increased thermal resistance, or electrical signal distortion.

[0007] 4. Extremely High Requirements for Filling Accuracy and Consistency: Modern precision devices, especially microelectromechanical systems (MEMS) sensors and implantable medical devices, have extremely high requirements for the volume, mass, positional accuracy of the filling medium, as well as the physical properties (such as density uniformity and absence of internal stress) after filling. For example, some high-precision pressure sensors require the volume error of the filling medium to be less than ±1%, and absolutely free of visible air bubbles. Traditional, extensive filling methods that rely on operator experience cannot meet these repeatable and highly consistent industrial production requirements.

[0008] 5. Process Compatibility and System Integration Safety: A fully enclosed, automated system is needed that is compatible with the alloy's easy oxidation and high viscosity characteristics, achieving oxidation prevention and precise control of the filling process throughout the entire process from alloy melting, storage, transportation to filling, while ensuring operational safety and environmental friendliness. Existing technologies often only focus on a single aspect, lacking system-level integration and collaborative optimization.

[0009] Existing technologies include some filling devices for liquid metals or other media, but they typically fail to systematically solve all the problems associated with filling gallium indium tin alloys. For example: Some equipment lacks effective inert gas protection throughout the entire process, or only provides local protection in critical areas, failing to create a complete protective atmosphere from raw materials to finished products, which leads to oxidation of the alloy during transfer and waiting for filling.

[0010] Some vacuum control methods are crude, using a single, fixed vacuum level, which cannot adapt to the different requirements of driving force and flow state at different stages of the filling process (such as rapid filling, stable filling, and fine sealing). This can easily lead to turbulent air entrapment at the beginning of filling or overfilling and overflow at the end.

[0011] Some systems lack high-precision flow and process monitoring, relying solely on time or experience to determine the filling endpoint, making it difficult to guarantee the consistency and quality of filling, and even more difficult to achieve adaptive parameter adjustment based on real-time feedback.

[0012] Some systems lack flexibility, and key components such as filling heads are not easy to replace, making it difficult to quickly adapt to workpieces of different shapes, sizes, and interfaces, thus affecting production efficiency and equipment utilization.

[0013] Most existing solutions do not adequately consider waste gas treatment, which may cause pollution of the working environment or slight loss of alloy components.

[0014] Therefore, there is an urgent need in this field for an integrated, automated, high-precision, and highly flexible dedicated filling system that can effectively overcome the bottlenecks in gallium indium tin alloy filling technology, safely, efficiently, and consistently replace the traditional mercury filling process, and meet the stringent requirements of modern precision manufacturing for environmental protection, quality, and efficiency. Summary of the Invention

[0015] In view of the above-mentioned shortcomings of the existing technology, the primary objective of the present invention is to overcome the shortcomings of the existing technology and provide a gallium indium tin alloy negative pressure vacuum filling system. This system can realize the oxidation-free preparation, storage and transportation of gallium indium tin alloy under the protection of inert gas throughout the process, fundamentally eliminating the adverse effects of oxide film on the filling process and the performance of the final product.

[0016] Another objective of this invention is to provide a gallium indium tin alloy negative pressure vacuum filling system that can precisely control the negative pressure environment and adopt an adaptive control strategy to achieve bubble-free precision filling of complex structures from microliter to milliliter levels.

[0017] Another objective of this invention is to provide a gallium indium tin alloy negative pressure vacuum filling system with functions such as full-process multi-sensor quality monitoring, adaptive parameter adjustment based on real-time feedback, online defect diagnosis and alarm, and environmentally friendly waste gas treatment, so as to ensure the controllability of the filling process and the traceability of the results.

[0018] Another objective of this invention is to provide a modular, adaptable, and highly flexible gallium indium tin alloy negative pressure vacuum filling system that can be applied to the filling needs of various precision devices such as pressure sensors, medical devices, MEMS devices, and flexible electronics, thereby reducing equipment investment and conversion costs.

[0019] To achieve the above objectives, the present invention adopts the following technical solution: A gallium indium tin alloy negative pressure vacuum filling system, comprising the following units connected in sequence and controlled by a central control system: Alloy preparation unit: Used for melting, stirring, homogenizing, and storing liquid gallium indium tin alloy in a pre-defined proportion under an inert gas protective environment. This unit includes an inert gas-protected reactor with a precisely temperature-controlled heating system and a high-efficiency stirring mechanism; a composition monitoring instrument for online monitoring of alloy composition uniformity (e.g., a conductivity meter based on eddy current principle or a densitometer based on gamma rays); and an alloy storage tank with a highly efficient double-layer vacuum insulation structure and a special anti-adhesion coating on the inner wall. The storage tank is equipped with a high-precision temperature control system, enabling the gallium indium tin alloy to be precisely maintained within a wide liquid operating temperature range (e.g., -32°C to 200°C, preferably 25°C to 80°C to balance fluidity and oxidation tendency), and can be configured with slow or rapid cooling functions as needed to adapt to the solidification characteristics of different alloys.

[0020] Vacuum Generation Unit: This unit provides and maintains a highly stable, dynamically adjustable negative pressure environment for the filling chamber. It includes a multi-stage vacuum pump system consisting of a primary pump (such as an oil vane pump or a dry piston pump) and a secondary pump (such as a turbomolecular pump, a Roots pump, or a dry vortex pump); a vacuum buffer tank to stabilize pressure and reduce pulsation; a dust filter to protect the vacuum pump from particulate contamination; and a digital pressure sensor (preferably an absolute pressure sensor with a range of 0 to 760 mmHg and an accuracy better than 0.5%FS) for real-time, high-precision monitoring of the vacuum level in the filling chamber. Through a PLC-based or industrial computer-based vacuum controller, based on feedback signals from the digital pressure sensor and a pre-set complex control algorithm, this unit adaptively and precisely adjusts and stabilizes the vacuum level in the filling chamber within a preset range (e.g., 200-400 mmHg) at any target value.

[0021] Filling Control Unit: As the core actuator of the system, this unit precisely and controllably delivers and fills the tiny cavities of the workpiece with gallium indium tin alloy. This unit includes a quick-change modular filling head (with a standardized interface supporting filling tubes of different lengths, inner diameters, and materials), integrated miniature precision valves (such as piezoelectric ceramic valves, voice coil motor-driven valves, or servo-electric needle valves, with a response time of less than 10ms and high flow resolution), extremely fine (0.1-0.5mm) capillary filling tubes (whose inner walls can be ultra-polished and coated with diamond-like carbon (DLC) or titanium nitride (TiN) to further reduce flow resistance and prevent alloy adhesion), and a high-precision flow monitoring and control system (using flow meters based on the Coriolis principle or micro-turbines, monitoring and controlling flow rates in the range of 0.1-10 mL / min with a control accuracy of ±1%). The unit is flexibly designed and can employ negative pressure suction, positive pressure push, or a combination of positive and negative pressure methods to fill workpieces according to process requirements.

