A method and system for regulating the thermal resistance of a package heat sink based on ultrasonic standing waves

Abstract

The application provides a packaging heat sink thermal resistance regulation and control method and system based on ultrasonic standing waves, comprising: performing ultrasonic impact global processing on a heat sink blank and then performing size stability processing; performing surface defect detection and matching the output parameters of focused ultrasonic impact; performing full-frequency acoustic characteristic testing on the target heat sink to construct acoustic-thermal parameters; after pre-assembly, in-situ monitoring of the target heat sink based on the acoustic-thermal parameters is performed on the double-frequency phase-locked ultrasonic standing waves and the interfacial thermal resistance; the parameters of the ultrasonic regulation and control system are dynamically adjusted until the interfacial thermal resistance reaches a preset target threshold, and a shaped ultrasonic signal is output to shape the target heat sink and the interfacial material. The application realizes accurate, efficient and stable regulation and control of the interfacial thermal resistance of the packaging heat sink through the whole process design, adapts to different target working temperature zones and heat sink materials, and significantly improves the heat dissipation efficiency and long-term service stability of the packaging heat sink.

Description

Technical Field

[0001] This application relates to the field of heat sink preparation, and more specifically, to a method and system for controlling the thermal resistance of a packaged heat sink based on ultrasonic standing waves. Background Technology

[0002] In the field of electronic device packaging, heat sinks, as core heat dissipation components, directly determine the heat dissipation efficiency and long-term service stability of devices through their interfacial thermal resistance with interface materials and packaging substrates. As electronic devices evolve towards higher power, miniaturization, and deep cryogenic compatibility, higher demands are placed on the precision and stability of thermal resistance control for packaged heat sinks.

[0003] Existing heat sink processing and thermal management solutions primarily rely on passive heat dissipation, making it difficult to proactively, flexibly, and precisely adjust the interface thermal resistance based on actual operating conditions. Conventional heat sink fabrication only completes blank forming, surface polishing, and basic flatness processing. After leaving the factory, the heat sink's structure and surface contact state remain fixed, and the interface thermal resistance is essentially solidified after assembly, making subsequent controllable adjustment impossible. Traditional ultrasonic optimization processes use fixed process parameters, failing to differentiate between individual heat sink material variations, surface defect variations, and temperature change characteristics. This prevents targeted changes to the interface contact state and material arrangement, thus hindering the proactive adjustment of interface thermal resistance values ​​as needed. Summary of the Invention

[0004] To address the problems existing in the current technology, this application provides a method and system for controlling the thermal resistance of a packaged heat sink based on ultrasonic standing waves. The specific solution is as follows:

[0005] A method for controlling the thermal resistance of a packaged heat sink based on ultrasonic standing waves, comprising: To obtain the heat sink blank, the heat sink blank is first subjected to ultrasonic impact treatment over its entire surface to eliminate residual internal stress, and then dimensional stability treatment is performed to obtain the pretreated blank. The surface defect detection is performed on the pretreated billet. Based on the defect detection results and the material mechanical and acoustic properties of the pretreated billet in the target working temperature range, the output parameters of focused ultrasonic impact are matched to perform selective area modification treatment on the pretreated billet to obtain the target heat sink. The target heat sink is subjected to full-band acoustic property testing. Based on the material's mechanical and acoustic properties, morphology and defect detection results, acoustic and thermal parameters bound to the target heat sink are constructed. After the target heat sink is pre-assembled with the interface material and the encapsulation substrate, the target heat sink is monitored in situ using a dual-frequency phase-locked ultrasonic standing wave and interface thermal resistance based on the acoustic and thermal parameters. Based on real-time monitoring of interface thermal resistance data and the aforementioned acoustic and thermal parameters, the parameters of the ultrasonic control system are dynamically adjusted until the interface thermal resistance reaches the preset target threshold. Then, a shaping ultrasonic signal is output to shape the target heat sink and interface material, thus completing the interface thermal resistance control.

[0006] In some specific embodiments, the ultrasonic shock full-domain processing specifically includes: adopting a dual-band ultrasonic synergistic shock mode, and pre-setting two ultrasonic shock signals of different frequency bands based on the material characteristics of the heat sink billet. One frequency band of ultrasound is used for the peeling and release of deep residual internal stress inside the billet, and the other frequency band of ultrasound is used for the elimination of residual internal stress on the surface of the billet and the preliminary optimization of the surface microstructure.

[0007] In some specific embodiments, during the surface defect detection, macroscopic defect parameters and microscopic defect parameters of the pretreated blank surface are acquired simultaneously. The macroscopic defect parameters include defect location, defect size, defect depth, and defect distribution density. The microscopic defect parameters include surface roughness, microcrack size, machining residual stress distribution, and surface grain distortion degree.

[0008] In some specific embodiments, the output parameters of the focused ultrasound shock include shock frequency band, focused power, shock amplitude, scanning path, and duration of action.

[0009] In some specific embodiments, if the surface defect detection results show that the larger the size and the deeper the defect, the corresponding focusing power and impact amplitude increase in a stepwise manner; if the surface defect detection results show that the micro-roughness is higher and the residual stress is more concentrated, the corresponding impact frequency band and action time are dynamically adjusted.

[0010] In some specific embodiments, the selective modification process includes forming a gradient functional layer on the surface of the pretreated billet. The gradient functional layer is distributed in a gradient from the surface layer to the substrate. The surface layer has a nanocrystalline structure to match the thermal expansion coefficient of the interface material, the middle layer has a micro-nano textured structure to improve the spreadability and anchoring effect of the interface material, and the bottom layer is a transition layer to achieve a smooth connection between the mechanical properties of the surface layer and the substrate.

[0011] In some specific embodiments, the frequency range of the full-band acoustic characteristic test covers the working frequency band of dual-frequency phase-locked ultrasonic standing waves. The test content includes the acoustic impedance, sound propagation velocity, sound attenuation coefficient, resonant frequency and phase response characteristics of the target heat sink. The test data are compared and analyzed with the acoustic characteristics of the pretreated billet to correct the acoustic characteristic deviation caused by selective area modification, and to provide accurate measured data support for the construction of acoustic and thermal parameters.

[0012] In some specific embodiments, the dual-frequency phase-locked ultrasonic standing wave includes a first ultrasonic signal and a second ultrasonic signal with a frequency band lower than the first ultrasonic signal; the first ultrasonic signal is used to regulate the bulk thermal resistance of the interface material, breaking the agglomeration structure of the thermally conductive filler in the interface material through high-frequency shearing effect and guiding its directional arrangement; the second ultrasonic signal is used to regulate the interface contact thermal resistance, filling the microscopic air gap of the interface through directional acoustic flow effect; the interface ultrasonic echo signal is collected in real time by the phase-locked loop, the phase difference between the incident wave and the reflected wave is compared, and the output phase of the first ultrasonic signal and the second ultrasonic signal is dynamically adjusted so that the antinode of the standing wave is always locked at the contact interface between the heat sink and the interface material.

[0013] In some specific embodiments, the switching between dual-frequency phase-locked ultrasonic standing wave and in-situ monitoring of interface thermal resistance is achieved through the same ultrasonic actuator to realize time-division multiplexing. During the in-situ monitoring of interface thermal resistance, the collected ultrasonic echo signal is converted into real-time interface thermal resistance data through the acoustic-thermal parameter model, and the body thermal resistance component and contact thermal resistance component of the interface thermal resistance are monitored simultaneously.

[0014] A packaged heat sink thermal resistance control system based on ultrasonic standing waves includes: The pretreatment unit is used to obtain the heat sink blank. First, the heat sink blank is subjected to ultrasonic impact treatment over its entire area to eliminate internal residual stress, and then dimensional stability treatment is performed to obtain the pretreated blank. The target heat sink unit is used to detect surface defects in the pretreated blank. Based on the defect detection results and the material mechanical and acoustic properties of the pretreated blank in the target working temperature range, the output parameters of focused ultrasonic impact are matched to perform selective modification treatment on the pretreated blank to obtain the target heat sink. The acoustic-thermal parameter unit is used to perform full-band acoustic characteristic testing on the target heat sink, and to construct acoustic-thermal parameters bound to the target heat sink by combining the material's mechanical and acoustic properties, morphology and defect detection results. An ultrasonic testing unit is used to perform dual-frequency phase-locked ultrasonic standing wave and in-situ monitoring of interface thermal resistance of the target heat sink based on the acoustic and thermal parameters after the target heat sink is pre-assembled with the interface material and the encapsulation substrate and the ultrasonic control system. The thermal resistance control unit is used to dynamically adjust the parameters of the ultrasonic control system based on the real-time monitored interface thermal resistance data and the acoustic-thermal parameters until the interface thermal resistance reaches the preset target threshold. It then outputs a shaping ultrasonic signal to shape the target heat sink and interface material, thus completing the interface thermal resistance control.

[0015] Beneficial Effects: This application proposes a method and system for controlling the thermal resistance of packaged heat sinks based on ultrasonic standing waves. It breaks through the limitations of existing technologies, such as the disconnect between heat sink preparation and thermal resistance control, the generalization of ultrasonic parameters, and the separation of control and monitoring. Through the whole-process design, it realizes the precise, efficient, and stable control of the thermal resistance of the packaged heat sink interface, adapts to different target operating temperature ranges and heat sink materials, significantly improves the heat dissipation efficiency and long-term service stability of the packaged heat sink, and provides a reliable thermal resistance control solution for the packaging of high-power, miniaturized, and cryogenically adaptable electronic devices. It has strong engineering application value and promotion prospects.

