A real-time monitoring device for thermal fatigue performance of diamond-copper composite material and a use method thereof

Abstract

The patent relates to the field of microelectronics, and particularly to a device and method for real-time monitoring of thermal fatigue performance of diamond-copper composite materials through a thermal fatigue-resistivity correlation mechanism. The present application is based on the thermal fatigue-resistivity correlation mechanism of diamond-copper composite materials, and through the construction of a high-thermal-conductivity insulation bearing system, a precise temperature change control system and a high-precision resistance test system, real-time, accurate and stable monitoring of the thermal fatigue performance of diamond-copper composite materials is achieved. The present application provides a new technical means for the thermal fatigue failure warning and mechanism research of diamond-copper composite materials for high-power electronic devices.

Description

Technical Field

[0001] This patent relates to the field of microelectronics, and in particular to a device and method for real-time monitoring of the thermal fatigue performance of diamond-copper composite materials through a thermal fatigue-resistivity correlation mechanism. Background Technology

[0002] With the continuous improvement of the integration and power density of high-power electronic devices, the demand for thermal management in fields such as microelectronics, aerospace, rail transportation, electrical engineering, and national defense has increased significantly. Against this backdrop, traditional thermal management materials (such as metals and ceramics) are insufficient to maintain the safety and reliability of high-power devices; therefore, the development of thermal management materials with excellent thermal properties is crucial. Diamond composite materials, with their significant advantages of ultra-high thermal conductivity and low coefficient of thermal expansion, show great promise for heat dissipation in high-power electronic devices. However, limitations such as poor wettability at the heterogeneous interface between diamond and metal, and low thermal property matching, still pose many challenges to their overall performance and industrialization process.

[0003] One of the biggest challenges facing diamond-copper composites in high-power electronic devices subjected to frequent thermal cycling is thermal fatigue damage caused by interfacial thermal stress. Diamond and copper exhibit numerous performance mismatches, including but not limited to their extremely poor chemical affinity (they are mutually insoluble and do not react chemically), and a difference of an order of magnitude in their coefficients of thermal expansion. During the temperature cycling process of preparation and use, this mismatch generates periodic, significant thermal stress at the interface, leading to a gradual increase in the density of crystal defects in the copper matrix, resulting in an increase in resistivity and a gradual decrease in thermal conductivity. With increasing thermal cycling, the emergence of localized stress concentrations can induce microcracks at the interface. The appearance and propagation of these microcracks significantly increase interfacial thermal resistance, leading to a decrease in the overall thermal conductivity of the material and severely impacting the lifespan of high-power electronic devices.

[0004] Previous studies on the thermal fatigue performance of diamond-copper composites have largely focused on process improvements and simple performance characterization optimizations. These methods primarily involve improving interfacial bonding by forming a transition layer at the interface, or reducing sintering temperature and increasing sintering pressure to decrease internal stress caused by thermal mismatch and thus reduce the number of microcracks, effectively optimizing the material's thermal conductivity and thermal fatigue performance. However, these traditional methods for optimizing thermal fatigue performance are characterized by significant trial-and-error, failing to monitor and analyze the material's microstructure and the evolution of microcracks at each stage of thermal fatigue in real time, and thus unable to perform targeted optimizations to achieve precise control over the composite material's thermal fatigue performance.

[0005] Currently, there are few reports on in-situ monitoring of the thermal fatigue performance of diamond composite materials. Due to the lack of real-time, dynamic monitoring of thermal fatigue damage, existing results are fragmented and fail to effectively integrate perspectives from multiple disciplines such as thermodynamics, mechanics, electricity, and materials science. This makes it difficult to fully reveal the intrinsic mechanisms of damage initiation and propagation, thus hindering the synergistic design of interface structures that combine high thermal conductivity and high thermal fatigue performance. Furthermore, a search revealed that there is no dedicated real-time monitoring device for the thermal fatigue performance of diamond-copper composite materials for high-power devices, and no specific methods for using such devices are discussed.

[0006] Therefore, seeking a device and its application method that can realize real-time dynamic monitoring of the thermal fatigue state of materials during thermal cycling, and deeply revealing the damage mechanism of the interface in the thermal fatigue process and establishing a corresponding systematic theoretical model are key measures to promote the development of diamond composite materials. Summary of the Invention