[0022] Quality Monitoring Unit: This unit monitors the filling process status and evaluates the filling quality in real time and from multiple dimensions. It employs multi-sensor information fusion technology, including a high-resolution, high-speed visual inspection subsystem (equipped with appropriate lighting, such as backlighting or coaxial lighting, to enhance contrast) for visual inspection of the filling process, liquid level, macroscopic bubbles, and surface oxidation; an ultrasonic inspection subsystem (operating at frequencies typically in the 1-20MHz range) for non-invasive monitoring of the alloy's flow front position and velocity within the workpiece and for detecting internal microbubbles (up to tens of micrometers in size); and distributed multi-point pressure and temperature sensors for monitoring key parameters of the filling environment (such as chamber pressure, alloy temperature, and ambient temperature). All sensor data is transmitted to the central control system in real time. The system's built-in adaptive algorithms (e.g., based on fuzzy logic, PID control, or trained neural network models) analyze and process the data, dynamically adjusting filling parameters (such as vacuum level, filling rate, and alloy temperature). It also features online automatic defect detection, classification, and immediate alarm functions.

[0023] Exhaust gas treatment unit: Used to safely collect and treat trace amounts of volatile substances, alloy vapors, or oxygen-containing exhaust gases that may be generated during the filling process or discharged during the cavitation phase. This unit typically includes a condensation recovery unit (using semiconductor refrigeration or circulating coolant to reduce the exhaust gas temperature to below 0°C, effectively condensing and recovering low vapor pressure metal components such as gallium and indium) connected in sequence, and a high-efficiency activated carbon adsorption unit (using impregnated activated carbon or multi-stage filter beds to adsorb any trace organic volatiles and extremely fine particulate matter that may be present), ensuring that the gas emitted into the exhaust is clean and meets environmental protection and occupational health and safety standards.

[0024] Central Control System: As the brain of the system, it communicates with all the aforementioned units (typically via industrial Ethernet, ProfiBUS, EtherCAT, or other fieldbus networks) to coordinate and control the orderly and collaborative operation of each unit. The central control system is built on a highly reliable programmable logic controller (PLC) or industrial PC (IPC) and is equipped with a graphical human-machine interface (HMI) for process parameter setting, process flow visualization, real-time data and curve display, alarm management, and historical data retrieval. The system also integrates a data logging module to automatically record all key process parameters, equipment status, quality inspection results, and alarm events, forming a complete and tamper-proof production data package, achieving traceability throughout the entire production process.

[0025] Preferably, the vacuum generation unit employs a PLC-based vacuum controller configured to execute an adaptive negative pressure control strategy. This strategy differs from simple setpoint control; instead, it dynamically adjusts the target vacuum level based on the characteristics of different stages of the filling process. For example, in the initial filling stage, a first relatively high vacuum level (e.g., close to 400 mmHg) is used to generate a larger driving force, ensuring the alloy starts quickly and fills the main channel; when the alloy liquid flow is close to filling the workpiece cavity, it switches to a second relatively low vacuum level (e.g., 250-300 mmHg) to slow the flow rate, avoiding overfilling or overflow due to inertia, and achieving precise liquid level control; and / or, for workpieces with complex microstructures, large depth-to-width ratios, or areas dominated by capillary forces, periodically alternating pulsed negative pressure within the 200-400 mmHg range can be used for filling, utilizing the "micro-vibration" effect generated by pressure fluctuations to help the alloy overcome local resistance, expel trapped gas, and improve filling integrity.

[0026] More preferably, the visual inspection subsystem and the ultrasonic inspection subsystem in the quality monitoring unit can work together. For example, when the visual system detects an abnormal oxide film in the filling port area, it can trigger an alarm and prompt the user to check or replace the inert gas; when the ultrasonic system detects stagnation at the flow front or detects a suspected bubble signal, it can link with the central control system to automatically attempt to adjust the vacuum level or trigger a pulse mode, and record the event for subsequent workpiece quality analysis.

[0027] The system's workflow is based on the principle of negative pressure filling and integrates positive pressure assistance and intelligent control. It mainly includes the following steps: system preparation and alloy pretreatment (including system self-check, inert atmosphere establishment, alloy melting and filtration); workpiece clamping and sealing (ensuring positioning accuracy and sealing reliability); system vacuuming and leak detection (achieving the preset vacuum level and confirming system tightness); alloy filling and dynamic parameter adjustment (a core step, optimizing the filling process in real time based on multi-sensor feedback); filling port sealing and curing (using methods such as laser welding, cold welding, or epoxy sealing to seal the filling port promptly and controlling curing conditions); post-processing and cleaning (cleaning the workpiece surface and purging the system flow channels); quality inspection and data recording (online and offline combined quality assessment and data archiving); system maintenance and preparation for the next filling.

[0028] The above-mentioned objective of this invention is achieved through the following technical solutions: This invention provides a gallium indium tin alloy negative pressure vacuum filling system, comprising: an alloy preparation unit (100) for preparing and storing liquid gallium indium tin alloy under an inert gas protective environment; a vacuum generation unit (200) for providing and maintaining a stable negative pressure environment for the filling chamber; a filling control unit (300) for accurately filling the liquid gallium indium tin alloy into the workpiece under the negative pressure environment; a quality monitoring unit (400) for real-time monitoring of the filling process and quality, and feedback control of filling parameters; an exhaust gas treatment unit (500) for treating the exhaust gas generated during the filling process; and a central control system (600) for communicating with the alloy preparation unit (100), the vacuum generation unit (200), the filling control unit (300), the quality monitoring unit (400), and the exhaust gas treatment unit (500), for controlling the coordinated operation of each unit.

[0029] According to one embodiment of the present invention, the alloy preparation unit (100) includes: an inert gas protected reactor (110), which is internally equipped with a heating system (111), a stirring mechanism (112), and a composition monitor (113); and an alloy storage tank (120) with a double-layer heat-insulating structure and an anti-adhesion coating on the inner wall; wherein the alloy storage tank (120) is connected to a temperature control system for maintaining the gallium indium tin alloy in a liquid temperature range between -32°C and 200°C. Preferably, the anti-adhesion coating is one of diamond-like carbon (DLC) coating, titanium nitride (TiN) coating, or Teflon (PTFE) coating, with a surface roughness Ra of less than 0.2 μm, to minimize alloy adhesion and residue. The composition monitor (113) is preferably an online conductivity meter, which indirectly determines whether the main components have segregated or oxidized by monitoring changes in the alloy's conductivity.

[0030] According to one embodiment of the present invention, the vacuum generation unit (200) includes: a multi-stage vacuum pump system, including a primary rotary vane pump (210) and a high-level molecular pump (220); a vacuum buffer tank (230) connected between the multi-stage vacuum pump system and the filling chamber; a dust filter device (240) disposed at the front end of the vacuum buffer tank (230); a digital pressure sensor (250) for real-time monitoring of the vacuum level of the filling chamber; and a PLC-based vacuum controller for adaptively adjusting the vacuum level of the filling chamber within the range of 200-400 mmHg based on the feedback signal from the digital pressure sensor (250) and a preset program. The volume of the vacuum buffer tank (230) is preferably 5-20 times the volume of the filling chamber to effectively suppress pressure fluctuations. The filtration accuracy of the dust filter device (240) is preferably 0.1 μm to prevent fine oxide particles from entering the vacuum pump system.

[0031] According to one embodiment of the present invention, the PLC-based vacuum controller is configured to execute an adaptive negative pressure control strategy, which includes: employing a first higher vacuum level during the initial filling stage; employing a second lower vacuum level when the alloy is close to filling the workpiece; and / or, for workpieces with complex microstructures, employing a periodically alternating pulsed negative pressure within the range of 200-400 mmHg. The period of the pulsed negative pressure is preferably 0.5 seconds to 5 seconds, and the duty cycle is adjustable between 30% and 70%, precisely controlled by a PLC program to produce an optimal "micro-vibration" filling effect.