[0016] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the packaging heat sink thermal resistance control method of this application; Figure 2 This is a schematic diagram illustrating the principle of the thermal resistance control method for the encapsulated heat sink in this application; Figure 3 This is a schematic diagram of the defect detection process of this application; Figure 4 This is a schematic diagram of the dual-frequency ultrasonic control process of this application; Figure 5 This is a schematic diagram of the thermal resistance control system module for the heat sink in this application.

[0019] Figure reference numerals: 1-Preprocessing unit; 2-Target heat sink unit; 3-Acoustic and thermal parameter unit; 4-Ultrasonic detection unit; 5-Thermal resistance control unit. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0021] This application proposes a method for controlling the thermal resistance of a packaged heat sink based on ultrasonic standing waves. A schematic diagram of the method is attached. Figure 1 As shown in the attached diagram, the principle is as follows. Figure 2 As shown, the specific solution is as follows: A method for controlling the thermal resistance of a packaged heat sink based on ultrasonic standing waves, comprising: 101. Obtain the heat sink billet. First, the heat sink billet is subjected to ultrasonic impact treatment over the entire area to eliminate internal residual stress, and then dimensional stability treatment is performed to obtain the pretreated billet. 102. Surface defect detection is performed on the pretreated billet. Based on the defect detection results and the material mechanical and acoustic properties of the pretreated billet in the target working temperature range, the output parameters of focused ultrasonic impact are matched to perform selective area modification treatment on the pretreated billet to obtain the target heat sink. 103. Conduct full-band acoustic characteristic tests on the target heat sink, and construct acoustic and thermal parameters bound to the target heat sink by combining the material mechanical properties and acoustic properties, morphology and defect detection results; 104. After the target heat sink, interface material, and encapsulation substrate are pre-assembled, the target heat sink is monitored in situ using a dual-frequency phase-locked ultrasonic standing wave and interface thermal resistance based on acoustic and thermal parameters using an ultrasonic control system. 105. Based on real-time monitoring of interface thermal resistance data and acoustic-thermal parameters, dynamically adjust the parameters of the ultrasonic control system until the interface thermal resistance reaches the preset target threshold, output a shaping ultrasonic signal to shape the target heat sink and interface material, and complete the interface thermal resistance control.

[0022] This solution addresses the high-precision stress optimization, surface functional modification, and dedicated performance parameter documentation stages after the initial sintering and rough forming of the heat sink raw material, and before final precision machining and finished product delivery. It also connects downstream to the device packaging interface control process. Unlike the front-end raw material melting and preparation stages or the back-end packaging welding and curing stages, this solution is a core technology that bridges the upstream and downstream gaps in heat sink manufacturing and packaging heat dissipation control. It involves stress relief, dimensional stabilization, surface defect repair and modification, and acoustic-mechanical property calibration of the semi-finished heat sink, enabling it to adapt to precise thermal resistance control using dual-frequency ultrasonic standing waves. This fills the gap in traditional heat sink processes, which only perform shape processing and lack dedicated interface adaptation optimization. The heat sink blank is the original thermally conductive substrate blank, formed by melting thermally conductive raw materials, powder pressing and sintering, and rough cutting, possessing the basic outline dimensions of the heat sink. The blank contains a large amount of residual internal stress from molding, and its surface exhibits various macroscopic irregularities and microscopic structural defects. Without stress release stabilization treatment and surface functional modification, its overall dimensional stability and mechanical-acoustic properties do not meet the requirements for high-precision packaging heat dissipation. This blank is used as the initial substrate in this solution.

[0023] This application overcomes the limitations of existing technologies, such as the disconnect between heat sink preparation and thermal resistance control, the generalization of ultrasonic parameters, and the separation of control and monitoring. Through a comprehensive design encompassing pretreatment, surface modification, dedicated parameter construction, synergistic control, and finalization, it achieves precise, efficient, and stable control of the interface thermal resistance of the encapsulated heat sink. This method specifically addresses the core pain points of existing technologies, including high interface thermal resistance, low control precision, poor stability, low yield in mass production, and high debugging costs. It is adaptable to different target operating temperature ranges and heat sink materials, significantly improving the heat dissipation efficiency and long-term service stability of the encapsulated heat sink. It provides a reliable thermal resistance control solution for the packaging of high-power, miniaturized, and cryogenically adaptable electronic devices, possessing strong engineering application value and promising prospects for widespread application.

[0024] Step 101 is the basic pretreatment step for thermal resistance control. Its core function is to eliminate internal defects in the heat sink billet and stabilize the billet size, so as to provide a substrate with uniform performance and stable size for subsequent surface modification and thermal resistance control, and avoid the increase of interface thermal resistance due to billet deformation and internal stress release during subsequent processing or service.

[0025] First, a heat sink blank that meets the packaging requirements is selected. Common heat sink materials such as copper, diamond copper, and ceramics can be chosen based on the device's heat dissipation needs. For example, a 5mm thick oxygen-free copper blank is selected as the heat sink blank, as this material combines good thermal conductivity and mechanical strength, suitable for the packaging requirements of most medium- and high-power electronic devices. Then, the heat sink blank undergoes full-area ultrasonic impact treatment. The high-frequency mechanical vibration effect generated by ultrasonic vibration induces dislocation movement and grain rearrangement of atoms within the blank, thereby peeling off and releasing residual internal stress generated during the melting and rolling processes. If this residual internal stress is not eliminated, it will be gradually released during subsequent machining, ultrasonic modification, or service temperature changes, leading to warping and deformation of the blank, increasing the contact gap between the heat sink and the interface material, and significantly increasing the interface thermal resistance. Full-area ultrasonic impact treatment must cover the entire surface and internal area of ​​the blank, including edges, corners, and other areas prone to residual internal stress, ensuring no dead corners with residual internal stress, and ensuring uniform stress distribution within the blank to avoid localized deformation and cracking during subsequent processing.

[0026] After ultrasonic impaction, the billet undergoes dimensional stability treatment. Specific temperature-induced deformation or aging processes are used to further release residual micro-stress from the ultrasonic impact, while simultaneously stabilizing the billet's microcrystalline structure, fixing its dimensions, and preventing irreversible deformation at the target operating temperature range (e.g., room temperature or cryogenic temperatures). The core purpose of dimensional stability treatment is to adapt the billet's thermal expansion characteristics to the target operating temperature range, reducing dimensional fluctuations during temperature changes and ensuring the accuracy of subsequent surface modification and packaging assembly. For example, dimensional stability treatment can employ a temperature-induced cycling method, cycling the billet three times within the range of -50℃ to 80℃, holding each cycle at that temperature for 2 hours. Through repeated temperature-induced stress induction, the internal grains of the billet are fully stabilized, and the dimensions are solidified, ultimately yielding a pre-treated billet. The pre-treated billet must meet core qualification standards: internal stress distribution deviation ≤10%, and dimensional deviation ≤1μm / m. This ensures the accuracy of subsequent surface defect detection and the precision of surface modification, providing a reliable guarantee for the smooth implementation of subsequent steps.

[0027] Step 102 is the core step in optimizing the heat sink surface and reducing interfacial thermal resistance. Its core function is to accurately detect the surface state and material properties of the pretreated billet, customize and match ultrasonic modification parameters, and perform directional optimization of the billet surface to eliminate surface defects and improve the compatibility between the heat sink and the interfacial material.

[0028] First, surface defect detection is performed on the pretreated billet obtained in step 101. Conventional detection equipment (such as laser profilometer and atomic force microscope) is used to comprehensively detect defects on the billet surface in a macroscopic-to-microscopic order, ensuring that the detection covers all contact surfaces of the billet (i.e., the surfaces that will subsequently bond with the interface material). The condition of these contact surfaces directly determines the tightness of the contact between the heat sink and the interface material and is the main area where interfacial thermal resistance is generated; therefore, defect detection must be comprehensive and accurate. After the detection is completed, a complete defect detection result is obtained, clarifying the distribution, type, and specific parameters of defects on the billet surface, providing a precise targeting basis for subsequent selective modification. Simultaneously, the mechanical and acoustic properties of the pretreated billet are tested within the target operating temperature range. These two types of properties are the core basis for matching focused ultrasonic impact parameters, and neither can be omitted. Mechanical properties primarily reflect the billet's strength, toughness, and thermal expansion characteristics, used to determine the power and upper limit of the ultrasonic impact, avoiding plastic deformation and surface damage during the impact process. Acoustic properties primarily reflect the billet's propagation, reflection, and attenuation characteristics of ultrasonic signals, used to determine the frequency band of the ultrasonic impact, ensuring that ultrasonic energy can be efficiently transferred to the billet surface, achieving defect repair and surface optimization, and avoiding poor modification effects due to wasted ultrasonic energy or inefficient transmission. For example, if the target operating temperature range is -50℃, the elastic modulus, coefficient of thermal expansion (mechanical properties), acoustic impedance, and sound propagation velocity (acoustic properties) of the billet at this temperature are tested. If the tests reveal that the billet has a low elastic modulus and poor toughness within this temperature range, the amplitude of the ultrasonic impact needs to be reduced to avoid damage to the billet.

