In-situ self-forming method of liquid metal heat conduction interface in micro base station assembly

Abstract

The invention relates to an in-situ self-forming method of a liquid metal heat conduction interface in micro base station assembly, and belongs to the technical field of microelectronic device assembly and heat management. The method aims at solving the technical problems that the wettability of liquid metal on a micro base station substrate is poor, so that a heat conduction interface is not uniform, the liquid metal is prone to oxidation, and the heat conduction performance and stability are affected. According to the technical scheme, the method comprises the steps of performing plasma treatment on a substrate to increase surface energy; placing the processed substrate in a sealed cavity, and introducing inert gas to form a low-oxygen environment; liquid metal is deposited to an effective area of a substrate through a micro-droplet jetting device, ultrasonic vibration is synchronously applied in the whole deposition process, and the liquid metal is promoted to spread and surface oxides are removed through the shearing force and the cavitation effect of the ultrasonic vibration; and finally, the substrate is heated and cured, so that the liquid metal is converted into a solid state, and a stable heat-conducting interface is formed. The method is mainly used for constructing an efficient and reliable heat conduction interface in compact electronic equipment such as a micro base station.

Description

Technical Field

[0001] This invention belongs to the field of microelectronic device assembly and thermal management technology, specifically relating to an in-situ self-formation method of liquid metal thermal interface in micro base station assembly. Background Technology

[0002] In the assembly of compact electronic devices such as micro base stations, the formation of efficient thermally conductive interfaces is crucial for ensuring heat dissipation of critical heat-generating components. Liquid metal, with its high thermal conductivity, is considered a potentially ideal material for constructing such interfaces. However, the direct use of liquid metal in practical applications faces challenges. On the one hand, common substrate materials have low surface energy, resulting in poor wettability of liquid metal on their surfaces. This makes it difficult for liquid metal to spontaneously spread and form a uniform, continuous thin layer, easily leading to areas of incomplete coverage or uneven thickness, thus affecting the overall uniformity and efficiency of heat conduction at the interface. On the other hand, liquid metal is chemically reactive and readily oxidizes in ambient atmospheres. The oxides formed on its surface significantly increase the interfacial contact thermal resistance and may cause interface performance degradation over time, affecting long-term operational stability. To address the wettability issue, surface treatment of the substrate was attempted to improve its surface energy. However, the highly active surface after treatment is prone to failure due to exposure in subsequent process steps. To prevent oxidation, the process is usually carried out under inert gas protection. However, how to continuously and effectively isolate oxygen and maintain the ideal state of the substrate surface during the process from treatment to liquid metal deposition, while promoting the controllable and uniform spread of high-viscosity liquid metal in a microscale area, has always been a challenge in the process implementation. Summary of the Invention

[0003] One object of the present invention is to solve at least the above-mentioned problems and to provide at least the advantages that will be described later.

[0004] Another objective of this invention is to provide an in-situ self-formation method for a liquid metal thermal interface in micro base station assembly, which can effectively improve the wettability and spreading uniformity of liquid metal on the substrate, inhibit the oxidation of liquid metal, and ultimately form a dense and stable thermal interface.

[0005] To achieve these objectives and other advantages of the present invention, an in-situ self-formation method for a liquid metal thermal interface in micro base station assembly is provided, comprising the following steps: S1: Perform plasma treatment on the substrate of the micro base station. The plasma treatment power is 100-500 W and the treatment time is 30-300 seconds to increase the surface energy of the substrate. S2: Place the plasma-treated substrate into a sealed cavity, and introduce inert gas into the sealed cavity to reduce the oxygen concentration in the sealed cavity to below 100 ppm, thus forming an inert gas environment. S3: Liquid metal is deposited onto the effective area of ​​the substrate where a thermally conductive interface needs to be formed using a microdroplet jetting device. The nozzle diameter of the microdroplet jetting device ranges from 10 to 100 μm, the liquid metal deposition rate is 0.01 to 0.1 μL / s, and the deposited liquid metal covers 80% to 95% of the effective area surface area. In this process, while depositing liquid metal, ultrasonic vibration is applied to the substrate. The frequency of the ultrasonic vibration is 20-100kHz and the amplitude is 1-10μm. The application time of the ultrasonic vibration covers the entire process of liquid metal deposition. The shear force and cavitation effect generated by the vibration are used to promote the spread of liquid metal and remove its surface oxides. S4: After the liquid metal deposition and accompanying ultrasonic vibration steps are completed, the substrate is heated and cured at a temperature of 50-100 ℃ for 1-10 minutes to transform the liquid metal from a liquid to a solid state, thereby forming a stable thermally conductive interface.

[0006] In micro base station assembly, liquid metal often struggles to form a uniform thermally conductive interface due to its poor wettability on the substrate surface. Furthermore, its susceptibility to oxidation impairs the interface's thermal conductivity and long-term stability. To address this, plasma treatment is first used to increase the substrate surface energy, enhancing the liquid metal's spreading ability. Subsequently, operation is performed in an inert gas environment to effectively reduce oxygen concentration and prevent oxidation of the liquid metal during deposition. Simultaneously with the liquid metal deposition via microdroplet jetting, ultrasonic vibration is applied. The shear force and cavitation effect generated by the vibration promote the flow and spreading of the liquid metal and remove any existing surface oxides. Finally, heating and solidification transform the liquid metal into a solid state, resulting in a dense and firmly bonded thermally conductive interface. This synergistic effect not only improves the uniformity of liquid metal coverage in the microscale region but also significantly suppresses interface oxidation, resulting in a thermally conductive interface with low thermal resistance and good reliability.

[0007] Preferably, the plasma treatment step of the micro base station substrate is performed within a sealed cavity, specifically including: Before introducing inert gas into the sealed cavity, a mixed gas is first introduced into the sealed cavity as a plasma treatment atmosphere. The mixed gas consists of an inert gas and a silicon-containing organic gas, wherein the inert gas is argon and the silicon-containing organic gas is hexamethyldisilazane, and the volume flow ratio of argon to hexamethyldisilazane is 95:5-85:15. Plasma treatment is carried out in a mixed atmosphere, with a power of 100-500 W and a treatment time of 30-300 seconds. After the plasma treatment is completed, the plasma power supply is turned off, the mixed gas continues to flow, and the substrate temperature is controlled at 50-80 ℃ for 30-120 seconds to allow hexamethyldisilazane to thermally decompose on the substrate surface to form a siloxane passivation layer with a thickness of 1-10 nm and a surface coverage of more than 90%. Stop introducing the mixed gas and introduce pure inert gas into the sealed cavity to replace the residual gas, so that the oxygen concentration in the sealed cavity drops below 100 ppm.