[0032] According to one embodiment of the present invention, the filling control unit (300) includes: a modular filling head (310) equipped with a miniature precision valve and a capillary filling tube with an inner diameter of 0.1-0.5 mm; and a high-precision flow monitoring and control system (320) for monitoring and controlling the filling flow rate within the range of 0.1-10 mL / min. The filling control unit (300) is capable of filling using a negative pressure method, a positive pressure method, or a combination of positive and negative pressure methods. The capillary filling tube is preferably made of 316L stainless steel, Hastelloy, or a quartz glass tube with a DLC coating on the inner wall, providing strength, corrosion resistance, and anti-adhesion properties. The modular filling head (310) is connected to the main delivery pipeline via a quick-change connector, with a replacement time of less than 2 minutes, significantly improving the equipment's adaptability to different workpieces.

[0033] According to one embodiment of the present invention, the quality monitoring unit (400) employs multi-sensor fusion technology and includes: a visual inspection subsystem (410) for detecting bubbles and oxidation during the filling process; an ultrasonic inspection subsystem (420) for non-invasive monitoring of the flow state of the alloy inside the workpiece; and pressure and temperature sensors (430) for monitoring filling environment parameters. The central control system (600) receives data from the multiple sensors and dynamically adjusts the filling parameters using a built-in adaptive algorithm, and also has online defect detection and alarm functions. The visual inspection subsystem (410) is preferably equipped with a high-speed industrial camera with a resolution of 2 megapixels or higher and a frame rate of not less than 100fps, and is paired with a blue LED coaxial light source with a wavelength of 450-470nm to enhance the observation capability of alloy flow within transparent or semi-transparent workpieces. The ultrasonic inspection subsystem (420) preferably operates at a frequency of 5-15MHz, which can be adjusted according to the workpiece wall thickness and material to achieve effective detection of internal flow and microbubbles (diameter > 50μm).

[0034] According to one embodiment of the present invention, the waste gas treatment unit (500) includes a condensation recovery device (510) and an activated carbon adsorption device (520) connected in sequence for removing alloy vapors and volatile organic compounds from the waste gas. The condensation temperature of the condensation recovery device (510) is preferably set between -10°C and -20°C to ensure effective condensation and capture of components such as gallium and indium. The activated carbon adsorption device (520) is equipped with a differential pressure monitor; when the differential pressure exceeds a set threshold, the central control system (600) will issue a replacement warning.

[0035] According to one embodiment of the present invention, the central control system (600) includes a programmable logic controller (PLC) (610), a human-machine interface (HMI) (620), and a data recording module, used to realize automated system operation, process parameter setting, real-time status monitoring, and production data traceability. The data recording module can record full-process data, including vacuum curves, flow curves, temperature curves, keyframes of visual inspection images, ultrasonic signal characteristic values, and alarm logs, with a storage time of no less than 3 years. It also supports rapid retrieval and export by workpiece batch number, meeting the stringent quality traceability requirements of high-end manufacturing.

[0036] The present invention also provides a method for negative pressure vacuum filling of gallium indium tin alloy using the system described in any one of claims 1-8, characterized by comprising the following steps: System preparation and alloy pretreatment steps (S101): Under inert gas protection, the gallium indium tin alloy is heated to liquid state and filtered; Workpiece clamping and sealing step (S102): Install the workpiece to the filling station and seal it to form a filling chamber; System vacuuming and leakage detection steps (S103): Vacuum the filling chamber and the inside of the workpiece to a preset negative pressure and perform leakage detection; Alloy filling and parameter adjustment steps (S104): Liquid gallium indium tin alloy is filled into the workpiece under negative pressure difference, and the filling parameters are dynamically adjusted according to the quality monitoring signal; Filler port sealing and curing step (S105): Seal the filler port of the workpiece and restore the chamber to normal pressure; Post-processing and quality inspection steps (S106): Clean the workpiece and inspect and record the filling quality.

[0037] According to one embodiment of the present invention, in the alloy filling and parameter adjustment step (S104), the filling vacuum degree is dynamically adjusted between 200 mmHg and 400 mmHg according to the filling process, and / or a pulsed negative pressure that periodically alternates between 200 mmHg and 400 mmHg is used for filling. In the filling port sealing and curing step (S105), the sealing preferably employs low-heat-input laser micro-welding technology, with a laser power of 10-50 W, a pulse width of 1-10 ms, and a focused spot diameter of less than 100 μm, to ensure rapid and reliable sealing with minimal thermal impact on the surrounding area. The process of restoring atmospheric pressure preferably employs a staged and slow filling of inert gas, with the pressure recovery rate controlled at 10-50 kPa / min, to avoid sudden pressure changes impacting the incompletely cured alloy or the fragile structure of the workpiece.

[0038] In summary, compared with the prior art, the present invention includes at least one of the following beneficial technical effects: 1. Environmental Safety and Health Protection: The use of non-toxic gallium indium tin alloy completely replaces highly toxic mercury, fundamentally eliminating harm to operators and the environment. A fully enclosed alloy processing flow, a highly efficient waste gas treatment system, and a systematic safety interlock design further ensure the safety and cleanliness of the entire production process, aligning with green manufacturing and sustainable development principles.

[0039] 2. Extremely high filling accuracy and excellent product consistency: Through a multi-level adjustable vacuum system, micro high-precision capillary filling technology, real-time flow monitoring, and model-based adaptive filling algorithm, precise volume control from micro-level to milliliter level is achieved. The filling volume accuracy is 3-5 times higher than traditional methods, typically within ±1%, effectively ensuring a high degree of consistency in the performance of batch products and meeting the stringent requirements of high-end precision devices.

[0040] 3. Excellent oxidation prevention effect: From alloy raw material smelting, constant temperature storage, and closed transportation to the filling chamber, the entire process is carried out under strict control of inert gas (such as high-purity argon and nitrogen), effectively isolating oxygen and reducing the oxidation weight gain rate of the alloy by more than 90% throughout the process (actual measurement can be less than 0.01%), significantly improving the purity and fluidity of the filling medium and the electrical contact reliability and long-term life of the final product.

[0041] 4. Revolutionary bubble control capability: Through multi-stage vacuum degassing, gradient pressure filling technology, pulse negative pressure assisted degassing, and optimized low-turbulence flow channel design, the alloy is ensured to be filled smoothly in a laminar or quasi-laminar state, and the internal bubble rate of the product is stably controlled below 0.1%, which is far lower than the 3-5% commonly found in traditional methods. It can even achieve "zero bubble" filling, which greatly improves the measurement accuracy and stability of the device.

[0042] 5. High system adaptability and production flexibility: The modular design of the system (especially the quick replacement of the filling head), the wide range of adjustable process parameters (vacuum, temperature, flow rate, pulse mode), and the compatibility with multiple filling methods (negative pressure, positive pressure, positive and negative pressure combination) allow for rapid adaptation and process optimization according to the material, geometry, cavity structure, and capacity requirements of different devices. The applicable scope covers a variety of precision devices, from traditional pressure sensors to emerging MEMS chips and flexible strain sensors, significantly reducing production line modification and equipment investment costs.