[0029] Subsequently, based on the aforementioned defect detection results, material mechanical properties, and acoustic properties, the output parameters of focused ultrasonic impact are matched. This customized parameter matching method, unlike the universal ultrasonic parameter templates in existing technologies, enables precise modification, ensuring that the modification effect is adapted to the individual characteristics of the heat sink. The matching logic is as follows: combining the type, size, and distribution of defects, the key areas for ultrasonic impact (i.e., selected areas) are determined, and concentrated defect areas are impacted with emphasis, while defect-free areas are slightly optimized to avoid ineffective impact; combining the material mechanical properties, the upper limit of ultrasonic impact power and amplitude is determined to ensure that the ultrasonic impact force is within the tolerance range of the billet, avoiding plastic deformation and surface peeling of the billet during the impact process; combining the acoustic properties, the frequency band of ultrasonic impact is determined so that the ultrasonic signal can form a good coupling with the billet, ensuring that the ultrasonic energy is efficiently transferred to the defect area, achieving defect repair and surface optimization.

[0030] For example, if a 2μm deep and 5μm diameter depression defect is detected on the surface of the pretreated blank, and the blank has a low elastic modulus at the target temperature range, a lower ultrasonic amplitude and moderate power are used to focus the impact on the depression defect area. The mechanical effect of the ultrasound causes a small amount of plastic flow in the surface metal of the blank, filling the depression and smoothing the defect. Simultaneously, a light ultrasonic impact is applied to the entire blank surface to optimize surface smoothness, reduce surface roughness, and increase the contact area between the heat sink and the interface material. Finally, the selected area modification treatment is completed, resulting in a target heat sink with eliminated surface defects and a surface state compatible with the interface material. The contact surface of the target heat sink must meet the standards of defect depth ≤0.5μm and surface smoothness ≤2μm, laying a good foundation for subsequent packaging assembly and thermal resistance control, ensuring that the target heat sink can meet the requirements of subsequent thermal resistance control.

[0031] Step 103 is the core prerequisite for achieving precise control of thermal resistance. Its core function is to construct acoustic and thermal parameters that are uniquely compatible with the target heat sink, providing a customized parameter benchmark for subsequent ultrasonic control and solving the problems of poor adaptability and low control accuracy of general parameter templates in existing technologies.

[0032] First, the target heat sink obtained in step 102 undergoes full-band acoustic characteristic testing. The test frequency range must fully cover the ultrasonic standing wave frequency band used in subsequent ultrasonic control to ensure that the test data can directly support subsequent parameter matching and avoid parameter mismatch due to incomplete frequency band coverage, which would affect the control effect. The test content includes the acoustic impedance, sound propagation velocity, sound attenuation coefficient, resonant frequency, and phase response characteristics of the target heat sink. The test clarifies the response law of the target heat sink to ultrasonic signals in different frequency bands, as well as the changes in the acoustic characteristics of the heat sink after selective modification. Selective modification will change the microstructure of the heat sink surface, resulting in differences in its acoustic characteristics compared to the pretreated blank. If full-band acoustic characteristic testing is not performed and the acoustic parameters of the pretreated blank are directly used, it will lead to mismatch in subsequent ultrasonic control parameters, making precise control impossible.

[0033] Subsequently, combining the material mechanical and acoustic properties of the pretreated billet obtained in step 102, the surface defect detection results, and the full-band acoustic property test results, acoustic-thermal parameters are constructed. The core of these acoustic-thermal parameters is establishing the correspondence between ultrasonic control parameters and interfacial thermal resistance. Simultaneously, the material properties and surface state parameters of the heat sink are incorporated to ensure the parameters' unique adaptability. Each target heat sink corresponds to a unique set of acoustic-thermal parameters, avoiding parameter confusion between different heat sinks and ensuring consistent control effects for each heat sink during mass production. The construction of acoustic-thermal parameters must adhere to the principle of being based on measured data and centered on logical connections. All parameters are derived from measured data in previous steps; no parameters are arbitrarily set, ensuring the scientific validity and feasibility of the parameters.

[0034] For example, by combining the acoustic resonant frequency of the target heat sink, the fundamental frequency band of the subsequent dual-frequency phase-locked ultrasonic standing wave is determined, enabling the ultrasonic signal to resonate with the target heat sink and maximizing the ultrasonic modulation effect. By combining the thermal expansion coefficient in the material's mechanical properties, the power adjustment boundary for ultrasonic modulation is determined to avoid ultrasonic parameter failure due to changes in heat sink size during temperature changes. By combining surface defect detection results, the initial parameter benchmark for ultrasonic modulation is determined, setting initial modulation parameters for the modified surface state to reduce the amplitude and time of subsequent parameter adjustments. By combining the acoustic attenuation coefficient, the transmission loss compensation parameter for the ultrasonic signal is determined to ensure that ultrasonic energy can be stably transmitted to the contact interface between the heat sink and the interface material, avoiding a decrease in modulation effect due to energy loss. Finally, acoustic-thermal parameters bound to the target heat sink are constructed. These acoustic-thermal parameters are only suitable for the target heat sink prepared in this study, accurately reflecting the correlation between the heat sink's characteristics and ultrasonic modulation, providing precise parameter support for subsequent steps.

[0035] Step 104 is the implementation step of thermal resistance control. Its core function is to complete the pre-assembly of the heat sink, realize the synergy between ultrasonic control and interface thermal resistance monitoring, and provide real-time feedback for subsequent dynamic adjustment of ultrasonic parameters.

[0036] First, the target heat sink, interface material (such as thermally conductive silicone, solder), and packaging substrate (such as device housing) obtained in step 102 are pre-assembled according to packaging requirements. The core requirement of pre-assembly is to ensure that the target heat sink and interface material are tightly bonded, and that the interface material uniformly fills the gap between the heat sink and the packaging substrate, forming a complete contact interface between the heat sink, interface material, and packaging substrate. Interface thermal resistance is generated at this contact interface, and its magnitude is directly related to the tightness of contact and the filling state of the interface material. Only by completing the pre-assembly and forming a complete contact interface can the monitoring and control of interface thermal resistance be realized. This is a prerequisite for the smooth implementation of subsequent ultrasonic control and in-situ monitoring. During the pre-assembly process, the pressing pressure and assembly accuracy need to be controlled. For example, the pressing pressure should be controlled at 0.5 or 1 MPa to avoid excessive pressure damaging the heat sink or interface material, and insufficient pressure leading to excessive interface gaps. The assembly accuracy should be controlled at ±0.1 μm to ensure that the heat sink and packaging substrate are aligned, and to avoid displacement of the ultrasonic standing wave action position due to assembly deviation, which would affect the control effect.

[0037] After pre-assembly, the ultrasonic control system is activated. Based on the acoustic and thermal parameters constructed in step 103, the ultrasonic control system is initialized, importing the basic control parameters and compensation parameters from the acoustic and thermal parameters into the ultrasonic control system. This ensures that the output parameters of the ultrasonic control system are compatible with the characteristics of the target heat sink, avoiding control failure or material damage caused by improper parameter initialization. Subsequently, the ultrasonic control system outputs a dual-frequency phase-locked ultrasonic standing wave, which acts on the target heat sink. Simultaneously, in-situ monitoring of interface thermal resistance is performed, achieving simultaneous control and monitoring. This breaks the disconnect between control and monitoring in existing technologies, enabling real-time capture of changes in interface thermal resistance and providing timely and accurate feedback for subsequent parameter adjustments.

[0038] The core of dual-frequency phase-locked ultrasonic standing wave technology lies in its synergistic effect of two different frequency bands of ultrasonic signals to specifically regulate interfacial thermal resistance. This differs from the limitations of single-frequency ultrasonic regulation in existing technologies, simultaneously addressing both interfacial contact thermal resistance and the thermal resistance of the interfacial material itself, thus improving regulation efficiency and effectiveness. Phase-locked control ensures that the antinodes of the ultrasonic standing wave remain stable at the interface between the heat sink and the interfacial material through real-time phase calibration, maximizing the ultrasonic regulation effect and avoiding regulation blind spots caused by antinode deviation. This ensures that ultrasonic energy is precisely applied to the interfacial region, achieving efficient regulation of interfacial thermal resistance. In-situ monitoring utilizes the monitoring module of the ultrasonic regulation system to collect ultrasonic echo signals from the interface in real time. By leveraging the correspondence between ultrasonic echo signals and interfacial thermal resistance in acoustic-thermal parameters, the echo signals are converted into real-time interfacial thermal resistance data, simultaneously acquiring the overall value and trend of interfacial thermal resistance, providing feedback for subsequent parameter adjustments.

[0039] For example, during pre-assembly, the target heat sink is aligned and pressed with the thermally conductive silicone and the device shell to ensure that the bonding gap does not exceed 1μm; the ultrasonic control system initializes the basic frequency band and power of the dual-frequency ultrasonic signal based on acoustic and thermal parameters, outputs dual-frequency phase-locked ultrasonic standing waves, and at the same time collects the interface echo signal every 10ms through the monitoring module, quickly converts it into interface thermal resistance data, and provides real-time feedback on the current thermal resistance status, realizing the synchronous operation of control and monitoring, laying the foundation for subsequent dynamic adjustment of parameters.

[0040] Step 105 is the final step in thermal resistance control. Its core function is to precisely control the interfacial thermal resistance within a preset range by dynamically adjusting the ultrasonic parameters. At the same time, through shaping treatment, the microstructure of the heat sink and the interfacial material is fixed to ensure the long-term stability of the interfacial thermal resistance.

[0041] First, obtain the interface thermal resistance data monitored in real time in step 104, and compare this data with the preset target threshold to determine whether the current interface thermal resistance meets the standard. The preset target threshold is not a fixed value, but is determined comprehensively based on factors such as the heat dissipation requirements of the device, the thermal conductivity of the interface material, and the target operating temperature range. For example, the preset target threshold for high-power electronic devices can be set to ≤4×10⁻⁶. 、4 m²·K / W, for ordinary electronic devices, can be set to ≤6×10 、4 m²·K / W, ensuring that the target threshold matches the actual heat dissipation requirements of the device.