[0008] After plasma treatment enhances the surface energy of the substrate, the newly activated surface is prone to a rapid decrease in surface energy due to contact with the ambient atmosphere during transfer or while awaiting subsequent deposition steps, thus affecting the final wettability of the liquid metal. To address this, immediately after plasma treatment, a silicon-containing organic gas is introduced into the cavity, causing thermal decomposition on the substrate surface to form an extremely thin siloxane protective layer. This protective layer effectively isolates the substrate from the environment, maintaining its highly active state after treatment. During subsequent liquid metal deposition, the accompanying ultrasonic vibration and heating curing process effectively removes this temporary protective layer, exposing a fresh substrate surface with high surface energy. This method allows the substrate to maintain optimal wetting conditions at the moment of contact with the liquid metal, improving process controllability and repeatability.

[0009] Preferably, in the step of depositing liquid metal onto the substrate using a microdroplet ejection device, a DC electric field is applied between the nozzle of the microdroplet ejection device and the substrate. The DC electric field is applied by connecting the substrate to the positive terminal of the DC power supply and connecting the nozzle of the microdroplet ejection device to the negative terminal of the DC power supply. The electric field strength of a DC electric field is 0.5-5 kV / mm; The DC electric field is applied for a period of time covering the entire liquid metal deposition process, and the application of the DC electric field is carried out simultaneously with the application of ultrasonic vibration.

[0010] In the process of depositing liquid metal via microdroplet jetting, tiny metal droplets are easily disturbed by ambient airflow or mechanical vibrations of the equipment, causing their flight paths to deviate and the deposition location to deviate from the preset area. This results in decreased accuracy of the thermal interface pattern and uncontrolled coverage. To address this, a stable DC electric field is applied between the nozzle and the substrate. Utilizing the excellent conductivity of the liquid metal itself, the jetted droplets acquire a charge during flight and, guided by the continuous electric field, fly along a preset path to the target area on the substrate. This measure significantly enhances the directionality and stability of the droplet movement, enabling it to overcome external disturbances and accurately reach the designated position. This ensures that the shape, size, and position of the deposited pattern highly match the design requirements, improving the accuracy and consistency of the interface preparation.

[0011] Preferably, the DC electric field is applied in the form of a pulsed DC electric field; The pulse frequency of the pulsed DC electric field is the same as the frequency of the ultrasonic vibration, and the pulse frequency range is 20-100kHz. The pulse width of the pulsed DC electric field accounts for 20%-80% of a single pulse period; The pulse start time of the pulsed DC electric field is synchronized with the vibration signal of the ultrasonic vibration through a phase-locked circuit, with a synchronization error of less than 10 microseconds, so that the pulse start time of the pulsed DC electric field corresponds to the moment when the ultrasonic vibration displacement at the center point of the deposition area on the substrate surface reaches the positive maximum value.

[0012] During liquid metal deposition, if a DC electric field and ultrasonic vibration act simultaneously and continuously, the electromagnetic-acoustic coupling may cause irregular flow of the liquid metal, leading to stripes or island-like defects at the interface. To address this, the DC electric field is converted into a pulsed form, with its pulse frequency matching the ultrasonic vibration frequency. A phase-locked circuit precisely controls the pulse start time, ensuring synchronization with the moment when the ultrasonic vibration displacement on the substrate surface reaches its maximum value. This confines the electric field effect to the stable, compressed phase of the vibration waveform, preventing interference with the liquid metal spread in the rarefied phase. This suppresses flow instability and defect formation, contributing to a more uniform and complete deposition interface.

[0013] Preferably, the phase-locked circuit includes a vibration signal sensor, a signal conditioning module, a phase comparator, an adjustable delay unit, a voltage pulse detector, and a pulse generator; The vibration signal sensor is a piezoelectric accelerometer, which is attached to the surface of the transducer that applies ultrasonic vibration or to the vibration transmission component that is in direct contact with the substrate, and is used to collect the vibration signal of ultrasonic vibration in real time. The signal conditioning module is connected to the vibration signal sensor and is used to filter and amplify the collected vibration signal. The center frequency of the filtering band is the set frequency of the ultrasonic vibration, and the bandwidth is 10% of the set frequency, so as to extract a pure vibration reference signal. The first input terminal of the phase comparator is connected to the output terminal of the signal conditioning module to receive the vibration reference signal, and the second input terminal is connected to the feedback signal. The voltage pulse detector is used to acquire the pulse voltage signal actually applied between the substrate and the nozzle in real time, and sends the pulse voltage signal as a feedback signal to the second input terminal of the phase comparator. The input terminal of the adjustable delay unit is connected to the output terminal of the pulse generator, and the output terminal of the adjustable delay unit generates the control pulse signal for the final applied pulsed DC electric field. The phase comparator compares the phase of the vibration reference signal with the feedback signal and outputs an error voltage signal that is proportional to the phase difference between the two. The adjustable delay device dynamically adjusts its delay time according to the error voltage signal, with an adjustment range of 0-25 microseconds and an adjustment accuracy of 0.1 microseconds, so that the phase of the actual pulse voltage signal continuously tracks the phase of the vibration reference signal, thereby locking the pulse start time of the control pulse signal at the phase when the vibration reference signal reaches its positive maximum value.

[0014] During prolonged liquid metal deposition, the ultrasonic transducers in the equipment may experience slight frequency or phase drift in their vibration signals due to temperature rise or changes in mechanical load. This causes the pre-set, fixed-phase electric field pulses to gradually lose precise synchronization with the actual mechanical vibration waveform, thus affecting the synergistic effect of both. To address this, a closed-loop phase-locking system was designed. This system acquires the actual vibration signal and the applied pulse voltage signal in real time, dynamically detects the deviation between the two through phase comparison, and uses an adjustable delay unit to adjust the timing of the electric field pulses in real time. This mechanism can automatically track and compensate for changes in the vibration signal, ensuring that each electric field pulse is applied precisely at the stable compressed phase of the vibration waveform. This maintains a stable and reliable synchronization between the electric field and vibration even under fluctuating process conditions, guaranteeing the uniformity and quality consistency of the deposition interface.