[0043] 6. Automation, Intelligence, and Traceability: An integrated central control system and multi-sensor quality monitoring throughout the entire process enable a high degree of automation in the filling process and intelligent decision-making based on real-time feedback. This reduces reliance on operator experience and improves production efficiency and first-pass yield (expected to increase by over 15%). A comprehensive data recording and traceability system provides a solid data foundation for product quality analysis, process optimization, and fault diagnosis, aligning with the development direction of intelligent factories.

[0044] 7. Significant economic benefits: Although the initial equipment investment may be higher than that of traditional equipment, the entire system has significant comprehensive economic benefits throughout its entire life cycle by improving product yield, reducing scrap, reducing precious metal alloy loss, avoiding high mercury pollution treatment costs, and saving labor due to increased production automation. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the overall structure of the gallium indium tin alloy negative pressure vacuum filling system of the present invention.

[0046] Figure 2 This is a detailed structural diagram of the alloy preparation unit of the present invention.

[0047] Figure 3 This is a schematic diagram of the working principle of the vacuum generation unit of the present invention.

[0048] Figure 4 This is a schematic diagram of the filling control unit of the present invention.

[0049] Figure 5 This is a flowchart of the system workflow of the present invention.

[0050] Figure 6 This is a block diagram of the quality inspection system of the present invention.

[0051] Figure 7 This is a flowchart of the waste gas treatment unit of the present invention.

[0052] Figure 8 This is a diagram of the control system architecture of the present invention.

[0053] Reference numerals: 100, Alloy preparation unit; 110, Inert gas protected reactor; 111, Heating system; 112, Stirring mechanism; 113, Composition monitor; 120, Alloy storage tank; 200, Vacuum generation unit; 210, Primary rotary vane pump; 220, Advanced molecular pump; 230, Vacuum buffer tank; 240, Dust filtration device; 250, Digital pressure sensor; 300, Filling control unit; 310, Modular filling head; 320, High-precision flow monitoring and control system; 400, Quality monitoring unit; 410, Visual inspection subsystem; 420, Ultrasonic inspection subsystem; 430, Pressure and temperature sensor; 500, Waste gas treatment unit; 510, Condensation recovery device; 520, Activated carbon adsorption device; 600, Central control system; 610, Programmable Logic Controller (PLC); 620, Human-Machine Interface (HMI). Detailed Implementation

[0054] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0055] This invention discloses a gallium indium tin alloy negative pressure vacuum filling system, which includes the following units sequentially connected and controlled by a central control system 600: Alloy preparation unit 100: Used for melting, stirring, and storing liquid gallium indium tin alloy according to a preset ratio under an inert gas protective environment. This unit includes an inert gas protected reactor 110 with a heating system 111 and a stirring mechanism 112, a composition monitor 113, and a special stainless steel storage tank with a double-layered heat-insulating and anti-adhesion coating on the inner wall. The storage tank is equipped with a temperature control system to maintain the alloy within the operating temperature range (e.g., -32°C to 200°C). The inlet of the inert gas protected reactor 110 is equipped with a mass flow controller (MFC) to precisely control the inert gas flow rate, ensuring that the internal micro-positive pressure environment is stable within the range of 0.05-0.15 MPa (gauge pressure). The stirring mechanism 112 preferably employs magnetic coupling stirring, with an adjustable speed within the range of 50-500 rpm, to avoid potential leakage points and contamination risks associated with mechanical seals.

[0056] Vacuum generation unit 200: This unit provides and maintains a stable negative pressure environment for the filling chamber. It includes a multi-stage vacuum pump system (such as a primary rotary vane pump 210 and an advanced molecular pump 220), a vacuum buffer tank 230, a dust filter 240, and a digital pressure sensor 250 for real-time monitoring of the vacuum level. The unit uses a PLC control system to stably maintain the vacuum level of the filling chamber within a preset range (e.g., 200-400 mmHg). The advanced molecular pump 220 is preferably an oil-free turbomolecular pump to achieve a clean vacuum environment and avoid oil vapor contamination. The digital pressure sensor 250 uses a combination of a capacitive thin-film gauge and a Pirani gauge to cover both low and high vacuum ranges, ensuring measurement accuracy across the entire range.

[0057] The filling control unit 300, as the core actuator of the system, is used to precisely control the delivery of gallium indium tin alloy to the workpiece being filled. This unit includes a miniature precision valve, a capillary filling tube with an inner diameter of 0.1-0.5 mm, a flow monitoring system, and a modular filling head 310 that can be quickly replaced. This unit supports positive pressure, negative pressure, or a combination of both methods for filling. The high-precision flow monitoring and control system 320 uses a Coriolis mass flow meter, whose measurement is unaffected by changes in fluid density and viscosity, making it particularly suitable for fluids like gallium indium tin alloy whose properties change with temperature and oxidation levels.

[0058] Quality monitoring unit 400: Used for real-time monitoring of the filling process and evaluation of filling quality. This unit employs multi-sensor fusion technology, including a high-resolution camera for visual inspection of bubbles and oxidation, an ultrasonic detector for evaluating the alloy flow state, and pressure and temperature sensors 430 for monitoring environmental parameters. Data is collected by the central control system 600, which dynamically adjusts filling parameters through an adaptive algorithm and has online defect detection capabilities. The data processing algorithm built into the central control system 600 can perform time-frequency analysis on the ultrasonic signals, extracting characteristic frequencies related to the flow front velocity and bubble presence, thereby achieving more accurate internal state judgment.

[0059] Waste gas treatment unit 500: Used to collect and treat trace amounts of volatile substances or alloy vapors that may be generated during the filling process. This unit typically includes an activated carbon adsorption device 520, a condensation recovery device 510, etc., to ensure that emissions meet environmental standards. The condensation recovery device 510 uses Peltier semiconductor refrigeration chips for cooling, which has the advantages of compact structure, no moving parts, and precise temperature control.

[0060] Preferably, the central control system 600 is built on a programmable logic controller (PLC) and a human-machine interface (HMI), and integrates a data logging module to record all key process parameters and quality inspection results, forming a traceable production data package. The HMI interface is designed with access control functions, allowing different levels of operators to have different parameter modification and system operation permissions, ensuring process safety.

[0061] The system's workflow is based on the principle of negative pressure filling and mainly includes the following steps: system preparation and alloy pretreatment; workpiece clamping and sealing; system vacuuming and leak detection; alloy filling and parameter adjustment; filling port sealing and curing; post-processing and cleaning; quality inspection and data recording; system maintenance and preparation for the next filling.

[0062] Specifically, the vacuum generation unit 200 employs an adaptive negative pressure control strategy, dynamically adjusting the vacuum level according to different stages of the filling process. For example, a higher vacuum level (e.g., approximately 400 mmHg) is used in the initial filling stage to ensure rapid filling, while the vacuum level is gradually reduced (e.g., approximately 300 mmHg) as the alloy nears full filling to avoid overfilling. For particularly fine microstructures, pulsed negative pressure can be used. The waveform of the pulsed negative pressure can be a square wave, sawtooth wave, or sine wave. The specific waveform and parameters can be determined through process experiments based on the workpiece structure and stored in the formula library of the central control system.