[0042] If the target is not met, the parameters of the ultrasonic control system are dynamically adjusted based on real-time interface thermal resistance data and acoustic-thermal parameters. The adjustment process employs closed-loop control logic to ensure the accuracy and efficiency of parameter adjustment. The adjustment logic is as follows: combining the correspondence between ultrasonic parameters and interface thermal resistance in the acoustic-thermal parameters, the core reasons for the current interface thermal resistance exceeding the standard are first analyzed (such as excessive interface contact gap, agglomeration of thermally conductive fillers in the interface material, etc.). Then, according to the degree of exceeding the standard, the power, frequency band, phase, and other parameters of the dual-frequency ultrasonic standing wave are adjusted in a targeted manner to gradually reduce the interface thermal resistance and avoid control failure or material damage caused by blind adjustment. For example, if monitoring finds that the interface thermal resistance is higher than the preset threshold, and it is determined by acoustic-thermal parameters that it is caused by excessive interface contact gap, the power of the low-frequency ultrasonic signal is adjusted. Through the directional acoustic flow effect of ultrasound, the interface material is pushed to fill the contact gap, reducing the interface air gap and lowering the interface contact thermal resistance. If it is determined that it is caused by agglomeration of thermally conductive fillers in the interface material, the power of the high-frequency ultrasonic signal is adjusted. Through the high-frequency shearing effect, the agglomeration of fillers is broken, so that the thermally conductive fillers are evenly distributed, improving the thermal conductivity of the interface material and reducing the interface body thermal resistance.

[0043] The above adjustment process continues until the real-time monitored interfacial thermal resistance reaches the preset target threshold and remains stable for more than 30 seconds, ensuring stable thermal resistance control and avoiding subsequent rebound due to instantaneous achievement of the target. At this point, the ultrasonic control system outputs a shaping ultrasonic signal to shape the target heat sink and interfacial material. The core function of the shaping ultrasonic signal is to fix the surface microstructure of the target heat sink (such as the modified surface smoothness and nanocrystalline structure) and the microstate of the interfacial material (such as the arrangement of thermally conductive fillers and the interfacial filling effect), preventing changes in the microstructure of the heat sink and interfacial material during subsequent encapsulation, curing, or service, which could lead to a rebound in interfacial thermal resistance and ensure the long-term stability of the interfacial thermal resistance. The parameters of the shaping ultrasonic signal need to be dynamically determined based on the acoustic and thermal parameters and the target interfacial thermal resistance status. For example, the frequency band should be consistent with the resonant frequency of the target heat sink, the power should be 50% of the control power, and the duration should be 30-60 seconds to achieve effective shaping without damaging the heat sink and interfacial material.

[0044] After finalization, the ultrasonic control system is turned off, and a second interface thermal resistance test is performed on the controlled encapsulated heat sink to confirm that the thermal resistance data is stable within the preset target threshold range without any rebound. This completes the entire interface thermal resistance control process for the encapsulated heat sink. For example, when the interface thermal resistance monitoring data stabilizes at 4.8 × 10⁻⁶... -4 When m²·K / W (reaching the preset threshold) is reached, a low-power shaping ultrasonic signal is output and applied for 30 seconds to fix the microstructure of the heat sink and interface material. After standing for 1 hour, the signal is monitored again to confirm that there is no significant change in the thermal resistance data, ensuring that the interface thermal resistance remains stable within the preset range for a long time.

[0045] In some specific embodiments, the ultrasonic shock full-domain processing specifically includes: adopting a dual-band ultrasonic synergistic shock mode, and pre-setting two ultrasonic shock signals of different frequency bands based on the material characteristics of the heat sink billet. One frequency band of ultrasound is used for the peeling and release of deep residual internal stress inside the billet, and the other frequency band of ultrasound is used for the elimination of residual internal stress on the surface of the billet and the preliminary optimization of the surface microstructure.

[0046] In some specific embodiments, during surface defect detection, macroscopic and microscopic defect parameters of the pretreated billet surface are acquired simultaneously. Macroscopic defect parameters include defect location, defect size, defect depth, and defect distribution density. Microscopic defect parameters include surface roughness, microcrack size, machining residual stress distribution, and surface grain distortion degree. The defect detection process is as follows: Figure 3 As shown.

[0047] Even after stress relief and dimensional stability treatment, structural defects of varying scales still exist on the surface of the heat sink blank. Large-scale morphological deviations directly cause poor adhesion between the heat sink and the interface material, resulting in large-area contact gaps. Microscopic surface defects continue to expand during temperature changes, leading to interface debonding and thermal resistance drift. Traditional single-dimensional inspection can only acquire surface unevenness and cannot cover all types of defects affecting interface heat dissipation. Therefore, this solution simultaneously collects macroscopic and microscopic defect parameters to fully reconstruct the true surface condition.

[0048] Macroscopic defect parameters are mainly used to quantitatively collect large-scale visible morphological anomalies on the heat sink surface, specifically including defect location, defect size, defect depth, and defect distribution density.

[0049] Defect location is used to pinpoint specific areas of protrusions, depressions, and other structures on the heat sink bonding surface, allowing subsequent focused ultrasound to precisely target the defect area without requiring additional ultrasonic treatment of the intact surface, thus avoiding unnecessary vibration affecting the normal structure. Defect size is used to determine the extent of defect planar extension, thereby determining the ultrasonic impact coverage area. Defect depth is used to determine the vertical undulation height of the defect, directly determining the energy intensity required for ultrasonic impact. Defect distribution density is used to determine the density of defects across the entire surface, distinguishing between areas requiring key reinforcement and minor optimization. These parameters can optimize the surface flatness of the heat sink from an overall perspective, avoiding large air gaps after encapsulation and reducing interfacial contact thermal resistance from the source. Microscopic defect parameters mainly collect data on micron and submicron level hidden defects and structural stress states on the heat sink surface, specifically including surface roughness, microcrack size, machining residual stress distribution, and surface grain distortion degree. Surface roughness reflects the uniformity of surface undulations; excessive roughness prevents the interfacial material from completely filling micro-gaps, leaving insulating micro-voids and significantly increasing interfacial thermal resistance. Microcrack size is used to identify minute cracks that are difficult to detect on the surface. These cracks will continue to expand under deep cryogenic shrinkage conditions, eventually causing interfacial delamination failure. Machining residual stress distribution is used to identify localized stress concentration points. Areas with abnormal stress will spontaneously warp and deform under temperature changes, compromising interfacial adhesion stability. The degree of surface grain distortion reflects the regularity of the crystal arrangement on the heat sink surface. Disordered grains not only reduce the heat sink's own thermal conductivity but also weaken the interfacial bonding effect. These parameters can optimize the density and long-term stability of the heat sink surface structure, preventing a continuous increase in interfacial thermal resistance during service and ensuring stable heat dissipation performance under deep cryogenic cycling conditions.

[0050] Macroscopic and microscopic defect parameters complement each other and are indispensable. Detecting only macroscopic defects cannot uncover hidden cracks and localized stress anomalies, while detecting only microscopic defects cannot control the overall surface flatness. By combining these two types of parameters and linking them with the mechanical and acoustic properties of the pretreated billet, it is possible to differentiate and match the focused ultrasonic impact intensity, duration, and scanning path for different regions.

[0051] Meanwhile, the complete defect data of this batch will be incorporated into the subsequent acoustic and thermal parameter construction process, so that the ultrasonic standing wave control in the packaging stage can also be adapted to the actual surface state of the heat sink, realizing a unified closed loop of parameters for the entire process of heat sink preparation, surface modification, and packaging thermal resistance control, comprehensively suppressing the generation of interface voids and continuously and stably reducing the thermal resistance of the packaging interface.

[0052] In some specific embodiments, the output parameters of focused ultrasonic impact include impact frequency band, focused power, impact amplitude, scanning path, and duration. The impact frequency band is the core parameter for ultrasonic energy transfer, determining the frequency characteristics of ultrasonic vibration and directly affecting the penetration depth and action mode of ultrasonic energy on the heat sink surface. It adapts to the acoustic characteristics of the pretreated billet, ensuring efficient transfer of ultrasonic energy to the defect area and avoiding excessive energy loss or excessive penetration that could damage the billet matrix. The focused power is the energy intensity benchmark for ultrasonic impact, determining the force of the ultrasonic action and directly related to the efficiency and effect of defect repair. It needs to be determined in conjunction with the size and depth of the defect and the mechanical properties of the billet to avoid excessive power causing plastic deformation of the heat sink or insufficient power failing to complete defect repair. The impact amplitude is the displacement amplitude of ultrasonic vibration, working in conjunction with the focused power to further refine the intensity of the ultrasonic action, adapting to defects of different sizes and depths, ensuring precise impact repair of defective areas while avoiding unnecessary damage to defect-free areas. The scanning path is the trajectory of the ultrasonic impact. Based on the location and distribution density of surface defects in the pretreated billet, it achieves the core requirement of selective modification: precise coverage of defect areas and no redundant action on defect-free areas. This ensures that the ultrasonic impact only acts on the defective areas that need repair, improving modification efficiency and reducing energy consumption. The impact duration is the dwell time of the ultrasonic impact in each defective area. It is determined in conjunction with the defect size, depth, and distribution density to ensure that defects can be fully repaired, while avoiding excessive distortion of surface grains due to excessive impact time in a single area, thus ensuring the stability of the microstructure of the heat sink surface.