[0015] Preferably, before the step of depositing liquid metal onto the substrate using a microdroplet jetting device, a surface dynamic activation step is performed first. The surface dynamic activation step specifically includes: The ultrasonic vibration is activated, and the potential difference between the substrate and the nozzle of the microdroplet ejection device is linearly increased from zero to a preset pretreatment voltage within 1-5 seconds, and maintained for 5-30 seconds after reaching the pretreatment voltage. The electric field strength corresponding to the pretreatment voltage is 0.1 kV / mm to 0.5 kV / mm; the value of the pretreatment voltage increases the charge density on the substrate surface by 10%-50% without causing gas breakdown. After the surface dynamic activation step is completed, the ultrasonic vibration is maintained, and the potential difference between the substrate and the nozzle of the microdroplet jetting device is maintained at the state at the end of the surface dynamic activation step. At the same time, the microdroplet jetting device is turned on to start the deposition of liquid metal.

[0016] Even after plasma treatment and in-situ passivation, the substrate surface may not be in optimal activity at the moment of initial contact with liquid metal droplets, resulting in insufficient spreading of the initially deposited liquid metal and affecting the uniformity of the entire thermal interface in its early stages. Therefore, a dynamic surface activation step is added before the formal liquid metal deposition: simultaneously with ultrasonic vibration, the potential difference between the substrate and the nozzle is slowly and linearly increased from zero to a lower preset value and maintained for a period of time. This gentle and gradually increasing electric field, in synergy with continuous ultrasonic vibration, pre-treats the substrate surface in a non-contact manner. This process helps to further remove residual gas molecules physically adsorbed on the surface and optimizes the distribution of surface charge, thus providing a highly active and clean contact surface at the moment liquid metal deposition begins. This lays a good initial foundation for the subsequent uniform spreading of the liquid metal, contributing to improved uniformity and consistency of the entire interface formation.

[0017] Preferably, in the surface dynamic activation step, the electric field formed by the potential difference applied between the substrate and the nozzle is a rotating electric field; The rotating electric field is generated by two sets of mutually orthogonal electrode pairs, where the voltage applied to the first pair of electrodes is U. x =U0(t)×sin(ωt), the voltage applied to the second pair of electrodes is U y =U0(t)×cos(ωt), where U0(t) is the time-varying voltage amplitude that increases linearly from 0 to the value corresponding to the pre-processed voltage, ω is the angular frequency of the electric field rotation; sin(ωt) and cos(ωt) are functions that change periodically with time t; The electric field rotation angular frequency ω and the ultrasonic vibration frequency f satisfy the following relationship: ω=2π×n×f, where n is an integer and the value range is 1-10; During the surface dynamic activation step, the electric field rotation angular frequency ω remains constant as U0(t) increases linearly and is maintained. The direction of rotation of the rotating electric field remains unchanged.

[0018] In the surface dynamic activation step, due to the potential anisotropy of the microstructure or local differences in composition on the substrate surface, applying an electric field in only one direction will result in directional selectivity, making it difficult to uniformly cover all areas and potentially leaving areas with insufficient activation. Therefore, a rotating electric field is used to apply the pretreatment voltage: two sets of orthogonal electrode pairs apply sinusoidal and cosine voltages with a 90° phase difference, forming a continuously rotating electric field on the substrate plane. This rotating electric field applies uniform perturbation and peeling force to the substrate surface from all azimuth directions, effectively eliminating the activation unevenness caused by a fixed electric field direction. This results in comprehensive optimization of surface adsorbates, residual passivation layers, and charge distribution. Consequently, the substrate surface exhibits an isotropic, highly active state after activation, laying a more consistent foundation for the subsequent uniform deposition of liquid metal.

[0019] Preferably, in the step of heating and curing the substrate, a combination of staged gradient heating and synchronous micro-amplitude mechanical vibration is used, specifically including: After the ultrasonic vibration ends, the first heating stage is started, and the substrate temperature is raised from the ambient temperature to the first target temperature W1 at the first heating rate, and held at this temperature for a first time s1. The first heating rate is 1-5 ℃ / s, the first target temperature W1 is 10-20 ℃ above the solidus temperature of the liquid metal and W1≤60 ℃, and the first time s1 is 10-60 seconds. During the first heating stage, while maintaining the temperature, a first mechanical vibration is applied to the substrate. The frequency f1 of the first mechanical vibration is 1-5 kHz, the amplitude A1 is 0.1-1 μm, and the vibration direction is perpendicular to the substrate surface. After the first heating stage is completed, the second heating stage begins, and the substrate temperature is raised from W1 to the final curing temperature W2 at a second heating rate. The curing temperature W2 is 50-100 °C. The second heating rate is lower than the first heating rate, at 0.2-1 ℃ / s; During the second heating process and the initial heat preservation stage after reaching W2, a second mechanical vibration is applied to the substrate. The frequency f2 of the second mechanical vibration is 50-200 Hz, the amplitude A2 is 2-10 μm, and the vibration direction is parallel to the substrate surface. The second mechanical vibration is applied in an intermittent pulse mode, specifically: vibration duration τ on The interval between 2 and 10 seconds is the intermittent stillness time τ. off It lasts 5-20 seconds, and τ on <τ off ; The curing progress is determined by real-time monitoring of substrate temperature or curing process characteristic signals, and the timing of switching between vibration cessation and temperature maintenance is controlled accordingly. Specifically: Once the substrate temperature reaches W2, timing begins, and the physical signal reflecting the solidification state of the liquid metal is continuously monitored. This physical signal is the rate of change V of the liquid metal layer surface height, measured by a laser displacement sensor. h ; When V is detected h Drops below the preset threshold V th When the solidification of the liquid metal body is determined to be complete, the second mechanical vibration is stopped; V th The value is 0.01-0.1 μm / s, and V th The value of is directly proportional to the viscosity of the liquid metal and the curing shrinkage rate; After the vibration stops, maintain the substrate temperature at W2 and continue to heat it until the total heating time reaches the preset value, thus completing the final solidification of the liquid metal.