[0063] This invention provides a gallium indium tin alloy negative pressure vacuum filling system, comprising: an alloy preparation unit 100 for preparing and storing liquid gallium indium tin alloy under an inert gas protective environment; a vacuum generation unit 200 for providing and maintaining a stable negative pressure environment for the filling chamber; a filling control unit 300 for accurately filling the liquid gallium indium tin alloy into the workpiece under negative pressure; a quality monitoring unit 400 for real-time monitoring of the filling process and quality, and feedback control of filling parameters; an exhaust gas treatment unit 500 for treating the exhaust gas generated during the filling process; and a central control system 600, communicatively connected to the alloy preparation unit 100, the vacuum generation unit 200, the filling control unit 300, the quality monitoring unit 400, and the exhaust gas treatment unit 500, for controlling the coordinated operation of each unit.

[0064] The alloy preparation unit 100 includes: an inert gas protected reactor 110, which is equipped with a heating system 111, a stirring mechanism 112 and a composition monitoring instrument 113; and an alloy storage tank 120 with a double-layer heat preservation structure and an anti-adhesion coating on the inner wall; wherein, the alloy storage tank 120 is connected to a temperature control system for maintaining the gallium indium tin alloy in a liquid temperature range between -32°C and 200°C.

[0065] The vacuum generation unit 200 includes: a multi-stage vacuum pump system, including a primary rotary vane pump 210 and an advanced molecular pump 220; a vacuum buffer tank 230 connected between the multi-stage vacuum pump system and the filling chamber; a dust filter device 240 disposed at the front end of the vacuum buffer tank 230; a digital pressure sensor 250 for real-time monitoring of the vacuum level of the filling chamber; and a PLC-based vacuum controller for adaptively adjusting the vacuum level of the filling chamber within the range of 200-400 mmHg based on the feedback signal from the digital pressure sensor 250 and a preset program.

[0066] The PLC-based vacuum controller is configured to execute an adaptive negative pressure control strategy, which includes: using a first higher vacuum level during the initial filling stage; using a second lower vacuum level when the alloy is close to filling the workpiece; and / or, for workpieces with complex microstructures, using a pulsed negative pressure that alternates periodically in the range of 200-400 mmHg.

[0067] The filling control unit 300 includes: a modular filling head 310, which is equipped with a miniature precision valve and a capillary filling tube with an inner diameter of 0.1-0.5 mm; a high-precision flow monitoring and control system 320, used to monitor and control the filling flow rate in the range of 0.1-10 mL / min; wherein, the filling control unit 300 can fill using negative pressure method, positive pressure method or a combination of positive and negative pressure method.

[0068] The quality monitoring unit 400 employs multi-sensor fusion technology, including: a visual inspection subsystem 410 for detecting bubbles and oxidation during the filling process; an ultrasonic inspection subsystem 420 for non-invasive monitoring of the alloy flow state inside the workpiece; and pressure and temperature sensors 430 for monitoring filling environment parameters. The central control system 600 receives data from multiple sensors and dynamically adjusts the filling parameters through a built-in adaptive algorithm, and also has online defect detection and alarm functions.

[0069] The waste gas treatment unit 500 includes a condensation recovery device 510 and an activated carbon adsorption device 520 connected in sequence, used to remove alloy vapors and volatile organic compounds from the waste gas. The central control system 600 includes a programmable logic controller (PLC) 610, a human-machine interface (HMI) 620, and a data logging module, used to realize automated system operation, process parameter setting, real-time status monitoring, and production data traceability.

[0070] The present invention also provides a method for negative pressure vacuum filling of gallium indium tin alloy using the system of the above embodiments, comprising the following steps: System preparation and alloy pretreatment steps: Under inert gas protection, the gallium indium tin alloy is heated to a liquid state and then filtered; Workpiece clamping and sealing steps: Install the workpiece into the filling station and seal it to form a filling chamber; System vacuuming and leak detection steps: Vacuum the filling chamber and the inside of the workpiece to a preset negative pressure and perform leak detection; Alloy filling and parameter adjustment steps: Liquid gallium indium tin alloy is filled into the workpiece under negative pressure difference, and the filling parameters are dynamically adjusted according to the quality monitoring signal; Filler port sealing and curing steps: Seal the filler port of the workpiece and restore the chamber to normal pressure; Post-processing and quality inspection steps: Clean the workpiece and inspect and record the filling quality.

[0071] In the alloy filling and parameter adjustment steps, the filling vacuum degree is dynamically adjusted between 200 mmHg and 400 mmHg according to the filling process, and / or a pulsed negative pressure that alternates periodically between 200 mmHg and 400 mmHg is used for filling.

[0072] Example 1: System Overall Structure and Basic Workflow Reference Figure 1 The gallium indium tin alloy negative pressure vacuum filling system of this embodiment mainly consists of an alloy preparation unit 100, a vacuum generation unit 200, a filling control unit 300, a quality monitoring unit 400, a waste gas treatment unit 500, and a central control system 600.

[0073] The alloy preparation unit 100 is connected to the filling control unit 300 via a fully heated insulated pipeline. The outer layer of the pipeline is a stainless steel corrugated pipe, the inner layer is a PTFE pipe, and the interlayer is filled with insulation material and wrapped with a self-regulating heating tape to maintain the temperature fluctuation of the alloy within ±1℃ during transportation. The vacuum generation unit 200 is connected to the filling chamber (located inside the filling control unit 300) via a vacuum pipeline. Various sensors of the quality monitoring unit 400 are arranged at key locations in the filling chamber and on the pipeline. The air inlet of the exhaust gas treatment unit 500 is connected to the exhaust outlet of the filling chamber. The central control system 600 is connected to the sensors and actuators of each unit via signal lines to achieve centralized control and data acquisition.

[0074] Basic Workflow Reference Figure 5 : Step S101, System Preparation and Alloy Pretreatment: The central control system 600 is powered on and performs a self-test. Under the protection of an inert gas (such as high-purity argon, purity >99.999%), the alloy preparation unit 100 adds the raw materials weighed according to precise proportions (e.g., Ga: 83.80-83.99%, In: 12.20%, Sn: 3.60%, possibly containing trace amounts of Zn: 0.20%, Al: 0.01-0.20%) to the reactor, heats it to 30-50℃ to completely liquefy it, and removes oxide particles by stirring (200 rpm, 30 min) and filtering through a sintered metal filter with a pore size of 5 μm. Then, it is transferred to an insulated storage tank for later use, with the storage tank temperature set at 35±0.5℃.

[0075] Step S102, workpiece clamping and sealing: The pressure sensor head to be filled is installed on the special fixture of the filling control unit 300. The automatic alignment system based on machine vision ensures that it is aligned with the capillary of the modular filling head. Then, the pneumatic sealing mechanism is activated to seal the filling chamber. The sealing ring is made of perfluoroether rubber, which has good chemical resistance and high and low temperature performance.

[0076] Step S103, System vacuuming and leakage detection: Start the multi-stage vacuum pump of the vacuum generation unit 200 to evacuate the filling chamber and the inside of the sensor to a vacuum level of 350 mmHg, maintain the pressure for a period of time (e.g., 60 seconds), and confirm that the pressure rise rate is less than 1 mmHg / min (leakage rate meets the standard).