[0053] In some specific embodiments, if the surface defect detection results show that the larger the size and the deeper the defect, the corresponding focusing power and impact amplitude increase in a stepwise manner; if the surface defect detection results show that the micro-roughness is higher and the residual stress is more concentrated, the corresponding impact frequency band and action time are dynamically adjusted.

[0054] If the surface defect detection results show that the larger and deeper the defect, the corresponding focused power and impact amplitude will increase in a stepwise manner. The core principle is that large and deep defects (such as large dents and deep scratches) require stronger ultrasonic energy to be repaired. The focused power determines the overall energy intensity of the ultrasonic impact, and the impact amplitude determines the displacement amplitude of the ultrasonic vibration. The stepwise increase of both ensures that the ultrasonic energy increases synchronously with the severity of the defect, achieving full repair. For example, when a defect size of 3μm and a depth of 1μm is detected, the basic focused power and impact amplitude are matched; when the defect size increases to 5μm and the depth increases to 2μm, the focused power increases by 30% and the impact amplitude increases by 25%; when the defect size reaches 8μm and the depth reaches 3μm, the focused power increases by another 20% and the impact amplitude increases by another 20%. Through this stepwise increase, it is ensured that large and deep defects can be completely repaired, while avoiding damage to the heat sink surface caused by excessive power and amplitude.

[0055] If the surface defect detection results show higher micro-roughness and more concentrated residual stress, the impact frequency and duration will be dynamically adjusted accordingly. The core principle is that high micro-roughness requires a suitable ultrasonic frequency to smooth out minor surface undulations, while areas of concentrated residual stress require sufficient ultrasonic treatment time to release stress and optimize the surface grain structure. For example, when the micro-roughness of the pretreated billet surface is detected to be Ra 0.8 μm and the residual stress distribution is uniform, a conventional impact frequency and duration are used; when the micro-roughness increases to Ra 1.2 μm and residual stress becomes locally concentrated, the impact frequency is appropriately increased to enhance the smoothing effect of ultrasound on minor undulations, while the treatment time is extended to ensure that the stress in the concentrated stress area is fully released and the surface grain distortion is improved; when the micro-roughness decreases to Ra 0.5 μm and the residual stress tends to be uniform, the impact frequency is adjusted back to the conventional range, and the treatment time is shortened to avoid excessive impact causing damage to the surface structure.

[0056] In some specific embodiments, the selective modification process includes forming a gradient functional layer on the surface of the pretreated billet. The gradient functional layer is distributed in a gradient from the surface layer to the substrate. The surface layer has a nanocrystalline structure to match the thermal expansion coefficient of the interface material, the middle layer has a micro-nano textured structure to improve the spreadability and anchoring effect of the interface material, and the bottom layer is a transition layer to achieve a smooth connection between the mechanical properties of the surface layer and the substrate.

[0057] The core feature of the gradient functional layer is its gradient distribution along the direction from the surface to the substrate. It is not a three-layer, independently assembled structure, but rather achieves a continuous transition in grain structure, mechanical properties, and thermophysical properties from the surface to the substrate through gradient control of the energy, frequency band, and duration of focused ultrasonic impact. The surface layer focuses on thermal expansion adaptation, the middle layer on interfacial bonding and spreading, and the bottom layer on structural connection and stress dispersion. These three layers work synergistically and are indispensable, forming a complete structural optimization system that avoids problems such as insufficient adaptation, weak interfacial bonding, and easy surface detachment caused by single-layer surface modification.

[0058] The surface layer employs a nanocrystalline structure. The core principle is that the thermal expansion coefficients of the heat sink substrate and the interface material naturally differ. During temperature fluctuations (especially in cryogenic conditions), the amplitude of their thermal expansion and contraction is inconsistent, easily leading to interfacial gaps or localized stress concentrations, directly causing a surge in interfacial thermal resistance. The nanocrystalline structure, through the plastic deformation effect of focused ultrasonic impact, breaks down and refines the coarse grains on the surface of the pretreated blank, forming a dense structure with nanoscale grains. Its thermal expansion coefficient can be precisely controlled by the degree of grain refinement, thereby achieving a match with the thermal expansion coefficient of the interface material.

[0059] The core function of the surface layer is to eliminate interfacial gaps caused by temperature changes from the perspective of thermal expansion adaptation, prevent interfacial debonding under deep cryogenic conditions, ensure long-term adhesion between the heat sink and the interfacial material, and suppress the increase of interfacial thermal resistance from the source. For example, if the pretreated billet is an oxygen-free copper substrate (with a thermal expansion coefficient of approximately 17 × 10⁻⁶), -6 / ℃), the interface material is silicone thermally conductive silicone (thermal expansion coefficient approximately 22×10). -6 / ℃), then by ultrasonic impact, the copper surface layer is refined into a nanocrystalline structure, and its thermal expansion coefficient is controlled to 20×10. -6 At approximately ℃, precise adaptation with the interface material is achieved, avoiding interfacial gaps at deep low temperatures. The surface layer implementation requires combining the acoustic characteristics of the pretreated billet and the results of surface defect detection to select an appropriate impact frequency band and duration for focused ultrasonic impact on the surface area. Specifically, the location and distribution of surface defects are first determined through surface defect detection. Then, based on the acoustic characteristics of the billet, a high-frequency ultrasonic band (e.g., 20-50kHz) is selected to ensure precise application of ultrasonic energy to the surface, avoiding excessive penetration and damage to the matrix. Simultaneously, the impact amplitude and duration are controlled to allow dynamic recrystallization of the coarse surface grains, gradually refining them into nanocrystalline structures with grain sizes of 50-200nm, ultimately forming a dense surface nanocrystalline structure.

[0060] The intermediate layer features a micro / nano-textured structure. The core principle is that this micro / nano-texture is a micrometer- to submicrometer-scale uneven structure formed between the surface nanocrystals and the underlying substrate. Compared to a smooth surface, it significantly increases the contact area between the heat sink and the interface material, while providing physical space for the interface material to spread and anchor. The micro / nano-texture is formed through selective application of focused ultrasonic impact; it is not random surface roughness, but rather a regular uneven structure planned based on defect detection results, effectively guiding the flow and filling of the interface material.

[0061] The core functions of the intermediate layer are twofold: first, to improve the spreadability of the interface material, preventing agglomeration and insufficient leveling on the heat sink surface, ensuring uniform coverage of the heat sink surface; second, to construct a physical anchoring structure, allowing the thermally conductive filler or bulk material of the interface material to penetrate into the texture gaps, forming a mechanically interlocking bond, strengthening the interface bonding strength, reducing microscopic air gaps at the interface, and lowering the interface thermal resistance from the perspectives of contact area and interface anchoring. For example, when there are local depression defects on the surface of the pretreated blank, a micro-nano texture is constructed for the area surrounding the depression, with the texture depth controlled at 10μm and the spacing at 20μm. Subsequent thermally conductive silicone can completely fill the texture gaps, forming a strong mechanical anchor, while increasing the contact area by more than 30% compared to a smooth surface, effectively reducing contact thermal resistance. The implementation of the intermediate layer requires planning a precise scanning path based on the defect distribution density and micro-roughness data from surface defect detection, and performing ultrasonic impact on the defect area and the surrounding optimized area. In practice, based on the size and depth of the defect, the impact power and amplitude are matched in a step-by-step manner to form a micro-nano texture with a depth of 5~20μm and a spacing of 10~30μm under the surface nanocrystals. At the same time, combined with the mechanical properties of the blank, the impact time is controlled to avoid the surface nanocrystal structure from being damaged due to excessive texture, thus ensuring the connection stability between the texture and the surface nanocrystals.

[0062] The bottom layer is a transition layer. The core principle is that there is a gradient difference in mechanical properties between the surface nanocrystals and the heat sink matrix. The surface nanocrystals have high hardness and low plasticity, while the matrix has coarse grains with good toughness and moderate hardness. If they are directly connected, stress concentration at the interface will easily occur, causing the surface structure to crack and fall off under temperature changes or ultrasonic impact. As an intermediate structure connecting the surface layer and the matrix, the transition layer's mechanical properties (such as hardness and elastic modulus) gradually transition from the surface layer to the matrix, achieving a smooth transition from the surface nanocrystal structure to the matrix coarse grain structure and eliminating stress concentration caused by abrupt changes in properties.

[0063] The core function of the transition layer is to disperse the stress caused by temperature changes and ultrasonic stimulation, ensuring the strong bond between the gradient functional layer and the heat sink matrix. This prevents the surface functional layer from detaching or cracking during heat sink service, allowing the selective modification effect to be maintained long-term without diminishing with changing operating conditions. For example, if the pretreated billet is a diamond-copper matrix (matrix elastic modulus approximately 400 GPa) and the surface nanocrystal elastic modulus is approximately 500 GPa, then the elastic modulus of the transition layer gradually transitions from 480 GPa on the surface to 400 GPa on the matrix, with a thickness controlled at 20 μm. Through gradient ultrasonic energy input, a continuous transition in grain structure and mechanical properties is achieved, avoiding stress concentration. The transition layer is achieved by controlling the power gradient and duration gradient of the focused ultrasonic impact, constructing a 10-30 μm thick transition layer beneath the surface nanocrystals. Specifically, the ultrasonic impact power is gradually reduced from the surface to the substrate, while the duration of action is extended. This causes the grain structure of the transition layer to gradually transition from nanocrystals to micron-level coarse grains. Simultaneously, the mechanical properties transition from high hardness and high elastic modulus of the surface layer to low hardness and low elastic modulus of the substrate, ultimately forming a continuous performance gradient transition layer that ensures long-term stable bonding between the functional layer and the substrate.