[0020] During the heating and curing stage of the liquid metal thermal interface, a single heating process can easily lead to microscopic thermal stress concentration and microcracks within the interface due to uneven internal heat transfer and asynchronous shrinkage during solidification phase transformation. Simultaneously, voids may form at the solid-liquid interface due to volume shrinkage, compromising the interface's mechanical integrity and long-term thermal conductivity stability. To address this, a combination of staged gradient heating and synchronous mechanical vibration is employed: First, the temperature is rapidly increased to slightly above the melting point of the liquid metal and held at this temperature, while simultaneously applying high-frequency, low-amplitude vertical vibration to promote uniform temperature distribution in the liquid metal layer and release pre-process stress, while also helping to remove trapped gases. Subsequently, the temperature is increased at a slower rate to the final curing temperature. During this process and in the initial holding phase, low-frequency, high-amplitude intermittent pulse vibration parallel to the substrate surface is applied. This mechanical disturbance using shear mode breaks up dendrites, promotes compositional homogenization, and compensates for shrinkage deformation. During the vibration intervals, the liquid metal is allowed to backfill any micropores that may have formed under surface tension. By accurately determining the solidification completion point of the main body through real-time monitoring of the rate of change in the surface height of the liquid metal layer, vibration is promptly stopped, and the system is placed in a static, heat-insulating state. This method effectively controls the solidification kinetics, reduces internal stress, and suppresses defect formation, thereby obtaining a dense, uniform, and firmly bonded solid thermally conductive interface.

[0021] The present invention has at least the following beneficial effects: First, this invention effectively improves the spreading ability and coverage uniformity of liquid metal on microscale substrates through the synergistic effect of plasma treatment, microdroplet deposition under inert gas protection and ultrasonic vibration, and final heating and curing. At the same time, it significantly inhibits interface oxidation, resulting in a thermally conductive interface with low thermal resistance and good thermal conductivity stability.

[0022] Secondly, by introducing precise control methods such as electric field guidance, phase synchronization locking, and rotating electric field activation, the present invention achieves more precise control over the deposition trajectory of liquid metal droplets, the instantaneous state of contact with the substrate, and the timing of multi-field coupling effects throughout the entire process. This significantly improves the positional accuracy of the deposition pattern, the initial uniformity of the interface formation, and the consistency and repeatability of the process.

[0023] Third, this invention uses staged gradient heating combined with intelligently controlled mechanical vibration to optimize the solidification dynamics of liquid metal, effectively alleviate the internal stress concentration caused by uneven phase transformation shrinkage, and suppress the generation of defects such as microcracks and voids. The resulting solid thermal interface structure is dense and has good mechanical integrity, with excellent long-term working reliability.

[0024] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Detailed Implementation

[0025] The present invention will now be described in further detail so that those skilled in the art can implement it based on the description.

[0026] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0027] Example 1 A method for in-situ self-formation of a liquid metal thermal interface in micro base station assembly, comprising the following steps: S1: Take a ceramic substrate for a micro base station and treat its surface using a plasma cleaner. Set the plasma treatment power to 200 W and the treatment time to 120 seconds. After treatment, the surface energy of the substrate is significantly increased.

[0028] S2: The plasma-treated substrate is immediately transferred to a sealed process chamber. High-purity argon gas is continuously introduced into the chamber to purge and replace it until the oxygen concentration is stably reduced to below 100 ppm, as monitored by an oxygen content sensor integrated inside the chamber, thus forming a stable inert gas environment.

[0029] S3: In an inert gas environment, a precision microdroplet jetting device is used to deposit gallium indium tin eutectic alloy liquid metal onto a pre-designed effective area (i.e., the location corresponding to the heat-generating chip) on the substrate. The nozzle diameter of the microdroplet jetting device is 50 μm, and the liquid metal deposition rate is set to 0.05 μL / s. The deposition process is controlled so that the final deposited liquid metal covers 90% of the effective area surface area.

[0030] Throughout the liquid metal deposition process, ultrasonic vibrations were simultaneously applied to the stage supporting the substrate. The frequency of the ultrasonic vibrations was set to 60 kHz, and the amplitude was set to 5 μm. The vibrations were generated by a transducer coupled to the stage. The shear force generated by this vibration promoted the spreading and flow of the liquid metal on the substrate surface, while the cavitation effect helped remove the extremely thin oxides that might form on the liquid metal surface.

[0031] S4: After completing the liquid metal deposition and accompanying ultrasonic vibration, the substrate undergoes a heat curing process. The substrate is placed on a heating stage and heated at a constant temperature of 80 ℃ for 5 minutes. During this process, the liquid metal completely transforms from a liquid state to a solid state, forming a tight and stable thermally conductive interface with the substrate.

[0032] Example 2 A method for in-situ self-formation of a liquid metal thermal interface in micro base station assembly, differing from Example 1 in that the plasma treatment step of the micro base station substrate is performed within a sealed cavity, specifically including: The ceramic substrate for the micro base station is placed in a sealed process chamber that can be subjected to plasma treatment.

[0033] First, a mixture of high-purity argon and hexamethyldisilazane (HMDS) is introduced into the sealed cavity. The volumetric flow rate ratio of argon to HMDS is set to 90:10. The total flow rate of the mixed gas is 20 sccm (standard cubic centimeters per minute) to achieve a stable flow state within the cavity.

[0034] Next, under the mixed atmosphere, the plasma generator is activated to perform plasma treatment on the substrate surface. The plasma treatment power is set to 300 W, and the treatment time is 180 seconds. This process significantly increases the surface energy of the substrate.

[0035] Furthermore, after the plasma treatment is completed, the plasma power supply is turned off, but the mixed gas in the aforementioned proportion continues to be introduced into the cavity at the same flow rate. Simultaneously, the substrate temperature is precisely controlled at 65 °C using a heating stage at the bottom of the cavity, and maintained at this condition for 75 seconds. During this period, hexamethyldisilazane undergoes thermal decomposition on the activated surface of the substrate, forming a siloxane passivation layer with a thickness of approximately 5 nm and a surface coverage greater than 90%.

[0036] Finally, the flow of the mixed gas was stopped, and pure argon gas was continuously introduced into the sealed cavity to displace the residual gas. Monitoring continued until the oxygen concentration in the cavity dropped below 100 ppm, creating a pure inert gas environment.

[0037] Example 3 A method for in-situ self-formation of liquid metal thermal interface in micro base station assembly differs from Example 2 in that, based on the substrate obtained in Example 2, which has undergone in-situ passivation and is in an inert gas environment, the liquid metal deposition steps are as follows: 1. Electric Field System Setup: Within the sealed cavity, the substrate is connected to the positive output terminal of a programmable DC power supply via conductive clamps. The metal nozzle (50 μm in diameter) of the microdroplet ejection device is connected to the negative output terminal of the same power supply. The distance between the nozzle and the deposition area on the substrate surface is adjusted to 1 mm, and the output parameters of the DC power supply are set to create a stable DC electric field with an electric field strength of 3 kV / mm between them. Simultaneously, the DC power supply is configured to operate in pulse mode.