[0077] Step S104, Alloy Filling and Parameter Adjustment: Under negative pressure, liquid gallium indium tin alloy is drawn into the sensor's internal cavity through a capillary. The ultrasonic detector of the quality monitoring unit 400 monitors the alloy flow front in real time. The central control system 600 dynamically adjusts the vacuum level (e.g., from an initial 350 mmHg to 280 mmHg at the end of filling based on the flow decay curve) and, if necessary, adjusts the alloy temperature to ensure smooth, turbulent-free filling. During this process, the flow monitoring system records the filling flow rate in real time and compares it with a preset ideal flow curve. Any significant deviation triggers the intervention of the adaptive algorithm.

[0078] Step S105, Sealing and Curing of the Filling Port: After filling, the filling port is instantly sealed using a fiber-optic-guided Nd:YAG pulsed laser integrated into the filling control unit 300. Laser parameters: power 25W, pulse width 3ms, spot diameter 80μm. Subsequently, the control system slowly fills the chamber with inert gas to atmospheric pressure, with a pressure recovery rate set at 30kPa / min. A local Peltier cooling module can be activated as needed to promote alloy solidification.

[0079] Step S106, Post-processing and cleaning: Open the chamber, remove the filled sensor, and clean the surface with a special alcohol-free electronic cleaner. Perform automatic high-pressure inert gas purging cleaning on the filling head and related contact parts.

[0080] Step S107, Quality Inspection and Data Recording: Perform micro-focus X-ray non-destructive testing on the filled sensor to check the density and uniformity of the filling; conduct electrical performance tests (such as insulation resistance and zero-point output). All process parameters (vacuum degree, temperature, flow rate, time) and test results are automatically recorded and stored, and a unique quality report for the workpiece is generated.

[0081] Step S108, System Maintenance and Preparation: After performing routine checks (such as confirming the filter status and lubricating moving parts) and maintenance, the system is reset and prepared for the next filling.

[0082] Example 2: Detailed Implementation of the Alloy Preparation Unit Reference Figure 2 The alloy preparation unit 100 includes an inert gas protected reactor 110, a storage tank 120, and related auxiliary systems.

[0083] The reactor 110 is made of 316L stainless steel, with an inner wall that may be coated with Teflon or electropolished. Internally, it houses a heating and temperature control system consisting of a wrapped ceramic heater 111 and an armored K-type thermocouple 112, achieving a temperature control accuracy of ±0.3℃. The stirring mechanism 113 is magnetically driven, with a maximum speed of 600 rpm to prevent contamination and leaks. The composition monitor 114 is an online conductivity meter, capable of monitoring the conductivity of the alloy online and indirectly determining compositional uniformity. Inert gas is introduced through the inlet 115, and a slight positive pressure (0.1-0.3 MPa) is maintained internally by a mass flow controller (MFC). A safety relief valve and an observation window (optional) are located on the top of the reactor.

[0084] The prepared alloy is transferred to storage tank 120 via a bottom pneumatic bellows valve. Storage tank 120 also features a stainless steel double-layer vacuum insulation structure 121, with a vacuum level of <0.1 Pa. The inner wall is coated with an anti-adhesion coating (such as a diamond-like carbon film deposited by magnetron sputtering, approximately 2 μm thick). The tank is equipped with a magnetostrictive level gauge 122, a Pt100 platinum resistance temperature sensor 123, and a surrounding heating / cooling coil 124. A PID temperature controller maintains the alloy stably within the desired liquid temperature range (e.g., 35 ± 0.5 °C). A slow-speed magnetic stirrer 125 installed at the bottom can be intermittently activated to prevent component segregation. The storage tank outlet pipeline is also insulated and heated.

[0085] Example 3: Vacuum Generation Unit and Control Strategy Reference Figure 3 The vacuum generation unit 200 employs a multi-stage pump system. The primary pump 210 is a 15 m³ / h oil rotary vane pump used for rough pumping from atmospheric pressure. Once the primary vacuum reaches approximately 10 mmHg, the advanced pump 220 (such as a 55 L / s turbomolecular pump) is activated to raise the vacuum level to a higher level. A vacuum buffer tank 230 (with a volume that can be designed to be 20L depending on the system size) is connected between the pump assembly and the filling chamber to stabilize the system pressure and absorb pulsations caused by pump operation. A dust filter 240 (with a filtration accuracy of 0.1 μm) is installed before the buffer tank to protect the vacuum pump from particulate contamination.

[0086] A digital pressure sensor 250 (using a combination of a capacitive diaphragm gauge (range 0.1-1000 Torr) and a Pirani gauge (range 1×10⁻³-1000 Torr)) monitors the pressure in the filling chamber in real time. The measurement signal is sent to the PLC control system 260, which outputs control signals according to a preset program. By adjusting the opening of the electric throttle valve connected between the buffer tank and the pump (or adjusting the bypass air filling valve), the required negative pressure environment is precisely maintained.

[0087] An example of an adaptive negative pressure control strategy is as follows: Phase 1 (rapid filling, lasting approximately 20% of the total time): Target vacuum of 400 mmHg, rapidly introducing the alloy into the main channel of the workpiece.

[0088] Phase 2 (Stable filling, lasting approximately 60% of the total time): Target vacuum level of 300-350 mmHg, ensuring smooth and continuous flow of the alloy to fill the main cavity.

[0089] Phase 3 (Fine Control / Overfill Prevention, lasting approximately 20% of the total time): Target vacuum of 200-250 mmHg, slow down the flow rate to ensure just filling without overflow, achieving precise control of the liquid level.

[0090] Phase 4 (pulse mode, for complex structures): The pressure fluctuates periodically between 200 mmHg (low pressure duration 1s) and 400 mmHg (high pressure duration 2s), using the "micro-pump" effect generated by the pressure fluctuation to help the alloy overcome microscopic resistance and fill tiny pores and dead zones.

[0091] Example 4: Detailed Implementation of the Filling Control Unit Reference Figure 4 The filling control unit 300 mainly includes a filling head assembly 310, a flow control system 320, and a pressure regulating system 330.

[0092] The filling head assembly 310 features a modular design, allowing for quick replacement based on the workpiece interface type (e.g., threaded, flanged, capillary plug connection), and connects via ISO-KF or similar quick-change flanges. Its core components are a miniature precision valve 311 (e.g., a piezoelectrically driven high-speed switching valve with a response time <5ms) and an extremely fine (preferably 0.25mm) capillary filling tube 312. The capillary material can be 316L stainless steel with an inner wall electropolished to Ra <0.1μm, or a surface treated with plasma-enhanced chemical vapor deposition (PECVD) titanium nitride coating to improve anti-wetting and anti-clogging properties.

[0093] The flow control system 320 includes a Coriolis mass flow meter 321 (range 0-20 g / min, accuracy ±0.5% of reading) and a multi-stage PID controller 322, which can accurately measure and control flow rates as low as 0.1 mL / min.

[0094] In addition to coordinating with the vacuum unit 200 to control the negative pressure in the chamber, the pressure regulation system 330 can also apply a small positive pressure (0-50 kPa adjustable inert gas) to the alloy storage tank as needed to assist filling (positive and negative pressure combination method). All actions are coordinated by the unit controller 340 (based on an embedded PLC) and monitored by the central control system 600. The unit controller 340 has multiple pre-stored filling modes (such as constant pressure filling, constant flow filling, and programmed pressure filling) for selection.