[0064] In some specific embodiments, the frequency range of the full-band acoustic characteristic test covers the working frequency band of dual-frequency phase-locked ultrasonic standing wave. The test content includes the acoustic impedance, sound propagation velocity, sound attenuation coefficient, resonant frequency and phase response characteristics of the target heat sink. The test data are compared and analyzed with the acoustic characteristics of the pretreated billet to correct the acoustic characteristic deviation caused by selective modification, and to provide accurate measured data support for the construction of acoustic and thermal parameters.

[0065] The frequency range of the full-band acoustic characteristic test completely covers the entire operating frequency band of the dual-frequency phase-locked ultrasonic standing wave in the subsequent packaging process. Ultrasonic standing waves rely on the reflection and superposition of sound waves between multiple interfaces to form a stable waveform. Only by fully acquiring the acoustic response characteristics of the heat sink across the entire high and low dual-frequency operating range can the intrinsic characteristics of ultrasonic signal propagation, reflection, and interference be accurately determined. If the test frequency band is smaller than the actual control frequency band, the transmission variation of the dual-frequency signal cannot be fully captured, easily leading to problems such as standing wave drift, severe energy dissipation, and deviation of the interface antinodes from their bonding position, making stable and effective interface thermal resistance control impossible.

[0066] This test covers several core acoustic physics parameters, each with an independent and irreplaceable technical role. Acoustic impedance is used to determine the transmission and reflection ratio of the ultrasonic signal between the transducer and the heat sink, directly determining the impedance matching effect of the ultrasonic system. Sound propagation velocity is used to calculate the propagation period of the sound wave along the thickness of the heat sink, serving as the core calculation basis for accurately locating standing wave nodes and antinodes. The acoustic attenuation coefficient characterizes the magnitude of ultrasonic energy transmission loss within the heat sink, thereby determining the corresponding power compensation strategy. The resonant frequency corresponds to the inherent resonance characteristics of the heat sink; ensuring the control signal operates within the resonant range maximizes ultrasonic energy utilization efficiency. The phase response characteristics reflect the phase change pattern of the sound wave after passing through the heat sink, ensuring synchronous phase-locked interference of dual-frequency signals and forming a regular and stable interface standing wave.

[0067] After the tests were completed, the acoustic data of the target heat sink were compared and analyzed item by item with the original acoustic properties of the pretreated billet. After selective ultrasonic surface modification, the pretreated billet formed a gradient functional layer on the surface, and the grain arrangement, surface morphology, and internal stress state all underwent structural changes, resulting in a regular shift in the overall acoustic properties compared to the original billet. If the original acoustic parameters of the billet are continued to be used to formulate the control scheme, a series of problems will occur, such as discrepancies between theoretical and actual waveforms, disordered standing wave positions, and large deviations in thermal resistance monitoring conversion.

[0068] By comparing the acoustic data before and after modification, the acoustic characteristic shift caused by the selected modification can be accurately quantified, and the frequency reference, phase compensation value, power loss compensation coefficient, and standing wave wavelength calculation model can be corrected simultaneously. The corrected acoustic parameters perfectly match the actual physical state of the target heat sink, completely eliminating the deviation between theoretical and physical parameters caused by surface structure modification.

[0069] Verified and calibrated full-dimensional acoustic measurement data, combined with material mechanical properties and surface morphology defect detection results, jointly construct exclusive bound acoustic and thermal parameters. Precise acoustic laws can improve the intrinsic mapping relationship between ultrasonic control parameters and interface thermal resistance changes, making ultrasonic control initialization during the packaging stage more accurate, ensuring long-term stable contact of dual-frequency standing waves with the interface, achieving higher accuracy in in-situ monitoring and thermal resistance conversion, and making the dynamic parameter adaptive adjustment logic more in line with actual working conditions, thus comprehensively improving the consistency of interface thermal resistance control and long-term service stability.

[0070] In some specific embodiments, the dual-frequency phase-locked ultrasonic standing wave includes a first ultrasonic signal and a second ultrasonic signal with a frequency band lower than the first ultrasonic signal. The first ultrasonic signal is used to regulate the bulk thermal resistance of the interface material by breaking the agglomeration structure of the thermally conductive filler in the interface material through high-frequency shearing effect and guiding its directional arrangement. The second ultrasonic signal is used to regulate the interfacial contact thermal resistance by filling the microscopic air gaps at the interface through directional acoustic flow effect. The interface ultrasonic echo signal is acquired in real time by the phase-locked loop, and the phase difference between the incident wave and the reflected wave is compared to dynamically adjust the output phase of the first and second ultrasonic signals so that the antinode of the standing wave is always locked at the contact interface between the heat sink and the interface material. The dual-frequency ultrasonic control process is illustrated as follows. Figure 4 As shown.

[0071] Dual-frequency phase-locked ultrasonic standing waves are formed by the coupling and superposition of two sets of ultrasonic signals with different frequency bands. The first ultrasonic signal operates at a higher frequency, while the second ultrasonic signal operates at a lower frequency. The high and low frequencies work together without interfering with each other, and the superimposed waveforms form a stable standing wave field. This allows for targeted and specific control of the two root causes of thermal resistance at the interface, overcoming the technical shortcomings of single-frequency ultrasonic waves in addressing multiple thermal resistances.

[0072] High-frequency ultrasonic signals are used to improve the thermal conductivity of interface materials and reduce their bulk thermal resistance. Conventional encapsulation interface thermally conductive media are composite flexible thermally conductive materials, doped with a large amount of powdered thermally conductive fillers. During assembly, extrusion, and room-temperature settling, these fillers easily aggregate and form agglomerates. These agglomerates block continuous heat conduction channels, resulting in decreased thermal conductivity and persistently high bulk thermal resistance. High-frequency ultrasound generates high-frequency reciprocating microscopic shearing forces, which continuously break up the agglomerated filler structures through shearing effects. Simultaneously, the high-frequency vibration guides the dispersed fillers to align neatly along the heat conduction direction, constructing a continuous and smooth internal heat conduction network, significantly reducing inherent heat conduction losses from the material's structural level.

[0073] The low-frequency secondary ultrasonic signal is used to optimize the interface bonding contact state and reduce the interface contact thermal resistance. Low-frequency ultrasound can induce a directional micro-acoustic flow effect at the solid-solid interface. After the heat sink and interface material are bonded, surface micro-undulations, micropores, and tiny gaps will leave air gaps. Air has extremely low thermal conductivity and will form an insulating layer, drastically increasing the interface contact thermal resistance. The directional micro-acoustic flow can drive the flexible interface material to flow and fill all micro-gaps, expelling the trapped air at the interface and significantly increasing the effective bonding contact area between the heat sink and the interface material. The low-frequency vibration effect is gentle and does not disrupt the orderly arrangement of the filler structure of the high-frequency signal, complementing and synergizing with the high-frequency modulation.

[0074] The two sets of ultrasonic signals have a clear division of labor: the high frequency solves the internal thermal conductivity defects of the material, and the low frequency solves the interface bonding gap defects. They are superimposed and interfere to form a stable ultrasonic standing wave, which eliminates the overall thermal resistance of the interface in all directions.

[0075] A phase-locked loop (PLL) continuously acquires the ultrasonic echo signals reflected from the interface and compares the phase difference between the incident ultrasonic signal and the interface-reflected ultrasonic signal. Ultrasonic standing waves are essentially generated by the superposition and interference of the incident sound wave and the sound wave reflected from the interface. The position of the antinode with the strongest energy in the standing wave is entirely determined by the phase difference between the two sound waves. Changes in ambient temperature, thermal contraction at deep cryogenic temperatures, fluctuations in assembly stress, and material deformation can all alter the sound wave propagation speed and interface thickness, causing phase difference shifts and directly leading to the drift and misalignment of the standing wave antinodes.

[0076] The control system dynamically adjusts the output phase of the two ultrasonic signals based on the real-time phase difference, continuously compensating for phase deviations caused by changes in operating conditions, ensuring that the high-energy antinodes of the superimposed standing wave are always locked at the contact surface between the heat sink and the interface material. The intensity of the ultrasonic modulation effect is highly concentrated at the antinode position; only when the antinode is precisely positioned at the heat dissipation interface can the two modulation effects of high-frequency shearing and directional acoustic flow achieve optimal results. Once the antinode deviates from the target interface, the ultrasonic energy will be dispersed within the heat sink substrate or the encapsulation shell, not only causing thermal resistance modulation failure but also resulting in damage to the heat sink structure and accelerated aging of the interface material.

[0077] Full-process dynamic phase locking can adapt to drastic temperature change conditions, especially in deep cryogenic packaging scenarios where material shrinkage and deformation are significant and acoustic wave propagation characteristics fluctuate wildly. Real-time phase compensation can maintain the stability of the standing wave position for a long time, avoiding interface debonding, gap expansion, and abnormal surge in thermal resistance, ensuring stable and reliable thermal resistance control across the entire temperature range.

[0078] In some specific embodiments, the switching between dual-frequency phase-locked ultrasonic standing wave and in-situ monitoring of interface thermal resistance is achieved through the same ultrasonic actuator to realize time-division multiplexing. During the in-situ monitoring of interface thermal resistance, the collected ultrasonic echo signal is converted into real-time interface thermal resistance data through the acoustic-thermal parameter model, and the body thermal resistance component and contact thermal resistance component of the interface thermal resistance are monitored simultaneously.