[0038] 2. Process parameter setting and synchronous preparation: The ultrasonic vibration frequency was set to 60 kHz and the amplitude to 5 μm.

[0039] The pulse frequency of the pulsed DC electric field is set to be the same as the ultrasonic vibration frequency, which is 60 kHz.

[0040] Set the pulse width to be 50% of a single pulse cycle.

[0041] A phase-locked circuit is configured to ensure that the pulse start time of the pulsed DC electric field is synchronized with the moment when the ultrasonic vibration displacement at the center point of the deposition area on the substrate surface reaches its positive maximum value, with a synchronization error controlled to be less than 10 microseconds. This phase-locked circuit includes a piezoelectric accelerometer (for acquiring vibration signals) attached to the vibration transmission component (workpiece stage) in direct contact with the substrate, a signal conditioning module, a phase comparator, an adjustable delay unit (adjustment range 0-25 microseconds, accuracy 0.1 microseconds), a voltage pulse detector, and a pulse generator. Through pre-experimental calibration, the vibration signal acquired by the sensor is phase-mapped with the vibration displacement at the center point of the deposition area, establishing a signal delay compensation model to ensure that the conditioned vibration reference signal accurately reflects the displacement change at the center point.

[0042] 3. Liquid metal deposition and multi-field synergy: Turn on the ultrasonic vibration generator to apply continuous ultrasonic vibration to the substrate.

[0043] Simultaneously, the pulsed DC electric field power supply and phase-locked circuit are activated. The pulsed DC electric field is applied synchronously with the ultrasonic vibration, covering the entire subsequent liquid metal deposition process. Under the closed-loop control of the phase-locked circuit, the start time of each voltage pulse is precisely locked to the stable compressed phase of the ultrasonic vibration waveform.

[0044] Under the combined effects of the aforementioned vibration and synchronous pulsed electric field, the microdroplet ejection device is activated. Liquid gallium indium tin eutectic metal is ejected and deposited onto the effective area of ​​the substrate at a deposition rate of 0.05 μL / s. Guided by the synchronous pulsed electric field, the charged liquid metal microdroplets precisely fly towards the target area.

[0045] The deposition process was controlled to ensure that the final liquid metal coverage area accounted for 90% of the effective surface area. Throughout the deposition process, ultrasonic vibration promoted the spread and deoxidation of the liquid metal, while a synchronized pulsed electric field ensured the precise deposition of microdroplets and the stability of interfacial flow.

[0046] 4. Heat curing: After deposition is complete, ultrasonic vibration and pulsed electric field are stopped. The substrate is transferred to a heating stage under inert gas protection (or the cavity integrated heating function is used directly), and heated at a constant temperature of 80 ℃ for 5 minutes to completely solidify the liquid metal and form a stable thermally conductive interface.

[0047] Example 4 An in-situ self-formation method for liquid metal thermally conductive interfaces in micro base station assembly is disclosed in this embodiment. Based on Embodiment 3, a surface dynamic activation step is added before the liquid metal deposition step, as detailed below: Before performing the liquid metal deposition and multi-field synergistic effect as described in Example 3, surface dynamic activation is first performed. The specific steps are as follows: 1. Activate ultrasonic vibration: First, start the ultrasonic vibration generator to apply continuous ultrasonic vibration to the substrate in an inert gas environment. Set the vibration frequency to 60 kHz and the amplitude to 5 μm.

[0048] 2. Dynamic activation by applying a rotating electric field: Electrode configuration: In the sealed cavity, two sets of mutually orthogonal electrode pairs (the first pair of electrodes is along the X-axis and the second pair of electrodes is along the Y-axis) are arranged parallel to the substrate plane to apply a rotating electric field between the substrate and the nozzle of the microdroplet ejection device (actually the area above the substrate plane near the nozzle).

[0049] Voltage parameter settings: Set the target pretreatment voltage value so that the corresponding electric field strength is 0.3 kV / mm (this voltage value can increase the charge density on the substrate surface by about 30% without causing gas breakdown). Maintain the vertical distance between the nozzle and the substrate surface as in Example 3 (1 mm). According to the electric field strength formula E=U / d, the pretreatment voltage is calculated as U=E×d=0.3 kV / mm×1mm=0.3 kV. Rotating electric field generation: controlling the voltage applied to two sets of electrodes. The voltage of the first pair of electrodes is U. x= U0(t)×sin(ωt), the voltage of the second pair of electrodes is U y = U0(t)×cos(ωt).

[0050] The voltage amplitude U0(t) starts from 0 and increases linearly to the amplitude corresponding to the preprocessed voltage within 3 seconds, and then maintains the amplitude unchanged for 15 seconds.

[0051] The electric field rotation angular frequency ω is set as ω = 2π × n × f, where the ultrasonic vibration frequency f = 60 kHz, and n = 5. Therefore, ω = 2π × 5 × 60000 rad / s = 600000 π rad / s (angular frequency in radians per second), and remains constant during the linear increase and maintenance of U0(t).

[0052] The direction of rotation remains clockwise.

[0053] Activation process: Under the above parameters, the rotating electric field power supply is turned on. Simultaneously with the ultrasonic vibration, the intensity of the rotating electric field on the plane containing the substrate surface gradually increases from zero and eventually stabilizes, continuously acting on the substrate surface for approximately 18 seconds (3 seconds of boost + 15 seconds of hold). During this process, the rotating electric field and ultrasonic vibration work synergistically to dynamically activate the substrate surface that has already undergone in-situ passivation.

[0054] 3. Direct connection to liquid metal deposition: After the surface dynamic activation step is completed, the output of the rotating electric field power supply is stopped, the application of ultrasonic vibration remains unchanged, and then the system is switched to the pulsed DC electric field system as described in Example 3 (that is, the substrate is connected to the positive terminal of the DC power supply and the nozzle is connected to the negative terminal), and the pulse power supply and phase locking circuit are started.

[0055] Immediately activate the microdroplet ejection device. At this point, liquid metal microdroplets begin to deposit onto the effective area of ​​the dynamically activated substrate under the combined action of ultrasonic vibration and synchronous pulsed DC electric field. The specific parameters and controls of the subsequent deposition process (such as deposition rate, pulsed electric field synchronization, coverage area, etc.) are exactly the same as those described in steps 3 and 4 of Example 3.