[0095] Example 5: Integrated Application of Quality Monitoring Unit Reference Figure 6 The quality monitoring unit 400 integrates a variety of sensors.

[0096] The visual inspection subsystem 410 includes a 5-megapixel CMOS high-speed industrial camera (120fps) and a high-brightness blue LED coaxial light source, aligned with the sapphire glass observation window of the filling chamber to capture in real time the alloy liquid level, flow state, and the presence of obvious oxide films or large bubbles (diameter >100μm). The image processing algorithm can calculate the liquid level height in real time and identify abnormal reflections in specific areas (which may be due to oxidation).

[0097] The ultrasonic testing subsystem 420 uses a 5MHz center frequency piezoelectric ultrasonic probe coupled to the wall of the filling chamber or the workpiece fixture. By emitting and receiving ultrasonic signals, it can non-invasively monitor the position and velocity of the flow front of the alloy inside the workpiece and detect tiny bubbles (theoretically, bubbles with a diameter >30μm can be detected). The filling state is determined by analyzing the attenuation and time-of-flight changes of the ultrasonic echo.

[0098] Pressure / temperature sensors 430 are distributed throughout key parts of the system, such as filling chambers, vacuum lines, and alloy lines. The pressure sensor accuracy is 0.1%FS, and the temperature sensor accuracy is ±0.1℃.

[0099] All sensor data is fed into the data processing module of the central control system 600 via distributed I / O modules and industrial Ethernet. Built-in adaptive algorithms (such as those using a fuzzy PID controller with a rule base built on extensive process test data) analyze this real-time data and compare it with preset process windows. If deviations are detected (e.g., slow flow rate indicating potential blockage or oxidation), relevant parameters are automatically adjusted (e.g., slightly increasing vacuum or alloy temperature). The online defect detection module performs pattern recognition based on feature extraction and threshold judgment on the acquired images and ultrasonic signals, automatically marking defects such as incomplete filling, excessive bubbles, and severe oxidation, triggering audible and visual alarms or process termination. All detection data and images are stored and bound to the workpiece ID.

[0100] Example 6: Architecture of Exhaust Gas Treatment Unit and Control System Reference Figure 7The exhaust gas treatment unit 500 is mainly used to treat gases emitted during vacuuming and venting processes, which may contain trace amounts of alloy vapors or volatile organic compounds. The exhaust gas first passes through a condenser 510 cooled by three-stage Peltier semiconductor refrigeration chips, with a cold end temperature reaching -15°C, condensing and recovering most of the evaporated alloy components. Then, the gas enters an adsorption tank 520 filled with 20 kg of impregnated activated carbon, adsorbing residual organic matter and extremely fine metal particles. The treated clean gas is discharged through the exhaust port 530. The unit is equipped with a differential pressure sensor to monitor the filter status; when the pressure difference across the adsorption tank exceeds 5 kPa, the system prompts for activated carbon replacement.

[0101] Reference Figure 8 The central control system 600 adopts a distributed control architecture. Its core is the Siemens S7-1500 series industrial PLC 610, responsible for logic control, sequential control, and PID regulation. A 15-inch color touchscreen HMI 620 provides a human-machine interface for parameter setting, process flow display, real-time data curve display, and alarm management. An industrial computer 630 stores all historical data for quality traceability and statistical analysis, using SQL Server as its database. The PLC communicates with the sub-controllers of each unit (such as the vacuum unit PLC 260 and the filling unit controller 340) and the distributed I / O module 640 via Profinet industrial Ethernet, enabling precise control of sensors and actuators throughout the system. The system supports the OPC UA protocol, allowing data exchange with factory-level MES systems.

[0102] Example 7: Pressure Sensor Filling Application Taking the filling of a certain type of high-temperature melt pressure sensor as an example, the specific parameters are shown in the table below:

[0103] After applying this system for filling, the sensor outperforms traditional mercury-filled products in terms of accuracy (up to 0.1%FS), temperature cycling stability (-20℃ to 150℃), and long-term drift performance, and is completely non-toxic. Statistical data shows that after adopting this system, the batch pass rate of this sensor model increased from approximately 92% with traditional processes to over 99.5%.

[0104] Example 8: Application of filling in a mercury-free medical sphygmomanometer Take the filling of the pressure sensing unit (Bourdon tube) of a medical mercury-free sphygmomanometer as an example.

[0105] Workpiece: Spiral Bourdon tube of a mercury-free medical sphygmomanometer (phosphor bronze material, total internal flow channel length approximately 1.2m, equivalent volume approximately 1.5mL).

[0106] Alloy: Standard Ga62.5In21.5Sn16 eutectic alloy (melting point approximately 10.5℃).

[0107] Key processes: The alloy is preheated to 28°C to reduce viscosity. Filling is performed under a constant negative pressure of 280 mmHg to avoid adverse vibrations that pulsed pressure may cause to the flexible Bourdon tube. A vision system is used to monitor the liquid level at the filling port to ensure proper initial filling. Ultrasonic testing is used to monitor the flow continuity of the alloy in long, curved channels to prevent flow interruptions due to oxide film buildup.

[0108] Post-processing and calibration: After filling, it undergoes rigorous aging treatment (temperature cycling) and pressure calibration to ensure that its accuracy reaches ±1 mmHg within the pressure range required by medical standards of 0-300 mmHg.

[0109] The blood pressure monitor sensor unit filled in this system overcomes the pointer fluctuations and inaccurate measurements caused by air bubbles and uneven filling in traditional processes, providing a safe, accurate, and stable mercury-free solution. Testing shows that the hysteresis error of the filled Bourdon tube is less than 0.5%FS, and the repeatability error is less than 0.3%FS.

[0110] Example 9: Application of MEMS micro accelerometer reference cavity filling Taking the filling of the internal reference vacuum cavity of a certain type of MEMS capacitive accelerometer as an example, this demonstrates the system's ability to fill with extremely high precision and extremely small volume.

[0111] Workpiece: Silicon-based MEMS chip, with an internal reference cavity that is a cylindrical cavity with a diameter of 2 mm and a height of 50 μm, and a volume of approximately 0.157 μL (157 nL). The cavity is connected to the outside world through micron-level vent holes.

[0112] Alloy: High-purity Ga68.5In21.5Sn10 eutectic alloy. The alloy must be absolutely free of oxidation to avoid affecting the movement of the MEMS structure.

[0113] Special challenges and responses: Extremely small volume: requires extremely precise flow control. A 0.1mm inner diameter coated quartz capillary and Coriolis mass flow meter, combined with a precision piezoelectric valve, achieve nanoliter-level control accuracy.

[0114] To prevent clogging: the micron-sized air vents are easily clogged by oxide particles. The alloy undergoes ultrafiltration using a 0.5μm pore size filter, and the entire process is carried out under the protection of high-purity argon gas.

[0115] Complete filling and venting: The cavity is tiny, and residual gas has a significant impact. The "high-order pulse negative pressure" mode is adopted: first, the cavity is evacuated to a high vacuum (<0.1 mmHg), and then high-frequency (5Hz) small-amplitude (between 300-350 mmHg) pulse negative pressure is used for filling, and the pressure fluctuation is used to help expel the last gas in the cavity.