[0079] The integrated time-division multiplexing operation mechanism of ultrasonic standing wave control and in-situ monitoring of interface thermal resistance adopts a single ultrasonic actuator to simultaneously undertake the dual functions of ultrasonic signal transmission and interface echo reception. While simplifying the device structure, it ensures a high degree of homogeneity between control and monitoring. It is the core technical support for the accurate feedback and dynamic adaptive adjustment of the entire closed-loop thermal resistance control.

[0080] The same ultrasonic actuator switches its operating state at high speed according to a preset time sequence, alternately performing dual-frequency phase-locked ultrasonic standing wave modulation and interface thermal resistance non-destructive monitoring. During the modulation period, the actuator outputs dual-frequency ultrasonic signals and forms a stable standing wave, which continuously acts on the heat sink interface to optimize thermal resistance. During the monitoring interval, the actuator quickly switches to signal acquisition mode to receive the reflected echo from the interface. The time interval between these alternations is extremely short, ensuring that the stable standing wave shape is not disrupted and the overall thermal resistance modulation process is not interrupted.

[0081] Sharing a single ultrasonic actuator unit can eliminate detection errors at their source. Control and monitoring share a completely consistent sound wave propagation path, interface coupling position, and acoustic response benchmark, eliminating installation deviations, differences in sound wave loss, and waveform phase shifts that can occur with two independent devices. Under extreme temperature variations and conditions of deep and low temperatures, where material shrinkage and deformation are significant, the same-source monitoring mode can maintain a consistent sound wave propagation pattern, greatly improving the accuracy of interface thermal resistance calculations.

[0082] The acquired ultrasonic echo signals are imported into a dedicated acoustic-thermal parameter model for quantization. The acoustic-thermal parameter model pre-establishes a one-to-one correspondence between ultrasonic wave characteristics and interface thermal resistance. Based on data such as echo amplitude attenuation, phase change difference, sound wave propagation time, and interface reflection characteristics, the current real-time interface thermal resistance value is directly calculated. This achieves non-invasive online real-time detection without the need for additional contact temperature or heat measurement elements.

[0083] The monitoring process can simultaneously distinguish and analyze the bulk thermal resistance component and the contact thermal resistance component of the interface. High-frequency ultrasonic correlation echo characteristics correspond to the dispersion and arrangement of fillers within the interface material, thereby determining the bulk thermal resistance corresponding to the thermal conductivity of the interface material itself. Low-frequency ultrasonic correlation echo characteristics correspond to the size of the interface bonding gap and changes in the effective contact area, thereby determining the contact thermal resistance caused by the interface bonding gap.

[0084] Two types of thermal resistance components are monitored and fed back independently, allowing for more targeted parameter adjustments. When the body thermal resistance is abnormal, the system automatically adjusts the high-frequency ultrasonic signal parameters; when the contact thermal resistance is abnormal, the system automatically adjusts the low-frequency ultrasonic signal parameters, forming a layered, precise closed-loop adjustment. The system operates continuously in a time-division multiplexing cycle, providing real-time feedback on thermal resistance changes until the interface thermal resistance stabilizes and meets the standards, providing a reliable basis for subsequent ultrasonic signal output for finalization.

[0085] In some embodiments, the shaping ultrasonic signal is a low-power narrowband ultrasonic signal, whose frequency band matches the resonant frequency of the target heat sink. The output power and duration of action are dynamically determined based on acoustic-thermal parameters and the target interface thermal resistance. Its core function is to fix the microstructure of the gradient functional layer on the surface of the target heat sink and the filler arrangement of the interface material, suppressing the rebound of interface thermal resistance during subsequent encapsulation, curing, and service, and ensuring the long-term stability of interface thermal resistance. The shaping ultrasonic signal uses a low-power narrowband ultrasonic signal with a pure waveform free of stray harmonics, which will not disturb the already formed ordered microstructure of the interface. The signal operating frequency band matches the inherent resonant frequency of the target heat sink, enabling efficient structural coupling with minimal energy, and completing structural curing without damaging the substrate and interface material. The output power and duration of the shaping ultrasonic signal are not fixed process values ​​but dynamically matched with specific acoustic-thermal parameters and the actual stable state of the interface thermal resistance. The initial dual-frequency ultrasonic treatment has already optimized the filler arrangement and filled interface gaps, reducing the interface thermal resistance to the ideal range. However, the heating during encapsulation and curing, long-term temperature cycling, and structural stress relaxation can all cause the microstructure to rebound and loosen, resulting in a rebound increase in interface thermal resistance. Ultrasonic shaping, through gentle and continuous steady-state vibration, fixes the grain morphology and texture arrangement of the gradient functional layer on the surface of the heat sink, while simultaneously locking the directional distribution of the thermally conductive filler within the interface material. This solidifies the optimal bonding structure and thermally conductive microchannels at the interface, suppressing structural shifts caused by subsequent process stress and service temperature changes, maintaining a low thermal resistance interface state over the long term, and ensuring stable and reliable heat dissipation performance throughout the device's entire lifecycle.

[0086] In some embodiments, when the target operating temperature range is a deep cryogenic range, the mechanical and acoustic properties of the pre-treated billet are temperature-dependent parameters within the deep cryogenic range. The temperature-dependent compensation module for acoustic and thermal parameters further introduces a deep cryogenic thermal shrinkage coefficient correction term. During the cooling process after pre-assembly, the ultrasonic control system collects interface temperature data in real time and dynamically adjusts the output parameters of the dual-frequency ultrasonic signal based on the acoustic and thermal parameters to compensate for the nonlinear changes in the acoustic and thermal expansion properties of the material under deep cryogenic conditions, thus avoiding a nonlinear spike in interface thermal resistance. A comprehensive temperature-dependent parameter adaptation mechanism is improved for the special working conditions of deep cryogenic conditions. Under deep cryogenic conditions, various packaging materials will experience uneven nonlinear shrinkage. The mechanical strength and thermal expansion law of the heat sink change drastically with temperature, and the sound wave propagation speed, acoustic impedance, and phase characteristics also show nonlinear shifts. Using room-temperature material parameters for ultrasonic control will cause standing wave shift, energy coupling failure, and increased interface debonding gaps, ultimately leading to an uncontrolled and rapid spike in interface thermal resistance. Therefore, under deep cryogenic conditions, the complete and continuous temperature-dependent mechanical and acoustic properties of the pre-treated billet within the low-temperature range are directly detected. Simultaneously, a temperature change compensation module is added to the acoustic-thermal parameter system, along with an additional correction coefficient specifically for deep-temperature thermal shrinkage. Throughout the device cooling process, the system collects interface temperature data in real time and dynamically adjusts various output parameters of the dual-frequency ultrasound in sync with the temperature change characteristic curve. This real-time compensation for changes in the acoustic and thermal expansion properties of the materials caused by low temperatures stabilizes the position of the standing wave, maintains a tight interface fit, and fundamentally prevents interface delamination and void expansion caused by deep-temperature deformation, thus completely solving the industry problem of uncontrolled nonlinear increase in thermal resistance at the interface of deep-temperature packaging.

[0087] In some embodiments, acoustic-thermal parameters can be adaptively updated based on real-time monitoring data during the interface thermal resistance adjustment process. The updated acoustic-thermal parameters are re-bound to the unique identifier of the target heat sink, forming a parameter iteration file specific to that target heat sink. This provides a benchmark reference for the construction of acoustic-thermal parameters for subsequent heat sinks of the same type, and also provides parameter support for the maintenance and adjustment of interface thermal resistance during the device's service life. The actual interface thermal resistance adjustment process generates a large amount of real-world operating condition feedback data. This data can continuously calibrate and optimize the initial theoretical acoustic-thermal parameters, correcting the deviation between model calculations and actual physical characteristics, making the correspondence between ultrasonic parameters and thermal resistance more accurate. The optimized and updated acoustic-thermal parameters are re-bound and stored with the unique identifier of the target heat sink, forming a parameter iteration file specific to each heat sink. This file can be reused for the processing of subsequent heat sinks of the same batch and type, significantly shortening the calibration and debugging cycle of new heat sinks and improving batch production consistency and processing efficiency. Meanwhile, the archives are stored for long-term use. After the device is installed and put into service, the parameters can be directly retrieved to carry out online non-destructive thermal resistance monitoring and maintenance control. The interface thermal resistance that increases due to aging can be repaired without disassembling the package, thus fully opening up the entire heat dissipation control chain from heat sink manufacturing, packaging assembly, to post-maintenance operation and maintenance.

[0088] In some embodiments, the preset target threshold is determined based on a comprehensive consideration of the target operating temperature range, device heat dissipation requirements, and interface material characteristics. The target threshold can be dynamically adjusted according to the actual packaging scenario. After the interface thermal resistance reaches the target threshold, multiple sets of cyclic monitoring and parameter fine-tuning are performed to ensure that the fluctuation range of the interface thermal resistance is ≤8%, and the duration of thermal resistance stability is not less than the preset duration, before finalization and control are completed. The target threshold for interface thermal resistance is not uniformly fixed; it is determined comprehensively based on the operating temperature range, device heat dissipation power level, and the thermal conductivity of the interface material itself, and can be flexibly adjusted according to different packaging scenarios. A single pass of the interface thermal resistance test does not represent the completion of the process; the system will perform multiple rounds of cyclic intermittent monitoring and fine-tuning of parameters. Strict control is maintained to ensure that the fluctuation range of the interface thermal resistance does not exceed 8%, while requiring the low thermal resistance state to continuously meet the preset duration. This judgment method can effectively avoid instantaneous false compliance and prevent the thermal resistance from rising later due to slow relaxation of material stress and gradual changes in microstructure. Multiple cyclic verifications ensure long-term stable heat dissipation of the packaged product, significantly improving the reliability of high-power precision device packaging and meeting the requirements for long-life stable operation under harsh conditions.