[0056] Example 5 An in-situ self-formation method for a liquid metal thermally conductive interface in micro base station assembly is disclosed. In this embodiment, after completing the liquid metal deposition step as described in Example 4, a combination of staged gradient heating and synchronous micro-amplitude mechanical vibration is used when heating and curing the substrate. The specific steps are as follows: A gallium-based liquid metal alloy with a solidus temperature of approximately -10 °C is used for illustration.

[0057] 1. First heating stage: The heating process is started immediately after the ultrasonic vibration and electric field action have ended and the liquid metal deposition is completed.

[0058] The substrate temperature is raised from the ambient temperature (approximately 25 °C) to the first target temperature W1 at a first heating rate of 2 °C / s. W1 is set to be 15 °C above the solidus temperature of the liquid metal, i.e., 5 °C (and satisfies W1 ≤ 60 °C).

[0059] Once W1 is reached, maintain this temperature for 30 seconds (first time s1).

[0060] During this heat preservation process, a first mechanical vibration is applied to the substrate. The frequency f1 of this vibration is 3 kHz, the amplitude A1 is 0.5 μm, and the vibration direction is perpendicular to the substrate surface.

[0061] 2. Second heating stage: After the first heating stage, the second heating stage begins. The substrate temperature is increased from W1 (5 °C) to the final curing temperature W2 at a second heating rate of 0.5 °C / s (lower than the first heating rate). W2 is set to 80 °C.

[0062] During the second heating process and in the initial heat preservation phase after reaching W2, a second mechanical vibration is applied to the substrate. The frequency f2 of this vibration is 100 Hz, the amplitude A2 is 5 μm, and the vibration direction is parallel to the substrate surface.

[0063] The second mechanical vibration is applied in an intermittent pulse mode: vibration duration τ on The interval is 5 seconds, and the resting time is τ. off It is 10 seconds, and satisfies τ. on <τ off .

[0064] 3. Curing process monitoring and control: Once the substrate temperature reaches W2 (80 ℃), timing begins, and real-time monitoring is started simultaneously.

[0065] A laser displacement sensor is used to monitor the height change of the liquid metal layer surface in real time and calculate its rate of change V. h .

[0066] Set a preset threshold V for determining when curing is complete. th The value is 0.05 μm / s. Based on the direct proportionality between Vth and the viscosity of the liquid metal (η, unit Pa·s) and the solidification shrinkage rate (ε, dimensionless), and combined with the alloy parameters of this embodiment, the formula Vth=k×η×ε (k is a proportionality constant, experimentally calibrated to 1.09×10⁻⁶) is used. 4 Calculated from μm・s / (Pa・%), Vth = 1.09 × 10⁻⁶ 4×0.002×2.3≈0.05 μm / s.

[0067] Continuous monitoring of V h When V is detected h When the velocity drops below 0.05 μm / s, the solidification of the liquid metal substrate is considered complete.

[0068] Once the solidification of the main body is determined to be complete, the application of the second mechanical vibration should be stopped immediately.

[0069] 4. Final static heat preservation: After the vibration stops, maintain the substrate temperature at W2 (80 ℃) and continue to keep it at a constant temperature.

[0070] Continue to maintain the temperature until the total heating time from the start of heating reaches 8 minutes, completing the final solidification of the liquid metal and forming a dense solid thermal interface with low internal stress.

[0071] Comparative Example 1 (without plasma treatment) The difference between this comparative example and Example 1 is that the plasma treatment in step S1 is omitted. Specifically, a ceramic substrate for a micro base station is taken and placed directly into a sealed process chamber without any surface treatment. Subsequent steps S2 to S4 are exactly the same as in Example 1: liquid metal droplet deposition is performed under inert gas conditions with the same parameters, ultrasonic vibration is applied, and finally, the substrate is heated and cured.

[0072] Comparative Example 2 (without inert gas protection) The difference between this comparative example and Example 1 is that the establishment of the inert gas environment in step S2 is omitted. Specifically, after plasma treatment of the substrate (with parameters the same as in Example 1), it is placed directly in an atmospheric environment (oxygen concentration of approximately 21%). Subsequent steps S3 and S4 are performed in air: liquid metal is deposited in an atmospheric environment and ultrasonic vibration is applied, followed by heating and curing.

[0073] Comparative Example 3 (Deposition without ultrasonic vibration assistance) The difference between this comparative example and Example 1 is that ultrasonic vibration is not applied in step S3. Specifically, after plasma treatment and establishing an inert gas environment, liquid metal is deposited using a microdroplet jetting device. The deposition parameters are the same as in Example 1, but no ultrasonic vibration is applied to the substrate throughout the deposition process. After deposition, heating and curing are performed directly.

[0074] Comparative Example 4 (Step-by-step processing in non-in-situ, non-sealed environments) In this comparative example, the substrate was first subjected to plasma treatment in an open environment (power 200 W, time 120 seconds). After treatment, the substrate was transferred in air to another device located in an atmospheric environment for liquid metal deposition (deposition parameters were the same as in Example 1). No ultrasonic vibration was applied during the deposition process, and no inert gas protection was used. After deposition, the sample was placed in an oven for air curing (80 °C, 5 minutes).

[0075] Effect test 1. Interfacial thermal performance indicators Method: A steady-state method was used to measure the overall thermal resistance from the substrate to the simulated heat sink connected through the formed interface. Under the same heat flux density, a lower interfacial thermal resistance indicates better thermal conductivity. The unit is K·cm. 2 / W.

[0076] 2. Interface morphology and uniformity index Methods: The interface layer thickness was measured at multiple measurement points within the effective area of ​​the interface using a white light interferometer or a laser confocal microscope. The average thickness (T) was calculated. avg ) and standard deviation (σ), with thickness variation coefficient (CV=σ / T) avg The CV value (×100%) is used as a uniformity evaluation index. The smaller the CV value, the more uniform the interface thickness.

[0077] 3. Interface oxidation degree index Methods: X-ray photoelectron spectroscopy (XPS) was used to analyze the composition of the formed solid interface surface, specifically the distribution of oxygen (O) content. A lower percentage of oxygen atoms indicates better anti-oxidation performance.

[0078] 4. Interface bonding strength index Method: Using a push-ball shear tester or a micro-force tester, a flat-head push rod of a specific size is aligned with and pressed against the solidified area of ​​the liquid metal on the interface. The push rod is advanced at a constant rate until interface failure occurs, and the maximum shear force is recorded. The shear strength is calculated based on the shear area. Unit: MPa. This indicator reflects the strength of the mechanical bond at the interface.