[0007] Research has found that the increase in interfacial thermal resistance and the change in macroscopic material resistance are essentially of the same origin, both stemming from the intensified carrier scattering caused by interfacial damage. Specifically, in diamond-copper composites, an unavoidable increase in resistivity occurs during thermal fatigue. At different stages of this process, the density of crystal defects induced by thermal stress gradually increases in the copper matrix, resulting in characteristic resistivity response patterns at each stage. Therefore, by establishing an in-situ resistivity monitoring system for devices under actual service conditions, real-time dynamic monitoring of the thermal fatigue state of diamond-copper composites can be achieved using resistivity evolution curves and characteristic parameters, providing key technical support for early warning of thermal fatigue failure in high-power electronic heat dissipation devices. Based on existing research and searches, this patent innovatively proposes a device and method for real-time monitoring of the thermal fatigue performance of diamond-copper composites. This invention utilizes the resistivity changes of diamond-copper composites during thermal cycling to develop an in-situ, real-time, accurate, and stable monitoring method for thermal fatigue. In actual service, this allows for timely feedback on the material's usage status, providing safety assurance; and, through monitoring, it allows for feedback on the causes of thermal fatigue failure in diamond-copper composites, enabling targeted optimization. This enables real-time dynamic monitoring of the thermal fatigue state of diamond-copper composite materials under service conditions, aiding in the study of deeper mechanisms and representing a breakthrough in the in-depth mechanism analysis of material thermal management.

[0008] This invention aims to solve the technical challenge of the "invisible" performance evolution of diamond-copper composites during service by establishing a novel in-situ monitoring system based on resistivity response for thermal fatigue of diamond-copper composites. Utilizing the thermal fatigue-resistivity correlation mechanism, thermal cycling is achieved through heating and air cooling equipment, while resistance and temperature are measured using a resistivity meter and a thermometer. The resistivity is calculated based on the geometric dimensions of the test sample, and the system is controlled by a computer to record changes in material temperature and resistivity data, thus studying the relationship between resistivity and thermal fatigue performance. This invention constructs a thermal fatigue performance monitoring method to meet the need for real-time monitoring of changes in the thermal fatigue performance of diamond-copper composites.

[0009] This invention discloses a real-time monitoring device for the thermal fatigue properties of diamond-copper composite materials, comprising a resistance meter, a heating stage, a sample support stage, a flow channel cover, an air supply device, an anemometer, a specially made circular copper patch, a first set of temperature measuring devices, a second set of temperature measuring devices, and a data collection and analysis device.

[0010] The resistance meter is connected to the end face of the cylindrical sample to be tested via a wire with a specially designed circular copper patch at the end. The cylindrical sample to be tested is placed horizontally on the sample support stage. The sample support stage has an air duct and a sample support position. The sample support position is a recessed semi-cylindrical hole, and the sample support position and the cylindrical sample to be tested form a clearance fit. The first set of temperature measuring devices includes three temperature measuring probes. The first temperature measuring probe is set on the top of the flow channel cover and perpendicular to the sample support position, with the measuring point aligned with the geometric center of the sample. This probe is defined as probe A. The second temperature measuring probe is located to the left of probe A, with the measuring point aligned with the axial center of the left end face of the sample. This probe is defined as probe B. The third temperature measuring probe is located to the right of probe A, with the measuring point aligned with the axial center of the right end face of the sample. This probe is defined as probe C. The second set of temperature measuring devices is set on the flow channel cover and faces the sample support stage to collect the temperature data of the sample support stage. This probe is defined as probe D.

[0011] The thermal conductivity of the sample support stage is greater than 150 W / m·K; the sample support stage is set on the heating stage, the anemometer is set on the top of the flow channel cover, and the air supply device is set on the side of the flow channel cover close to the anemometer.

[0012] The anemometer, the first set of temperature measuring devices, and the second set of temperature measuring devices are connected to the data collection and analysis device via wires.

[0013] The specially designed circular copper patch is connected to the end face of the cylindrical sample to be tested. The specially designed circular copper patch is a preheated circular copper patch, wherein the preheating treatment is performed on the surface of the pure copper sample in a high-precision resistance furnace at a specific temperature and holding time; the preheating temperature must be higher than the maximum test temperature. Preferably, the specially designed circular copper patch is connected to the end face of the sample to be tested, and the specially designed circular copper patch is a preheated circular copper patch. The preheating treatment is performed on the surface of the pure copper sample in a high-precision resistance furnace at a specific temperature and holding time, with a pretreatment temperature of 130~230℃, and the pretreatment environment contains oxygen, with an oxygen volume percentage of less than or equal to 21%. For the widest temperature range, a specially designed circular copper patch with an oxide film thickness of 0.9 μm to 1.1 μm is selected. Preferably, when applied to a maximum test temperature of 151-200°C, the recommended thickness of the oxide film on the surface of the specially made circular copper patch is 0.9 μm-1.1 μm; when the maximum test temperature is 101-150°C, the recommended thickness is 0.5 μm-0.7 μm; and when the maximum test temperature is less than or equal to 100°C, the recommended thickness is 140 nm-160 nm. In this invention, the pretreatment temperature is higher than the maximum test temperature.