[0089] A packaged heat sink thermal resistance control system based on ultrasonic standing waves includes: Pretreatment unit 1 is used to obtain heat sink blanks. First, the heat sink blanks are subjected to ultrasonic impact treatment over the entire area to eliminate internal residual stress, and then dimensional stability treatment is performed to obtain pretreated blanks. The target heat sink unit 2 is used to detect surface defects in the pretreated billet. Based on the defect detection results and the material mechanical and acoustic properties of the pretreated billet in the target working temperature range, the output parameters of focused ultrasonic impact are matched to perform selective area modification treatment on the pretreated billet to obtain the target heat sink. Acoustic-thermal parameter unit 3 is used to test the acoustic properties of the target heat sink across the entire frequency band. It combines the material's mechanical properties with acoustic properties, morphology and defect detection results to construct acoustic-thermal parameters that are bound to the target heat sink. The ultrasonic testing unit 4 is used to perform dual-frequency phase-locked ultrasonic standing wave and interface thermal resistance in situ monitoring of the target heat sink based on acoustic and thermal parameters after the target heat sink is pre-assembled with the interface material and the encapsulation substrate. The thermal resistance control unit 5 is used to dynamically adjust the parameters of the ultrasonic control system based on real-time monitored interface thermal resistance data and acoustic-thermal parameters until the interface thermal resistance reaches the preset target threshold. It then outputs a shaping ultrasonic signal to shape the target heat sink and interface material, thus completing the interface thermal resistance control.

[0090] Those skilled in the art will understand that the components of this application described above can be implemented using general-purpose computing systems. They can be centralized on a single computing system or distributed across a network of multiple computing systems. Optionally, they can be implemented using computer-executable program code, thereby allowing them to be stored in a storage system for execution by the computing system. Alternatively, they can be fabricated as separate integrated circuit components, or multiple components or steps can be fabricated as a single integrated circuit component. Thus, this application is not limited to any particular combination of hardware and software.

[0091] Note that the above description is merely a preferred embodiment and the technical principles employed in this application. Those skilled in the art will understand that this application is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of this application. Therefore, although this application has been described in detail through the above embodiments, this application is not limited to the above embodiments. Many other equivalent embodiments may be included without departing from the concept of this application, and the scope of this application is determined by the scope of the appended claims.

[0092] The above disclosures are only a few specific implementation scenarios of this application. However, this application is not limited to these. Any variations that can be conceived by those skilled in the art should fall within the protection scope of this application.

Claims

1. A method for controlling the thermal resistance of a packaged heat sink based on ultrasonic standing waves, characterized in that, include: To obtain the heat sink blank, the heat sink blank is first subjected to ultrasonic impact treatment over its entire surface to eliminate residual internal stress, and then dimensional stability treatment is performed to obtain the pretreated blank. The surface defect detection is performed on the pretreated billet. Based on the defect detection results and the material mechanical and acoustic properties of the pretreated billet in the target working temperature range, the output parameters of focused ultrasonic impact are matched to perform selective area modification treatment on the pretreated billet to obtain the target heat sink. The target heat sink is subjected to full-band acoustic property testing. Based on the material's mechanical and acoustic properties, morphology and defect detection results, acoustic and thermal parameters bound to the target heat sink are constructed. After the target heat sink is pre-assembled with the interface material and the encapsulation substrate, the target heat sink is monitored in situ using a dual-frequency phase-locked ultrasonic standing wave and interface thermal resistance based on the acoustic and thermal parameters. Based on real-time monitoring of interface thermal resistance data and the aforementioned acoustic and thermal parameters, the parameters of the ultrasonic control system are dynamically adjusted until the interface thermal resistance reaches the preset target threshold. Then, a shaping ultrasonic signal is output to shape the target heat sink and interface material, thus completing the interface thermal resistance control.

2. The method for controlling the thermal resistance of a packaged heat sink according to claim 1, characterized in that, The ultrasonic shock full-domain processing specifically includes: adopting a dual-band ultrasonic synergistic shock mode, and pre-setting two ultrasonic shock signals of different frequency bands based on the material characteristics of the heat sink billet. One frequency band of ultrasound is used to peel off and release the deep residual internal stress inside the billet, and the other frequency band of ultrasound is used to eliminate the residual internal stress on the surface of the billet and to preliminarily optimize the surface microstructure.

3. The method for controlling the thermal resistance of a packaged heat sink according to claim 1, characterized in that, In the surface defect detection, macroscopic and microscopic defect parameters of the pretreated blank surface are acquired simultaneously. The macroscopic defect parameters include defect location, defect size, defect depth and defect distribution density. The microscopic defect parameters include surface roughness, microcrack size, machining residual stress distribution and surface grain distortion degree.

4. The method for controlling the thermal resistance of a packaged heat sink according to claim 1, characterized in that, The output parameters of the focused ultrasound shock include shock frequency band, focused power, shock amplitude, scanning path, and duration of action.

5. The method for controlling the thermal resistance of a packaged heat sink according to claim 4, characterized in that, If the surface defect detection results show that the larger the size and the deeper the defect, the corresponding focusing power and impact amplitude will increase in a stepwise manner; if the surface defect detection results show that the micro-roughness is higher and the residual stress is more concentrated, the corresponding impact frequency band and action time will be dynamically adjusted.

6. The method for controlling the thermal resistance of a packaged heat sink according to claim 1, characterized in that, The selective modification process includes forming a gradient functional layer on the surface of the pretreated billet. The gradient functional layer is distributed in a gradient from the surface layer to the substrate. The surface layer has a nanocrystalline structure to match the thermal expansion coefficient of the interface material, the middle layer has a micro-nano textured structure to improve the spreadability and anchoring effect of the interface material, and the bottom layer is a transition layer to achieve a smooth connection between the mechanical properties of the surface layer and the substrate.

7. The method for controlling the thermal resistance of a packaged heat sink according to claim 1, characterized in that, The frequency range of the full-band acoustic characteristic test covers the working frequency band of dual-frequency phase-locked ultrasonic standing wave. The test content includes the acoustic impedance, sound propagation velocity, sound attenuation coefficient, resonant frequency and phase response characteristics of the target heat sink. The test data are compared and analyzed with the acoustic characteristics of the pretreated billet to correct the acoustic characteristic deviation caused by selective area modification, and to provide accurate measured data support for the construction of acoustic and thermal parameters.

8. The method for controlling the thermal resistance of a packaged heat sink according to claim 7, characterized in that, The dual-frequency phase-locked ultrasonic standing wave includes a first ultrasonic signal and a second ultrasonic signal with a frequency band lower than the first ultrasonic signal. The first ultrasonic signal is used to regulate the bulk thermal resistance of the interface material, breaking the agglomeration structure of the thermally conductive filler in the interface material through high-frequency shearing effect and guiding its directional arrangement. The second ultrasonic signal is used to regulate the interface contact thermal resistance, filling the microscopic air gap of the interface through directional acoustic flow effect. The interface ultrasonic echo signal is collected in real time by the phase-locked loop, and the phase difference between the incident wave and the reflected wave is compared to dynamically adjust the output phase of the first ultrasonic signal and the second ultrasonic signal, so that the antinode of the standing wave is always locked at the contact interface between the heat sink and the interface material.

9. The method for controlling the thermal resistance of a packaged heat sink according to claim 1, characterized in that, The switching between dual-frequency phase-locked ultrasonic standing wave and in-situ monitoring of interface thermal resistance is achieved by using the same ultrasonic actuator to realize time-division multiplexing. During the in-situ monitoring of interface thermal resistance, the collected ultrasonic echo signal is converted into real-time interface thermal resistance data through the acoustic-thermal parameter model, and the body thermal resistance component and contact thermal resistance component of the interface thermal resistance are monitored simultaneously.

10. A packaged heat sink thermal resistance control system based on ultrasonic standing waves, characterized in that, include: The pretreatment unit is used to obtain the heat sink blank. First, the heat sink blank is subjected to ultrasonic impact treatment over its entire area to eliminate internal residual stress, and then dimensional stability treatment is performed to obtain the pretreated blank. The target heat sink unit is used to detect surface defects in the pretreated blank. Based on the defect detection results and the material mechanical and acoustic properties of the pretreated blank in the target working temperature range, the output parameters of focused ultrasonic impact are matched to perform selective modification treatment on the pretreated blank to obtain the target heat sink. The acoustic-thermal parameter unit is used to perform full-band acoustic characteristic testing on the target heat sink, and to construct acoustic-thermal parameters bound to the target heat sink by combining the material's mechanical and acoustic properties, morphology and defect detection results. An ultrasonic testing unit is used to perform dual-frequency phase-locked ultrasonic standing wave and in-situ monitoring of interface thermal resistance of the target heat sink based on the acoustic and thermal parameters after the target heat sink is pre-assembled with the interface material and the encapsulation substrate and the ultrasonic control system. The thermal resistance control unit is used to dynamically adjust the parameters of the ultrasonic control system based on the real-time monitored interface thermal resistance data and the acoustic-thermal parameters until the interface thermal resistance reaches the preset target threshold. It then outputs a shaping ultrasonic signal to shape the target heat sink and interface material, thus completing the interface thermal resistance control.

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