[0079] 5. Depositional area overlap Methods: The actual area (A) of the deposited pattern was analyzed using image processing software (ImageJ). 实际 ) and the area of ​​the preset target region (A) 目标 ), calculate the area overlap (A 实际 ∩A 目标 ) / A 目标 ×100%. The closer this value is to 100%, the more precise the deposition coverage of the target area.

[0080] 6. Cured interface quality Methods: The cured interface was reconstructed using non-destructive X-ray microscopy (micron-CT). The total volume fraction of observable microcracks and voids per unit volume of the interface was calculated using image analysis software, and this fraction was defined as the defect volume fraction. A lower value indicates better control of the curing process and a denser interface.

[0081] The results are shown in Table 1 below.

[0082] As shown in Table 1, the method proposed in this invention is significantly superior to traditional or simplified processes in several key indicators. In the comparative examples, due to the lack of plasma treatment, inert gas protection, ultrasonic vibration assistance, or being in an open environment, the interfacial thermal resistance is high (up to 1.65 K·cm). 2 The invention exhibits several drawbacks, including poor thickness uniformity (CV value up to 28.9%), severe surface oxidation (oxygen atom percentage up to 45.3%), low bonding strength (minimum only 4.1 MPa), insufficient deposition overlap (minimum 87.4%), and numerous internal defects (defect volume fraction up to 5.2%). These data clearly highlight the challenges of applying liquid metal in micro-base station assembly. In contrast, starting with Example 1, this invention has significantly improved various performance characteristics through the basic synergy of plasma treatment, ultrasonic-assisted deposition in an inert gas environment, and thermal curing. Subsequent examples, by gradually introducing advanced control methods such as in-situ passivation, electric field guidance and phase synchronization, dynamic activation by rotating electric fields, and staged gradient heating and vibration curing, further enhance the interface performance. Example 5, representing the integration of all optimization steps, demonstrates the best overall performance: the interface thermal resistance is reduced to 0.38 K·cm. 2 The thickness uniformity (CV=6.3%) and deposition overlap (98.3%) are both excellent, the oxidation degree is extremely low (oxygen atom percentage 3.7%), the bonding strength is as high as 19.2 MPa, and the internal defect volume fraction is only 0.5%. These data consistently demonstrate that the present invention effectively solves the problems of poor wettability, easy oxidation, uneven spreading, and stress concentration during curing of liquid metal on microscale substrates through a sophisticated process design involving multiple steps and multiple fields, thereby achieving in-situ self-formation of a high-performance, highly reliable thermally conductive interface.

[0083] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A method for in-situ self-formation of a liquid metal thermal interface in micro base station assembly, characterized in that, Includes the following steps: S1: Perform plasma treatment on the substrate of the micro base station. The plasma treatment power is 100-500 W and the treatment time is 30-300 seconds to increase the surface energy of the substrate. S2: Place the plasma-treated substrate into a sealed cavity, and introduce inert gas into the sealed cavity to reduce the oxygen concentration in the sealed cavity to below 100 ppm, thus forming an inert gas environment. S3: Liquid metal is deposited onto the effective area of ​​the substrate where a thermally conductive interface needs to be formed using a microdroplet jetting device. The nozzle diameter of the microdroplet jetting device ranges from 10 to 100 μm, the liquid metal deposition rate is 0.01 to 0.1 μL / s, and the deposited liquid metal covers 80% to 95% of the effective area surface area. In this process, while depositing liquid metal, ultrasonic vibration is applied to the substrate. The frequency of the ultrasonic vibration is 20-100kHz and the amplitude is 1-10μm. The application time of the ultrasonic vibration covers the entire process of liquid metal deposition. The shear force and cavitation effect generated by the vibration are used to promote the spread of liquid metal and remove its surface oxides. S4: After the liquid metal deposition and accompanying ultrasonic vibration steps are completed, the substrate is heated and cured at a temperature of 50-100 ℃ for 1-10 minutes to transform the liquid metal from a liquid state to a solid state, thereby forming a stable thermally conductive interface.

2. The in-situ self-formation method of liquid metal thermal interface in micro base station assembly according to claim 1, characterized in that, The plasma treatment step for the micro base station substrate is performed within a sealed cavity, specifically including: Before introducing inert gas into the sealed cavity, a mixed gas is first introduced into the sealed cavity as a plasma treatment atmosphere. The mixed gas consists of an inert gas and a silicon-containing organic gas, wherein the inert gas is argon and the silicon-containing organic gas is hexamethyldisilazane, and the volume flow ratio of argon to hexamethyldisilazane is 95:5-85:

15. Plasma treatment is carried out in a mixed atmosphere, with a power of 100-500 W and a treatment time of 30-300 seconds. After the plasma treatment is completed, the plasma power supply is turned off, the mixed gas continues to flow, and the substrate temperature is controlled at 50-80 ℃ for 30-120 seconds to allow hexamethyldisilazane to thermally decompose on the substrate surface to form a siloxane passivation layer with a thickness of 1-10 nm and a surface coverage of more than 90%. Stop introducing the mixed gas and introduce pure inert gas into the sealed cavity to replace the residual gas, so that the oxygen concentration in the sealed cavity drops below 100 ppm.

3. The in-situ self-formation method of liquid metal thermal interface in micro base station assembly according to claim 1, characterized in that, In the step of depositing liquid metal onto a substrate using a microdroplet jetting device, a DC electric field is applied between the nozzle of the microdroplet jetting device and the substrate. The DC electric field is applied by connecting the substrate to the positive terminal of the DC power supply and connecting the nozzle of the microdroplet ejection device to the negative terminal of the DC power supply. The electric field strength of a DC electric field is 0.5-5 kV / mm; The DC electric field is applied for a period of time covering the entire liquid metal deposition process, and the application of the DC electric field is carried out simultaneously with the application of ultrasonic vibration.

4. The in-situ self-formation method of liquid metal thermal interface in micro base station assembly according to claim 3, characterized in that, The DC electric field is applied in the form of a pulsed DC electric field; The pulse frequency of the pulsed DC electric field is the same as the frequency of the ultrasonic vibration, and the pulse frequency range is 20-100kHz. The pulse width of the pulsed DC electric field accounts for 20%-80% of a single pulse period; The pulse start time of the pulsed DC electric field is synchronized with the vibration signal of the ultrasonic vibration through a phase-locked circuit, with a synchronization error of less than 10 microseconds, so that the pulse start time of the pulsed DC electric field corresponds to the moment when the ultrasonic vibration displacement at the center point of the deposition area on the substrate surface reaches the positive maximum value.