[0014] This invention discloses a real-time monitoring device for the thermal fatigue properties of diamond-copper composite materials, wherein an air duct is provided on the upper surface of the sample support stage. This air duct allows for rapid heat dissipation between the heating stage and the sample support stage during sample cooling, thereby promoting sample cooling.

[0015] This invention discloses a real-time monitoring device for the thermal fatigue properties of diamond-copper composite materials. A specially designed circular copper patch with a stable surface oxide film is prepared using a heat treatment process. The application of this copper patch reduces sample micro-vibrations, eliminates dynamic shifts in resistance data, and reduces measurement errors in sample resistance. The thickness of the circular copper patch is 2-2.5 mm, and the contact area between a single specially designed circular copper patch and one end of the sample under test is greater than 100 mm². 2 Preferably 100~150 mm 2 The copper patch is in close contact with the sample. In practical applications, the copper patch and the sample are assembled using a stable mechanical contact method.

[0016] This invention discloses a real-time monitoring device for the thermal fatigue properties of diamond-copper composite materials. An acrylic sheet is used to prepare a flow channel cover for visualization. An opening is made at the top of the flow channel cover for mounting an anemometer and a temperature probe, and the opening is sealed.

[0017] Preferably, the sample support stage is made of processable insulating materials such as AlN and SiC. AlN has a thermal conductivity of 170-230 W / m·K at room temperature; 3C-SiC has a thermal conductivity of approximately 500 W / m·K, 4H-SiC approximately 350 W / m·K, and 6H-SiC approximately 320 W / m·K at room temperature, ensuring efficient heat transfer while maintaining insulation within the heating stage.

[0018] The upper surface of the sample support stage (i.e. the surface where the sample support position is located) is provided with an air duct groove A; the two ends of the sample support position face the air duct groove B, and the air duct groove B is located on the upper surface of the sample support stage.

[0019] The depth of air duct A is 2-4 mm, preferably 3 mm; its length is equal to the length of the sample support stage; the width of air duct A is 5-8 mm, preferably 6 mm, and the number of air ducts A is greater than or equal to 2. As a further preferred embodiment, the spacing between adjacent air ducts A is equal, and the dimensions of adjacent air ducts A are the same.

[0020] As a further preferred option, the sample bearing position and the air duct groove B have overlapping parts.

[0021] The depth of the air duct B is 2-4 mm, preferably 3 mm; the width of the air duct B is 5-8 mm, preferably 6 mm. Its length is equal to the length of the sample support stage.

[0022] The sample support area is a recessed semi-cylindrical shape with a length of 1.0 to 1.1 times (height of cylindrical sample + 2 × thickness of copper patch); the diameter of the sample support area is 1 to 1.1 times the diameter of the cylindrical sample.

[0023] The ceramic insulating plate (sample support stage) has sample support positions and air duct grooves, such as... Figure 2 As shown, the depth of the two grooves is less than the thickness of the ceramic plate. The diameter of the sample support position is 1 to 1.1 times the diameter of the cylindrical sample. This design prevents the sample from being blown away or flying during air cooling, ensuring the accuracy and stability of resistance measurement. The air duct grooves increase the area of ​​the sample support stage exposed to cold air, improving its heat dissipation rate and uniformity. In addition, the air duct groove B connected to the sample support position can also be used to place the resistance meter's wires, ensuring a smooth connection between the wires and both ends of the sample, avoiding resistance measurement errors caused by wire vibration. In particular, an embedded structure is provided below the sample support stage to achieve mechanical assembly with the heating stage below.

[0024] The present invention discloses a method for using a real-time monitoring device for the thermal fatigue properties of diamond-copper composite materials, comprising the following steps:

[0025] (1) Sample pretreatment: The diamond-copper composite cylindrical sample was subjected to surface oxide layer grinding (light grinding with 400 grit sandpaper), alcohol ultrasonic cleaning (10 min), hot air drying (50℃, 5 min), and gold spraying treatment in sequence to ensure that the sample surface is free of oil, impurities and oxide film, so as to avoid affecting the accuracy of resistance test.

[0026] (2) Experimental preparation and system assembly: The pretreated cylindrical sample is placed horizontally (i.e., the axial direction of the sample is parallel to the length direction of the air duct groove A on the sample support platform) into the sample support position of the sample support platform. The resistance meter wire is fixed through the line groove (air duct groove B) to ensure a stable connection between the sample and the specially made circular copper patch at the end of the resistance meter wire. The sample support platform with the sample is embedded in the middle position of the heating platform of the customized heating equipment (positioning deviation ≤ 1 mm). An external flow channel cover with openings at both ends is installed as a flow channel. The anemometer is placed inside the flow channel cover 5 cm away from the sample. The air supply device (air volume ≥ 50 m³ / h) is installed at the air inlet on the right side of the flow channel. The probe of infrared thermometer A is set on the top of the flow channel cover and perpendicular to the sample support position. The temperature measurement point is aligned with the geometric center of the sample, and the temperature measurement distance is set to 10 cm. The temperature measurement point of the probe of infrared thermometer B is aligned with the axial center of the left end face of the sample and is 3 cm away from probe A. The temperature measurement distance is set to 10-11cm; the probe of infrared thermometer C is aligned with the axial center of the right end face of the sample, 3cm away from probe A, and the temperature measurement distance is set to 10-11cm; the probe of infrared thermometer D is directly facing the sample support stage, 3cm away from probe A, and is used to measure the temperature of the sample support stage.