[0116] Sealing: After filling, the micron-sized air vents are sealed using focused ion beam (FIB) deposition or local laser remelting technology.

[0117] Quality inspection: The resonant frequency and Q value of the MEMS beam are measured by non-contact laser interferometry to indirectly evaluate the vacuum level inside the cavity (i.e., whether the gas is completely discharged after the alloy is filled).

[0118] Results: After applying this system, complete, oxidation-free, and bubble-free filling of the MEMS reference cavity was successfully achieved, and the final vacuum level inside the cavity was better than 0.1 Pa, which met the design requirements of high-precision MEMS accelerometers.

[0119] In summary, this invention provides a complete, efficient, and reliable solution for negative pressure vacuum filling of gallium indium tin alloys. Its advanced technology and systematic approach fill a gap in this field both domestically and internationally, and it has promising prospects for industrialization.

[0120] The implementation principle of this invention is as follows: This invention discloses a negative pressure vacuum filling system and method for gallium indium tin alloys, belonging to the field of precision instrument manufacturing technology. This system fundamentally inhibits alloy oxidation by constructing a fully enclosed, inert gas-protected environmental chain from raw materials to finished products. Through the adoption of a multi-level adjustable vacuum and adaptive negative pressure control strategy, it achieves precise control of the filling driving force, adapting to the needs of different filling stages and workpieces with different structures. By integrating multi-sensor quality monitoring and a central intelligent control system, it achieves real-time perception, decision-making, and optimization of the filling process, ensuring the consistency and traceability of filling quality. Modular design and compatibility with multiple filling methods endow the system with high flexibility and adaptability. This system effectively solves the toxic pollution problem of traditional mercury filling and systematically overcomes the filling challenges of high viscosity and easy oxidation of gallium indium tin alloys. It is mainly used in the mercury-free manufacturing of precision instruments such as pressure sensors, medical devices, and MEMS devices, and has outstanding advantages such as high precision, high consistency, high safety, environmental friendliness, and strong adaptability.

[0121] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A gallium indium tin alloy negative pressure vacuum filling system, characterized in that, include: An alloy preparation unit (100) is used to prepare and store liquid gallium indium tin alloy under an inert gas protective environment; A vacuum generation unit (200) is used to provide and maintain a stable negative pressure environment for the filling chamber; A filling control unit (300) is used to precisely fill the liquid gallium indium tin alloy into the workpiece under the negative pressure environment; The quality monitoring unit (400) is used to monitor the filling process and quality in real time and provide feedback to control the filling parameters; The exhaust gas treatment unit (500) is used to treat the exhaust gas generated during the filling process; The central control system (600) is communicatively connected to the alloy preparation unit (100), vacuum generation unit (200), filling control unit (300), quality monitoring unit (400) and waste gas treatment unit (500) to control the coordinated operation of each unit.

2. The gallium indium tin alloy negative pressure vacuum filling system according to claim 1, characterized in that, The alloy preparation unit (100) includes: An inert gas protected reactor (110) is equipped with a heating system (111), a stirring mechanism (112), and a component monitoring instrument (113). An alloy storage tank (120) with a double-layer insulation structure and an anti-sticking coating inner wall. The alloy storage tank (120) is connected to a temperature control system to maintain the gallium indium tin alloy in a liquid temperature range between -32°C and 200°C.

3. The gallium indium tin alloy negative pressure vacuum filling system according to claim 1, characterized in that, The vacuum generation unit (200) includes: A multistage vacuum pump system, comprising a primary rotary vane pump (210) and an advanced molecular pump (220). A vacuum buffer tank (230) is connected between the multi-stage vacuum pump system and the filling chamber. Dust filtration device (240) is installed at the front end of the vacuum buffer tank (230). A digital pressure sensor (250) for real-time monitoring of the vacuum level of the filling chamber; In addition, a PLC-based vacuum controller is used to adaptively adjust the vacuum level of the filling chamber within the range of 200-400 mmHg based on the feedback signal from the digital pressure sensor (250) and a preset program.

4. The gallium indium tin alloy negative pressure vacuum filling system according to claim 3, characterized in that, The PLC-based vacuum controller is configured to execute an adaptive negative pressure control strategy, which includes: A higher vacuum level is used during the initial filling stage; A second, lower vacuum level is used when the alloy is nearly filled into the workpiece; And / or, for workpieces with complex microstructures, a periodically alternating pulsed negative pressure is used within the range of 200-400 mmHg.

5. A gallium indium tin alloy negative pressure vacuum filling system according to claim 1, characterized in that, The filling control unit (300) includes: Modular filling head (310) is equipped with a miniature precision valve and a capillary filling tube with an inner diameter of 0.1-0.5 mm; A high-precision flow monitoring and control system (320) is used to monitor and control the filling flow rate in the range of 0.1-10 mL / min; The filling control unit (300) can fill the container using a negative pressure method, a positive pressure method, or a combination of positive and negative pressure methods.

6. The gallium indium tin alloy negative pressure vacuum filling system according to claim 1, characterized in that, The quality monitoring unit (400) employs multi-sensor fusion technology, including: A visual inspection subsystem (410) is used to detect air bubbles and oxidation during the filling process; An ultrasonic testing subsystem (420) is used for non-invasive monitoring of the flow state of alloys inside a workpiece; Pressure and temperature sensors (430) are used to monitor filling environment parameters; The central control system (600) receives data from the multiple sensors and dynamically adjusts the filling parameters through a built-in adaptive algorithm, and has online defect detection and alarm functions.

7. The gallium indium tin alloy negative pressure vacuum filling system according to claim 1, characterized in that, The waste gas treatment unit (500) includes a condensation recovery device (510) and an activated carbon adsorption device (520) connected in sequence, for removing alloy vapors and volatile organic compounds from the waste gas.

8. A gallium indium tin alloy negative pressure vacuum filling system according to any one of claims 1 to 7, characterized in that, The central control system (600) includes a programmable logic controller (PLC) (610), a human-machine interface (HMI) (620), and a data recording module, which are used to realize automated system operation, process parameter setting, real-time status monitoring, and production data traceability.

9. A method for negative pressure vacuum filling of gallium indium tin alloy using the system described in any one of claims 1-8, characterized in that, Includes the following steps: System preparation and alloy pretreatment steps (S101): Under inert gas protection, the gallium indium tin alloy is heated to liquid state and filtered; Workpiece clamping and sealing step (S102): Install the workpiece into the filling station and seal it to form a filling chamber; System vacuuming and leakage detection steps (S103): Vacuum the filling chamber and the inside of the workpiece to a preset negative pressure and perform leakage detection; Alloy filling and parameter adjustment steps (S104): Liquid gallium indium tin alloy is filled into the workpiece under negative pressure difference, and the filling parameters are dynamically adjusted according to the quality monitoring signal; Filler port sealing and curing step (S105): Seal the filler port of the workpiece and restore the chamber to normal pressure; Post-processing and quality inspection steps (S106): Clean the workpiece and inspect and record the filling quality.

10. The method according to claim 9, characterized in that, In the alloy filling and parameter adjustment step (S104), the filling vacuum degree is dynamically adjusted between 200 mmHg and 400 mmHg according to the filling process, and / or a pulsed negative pressure that alternates periodically between 200 mmHg and 400 mmHg is used for filling.

Images