5. The in-situ self-formation method of liquid metal thermal interface in micro base station assembly according to claim 4, characterized in that, The phase-locked circuit includes a vibration signal sensor, a signal conditioning module, a phase comparator, an adjustable delay unit, a voltage pulse detector, and a pulse generator; The vibration signal sensor is a piezoelectric accelerometer, which is attached to the surface of the transducer that applies ultrasonic vibration or to the vibration transmission component that is in direct contact with the substrate, and is used to collect the vibration signal of ultrasonic vibration in real time. The signal conditioning module is connected to the vibration signal sensor and is used to filter and amplify the collected vibration signal. The center frequency of the filtering band is the set frequency of the ultrasonic vibration, and the bandwidth is 10% of the set frequency, so as to extract a pure vibration reference signal. The first input terminal of the phase comparator is connected to the output terminal of the signal conditioning module to receive the vibration reference signal, and the second input terminal is connected to the feedback signal. The voltage pulse detector is used to acquire the pulse voltage signal actually applied between the substrate and the nozzle in real time, and sends the pulse voltage signal as a feedback signal to the second input terminal of the phase comparator. The input terminal of the adjustable delay unit is connected to the output terminal of the pulse generator, and the output terminal of the adjustable delay unit generates the control pulse signal for the final applied pulsed DC electric field. The phase comparator compares the phase of the vibration reference signal with the feedback signal and outputs an error voltage signal that is proportional to the phase difference between the two. The adjustable delay device dynamically adjusts its delay time according to the error voltage signal, with an adjustment range of 0-25 microseconds and an adjustment accuracy of 0.1 microseconds, so that the phase of the actual pulse voltage signal continuously tracks the phase of the vibration reference signal, thereby locking the pulse start time of the control pulse signal at the phase when the vibration reference signal reaches its positive maximum value.

6. The in-situ self-formation method of liquid metal thermal interface in micro base station assembly according to claim 1, characterized in that, Before the step of depositing liquid metal onto the substrate using a microdroplet jetting device, a surface dynamic activation step is performed first. The surface dynamic activation step is as follows: The ultrasonic vibration is activated, and the potential difference between the substrate and the nozzle of the microdroplet ejection device is linearly increased from zero to a preset pretreatment voltage within 1-5 seconds, and maintained for 5-30 seconds after reaching the pretreatment voltage. The electric field strength corresponding to the pretreatment voltage is 0.1 kV / mm to 0.5 kV / mm; the value of the pretreatment voltage increases the charge density on the substrate surface by 10%-50% without causing gas breakdown. After the surface dynamic activation step is completed, the ultrasonic vibration is maintained, and the potential difference between the substrate and the nozzle of the microdroplet jetting device is maintained at the state at the end of the surface dynamic activation step. At the same time, the microdroplet jetting device is turned on to start the deposition of liquid metal.

7. The in-situ self-formation method of liquid metal thermal interface in micro base station assembly according to claim 6, characterized in that, In the surface dynamic activation step, the electric field formed by the potential difference applied between the substrate and the nozzle is a rotating electric field; The rotating electric field is generated by two sets of mutually orthogonal electrode pairs, where the voltage applied to the first pair of electrodes is U. x =U0(t)×sin(ωt), the voltage applied to the second pair of electrodes is U y =U0(t)×cos(ωt), where U0(t) is the time-varying voltage amplitude that increases linearly from 0 to the value corresponding to the pre-processed voltage, ω is the angular frequency of the electric field rotation; sin(ωt) and cos(ωt) are functions that change periodically with time t; The electric field rotation angular frequency ω and the ultrasonic vibration frequency f satisfy the following relationship: ω=2π×n×f, where n is an integer and the value range is 1-10; During the surface dynamic activation step, the electric field rotation angular frequency ω remains constant as U0(t) increases linearly and is maintained. The direction of rotation of the rotating electric field remains unchanged.

8. The in-situ self-formation method of liquid metal thermal interface in micro base station assembly according to claim 1, characterized in that, In the step of heating and curing the substrate, a combination of staged gradient heating and synchronous micro-amplitude mechanical vibration is used, specifically including: After the ultrasonic vibration ends, the first heating stage is started, and the substrate temperature is raised from the ambient temperature to the first target temperature W1 at the first heating rate, and held at this temperature for a first time s1. The first heating rate is 1-5 ℃ / s, the first target temperature W1 is 10-20 ℃ above the solidus temperature of the liquid metal and W1≤60 ℃, and the first time s1 is 10-60 seconds. During the first heating stage, while maintaining the temperature, a first mechanical vibration is applied to the substrate. The frequency f1 of the first mechanical vibration is 1-5kHz, the amplitude A1 is 0.1-1 μm, and the vibration direction is perpendicular to the substrate surface. After the first heating stage is completed, the second heating stage begins, and the substrate temperature is raised from W1 to the final curing temperature W2 at a second heating rate. The curing temperature W2 is 50-100 °C. The second heating rate is lower than the first heating rate, at 0.2-1 ℃ / s; During the second heating process and the initial heat preservation period after reaching W2, a second mechanical vibration is applied to the substrate. The frequency f2 of the second mechanical vibration is 50-200 Hz, the amplitude A2 is 2-10 μm, and the vibration direction is parallel to the substrate surface. The second mechanical vibration is applied in an intermittent pulse mode, specifically: vibration duration τ on The interval between 2 and 10 seconds is the intermittent stillness time τ. off It lasts 5-20 seconds, and τ on <τ off ; The curing progress is determined by real-time monitoring of substrate temperature or curing process characteristic signals, and the timing of switching between vibration cessation and temperature maintenance is controlled accordingly. Specifically: Once the substrate temperature reaches W2, timing begins, and the physical signal reflecting the solidification state of the liquid metal is continuously monitored. This physical signal is the rate of change V of the liquid metal layer surface height, measured by a laser displacement sensor. h ; When V is detected h Drops below the preset threshold V th When the solidification of the liquid metal body is determined to be complete, the second mechanical vibration is stopped; V th The value is 0.01-0.1 μm / s, and V th The value of is directly proportional to the viscosity of the liquid metal and the curing shrinkage rate; After the vibration stops, maintain the substrate temperature at W2 and continue to heat it until the total heating time reaches the preset value, thus completing the final solidification of the liquid metal.

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