[0027] (3) Instrument startup: Start the equipment in the order of “infrared thermometer → anemometer → resistance meter → computer integrated system”, set the resistance meter sampling frequency to 20Hz, the infrared thermometer temperature measurement accuracy to ±0.5℃, and the computer system to start the data synchronous acquisition mode.

[0028] (4) Preheating and Cyclic Verification: Heat the sample stage to 80℃ at a rate of 10K / min~20K / min and hold for 10min (ensure uniform overall sample temperature with a temperature difference ≤2℃); then turn off the heating equipment and cool it down to room temperature (25℃±2℃) by air cooling. Monitor the sample temperature change in real time (infrared thermometer monitors the sample surface, temperature difference must be ≤3℃) and the fluctuation of heating / cooling rate (fluctuation range ≤±1K / min); check whether the resistance meter data is stable (no jumps, values ​​within ±5% of the theoretical resistance value of the sample at room temperature); if there are abnormal data such as uneven temperature, excessive / increased resistance, or resistance not changing with temperature, the sample installation position needs to be readjusted or the wires replaced.

[0029] (5) Heating stage: The computer system issues an instruction, and the heating equipment heats the sample to 150~200℃ (±1℃) at a rate of 10K / min~20K / min, and holds it for 5~10min (selected according to the sample size, 8min is preferred for Φ10mm×15mm samples); the temperature data is fed back in real time during the heating process. If the temperature exceeds the set temperature by ≥10℃ (if the temperature exceeds the set temperature by ≥10℃ means that the average temperature of the three temperature probes A, B and C exceeds the set temperature by more than 10 degrees Celsius), the system will automatically trigger the heating pause protection.

[0030] (6) Cooling stage: The heating equipment is automatically shut down and the air supply device is immediately started. The cooling rate is controlled by adjusting the wind speed (10~15m / s) through the computer to be 15K / min~25K / min. After cooling down to 10℃ (±1℃), the temperature is maintained for 2~5min (preferably 3min to avoid the sample being too cold). During the cooling process, the anemometer monitors the airflow stability in real time, and the fluctuation range is ≤±0.5m / s.

[0031] (7) Room temperature transition stage: Reduce the air supply speed to 5m / s and allow the sample temperature to slowly rise to room temperature (25℃±2℃), and keep it warm for 2~5min (preferably 4min); before the end of the transition stage, record the initial stable value of the sample resistance as a reference for subsequent comparison.

[0032] (8) Real-time data acquisition: The resistivity meter records the instantaneous resistance value of the sample and automatically saves it to the specified folder (name format: "date-sample number-number of cycles"); the computer system automatically calculates the resistivity according to the formula "resistivity = resistance × cross-sectional area / length" (the actual size parameters of the sample need to be entered in advance); the sample temperature data collected by the infrared thermometer and the real-time wind speed data of the anemometer are recorded simultaneously, and the time of the three is accurately aligned (error ≤ 0.1s).

[0033] (9) Data anomaly handling: If a set of data shows a jump (such as a sudden change in resistance value ≥10%), immediately pause the cycle, check whether the sample has cracked, debonded or other phenomena, and after troubleshooting, re-execute the cycle and mark "retest" in the data record.

[0034] (10) Cyclic execution: Repeat the “thermal cycle core execution” and “data acquisition” steps, and set the number of cycles to 400~700 times (adjust according to test requirements; if used for failure mechanism analysis, it is recommended to take 600 times to cover the complete fatigue stage); pause for 5 minutes after every 100 cycles, check the appearance of the sample and the connection status of the equipment to ensure the continuity of the test.

[0035] (11) Results analysis: Plot the "resistivity-cycle number" evolution curve and extract characteristic parameters.

[0036] (12) Performance judgment: Divide the thermal fatigue stage according to the curve trend (initial stable stage: resistivity fluctuation ≤2%; fatigue development stage: resistivity continues to rise; failure stage: resistivity sudden change ≥10%); combine temperature and wind speed data to analyze the failure mechanism such as crystal defect increase, interface debonding or copper matrix cracking caused by interface thermal stress, and form a complete analysis report.

[0037] (13) After the cycle is completed, shut down the instrument and disconnect the main power supply in the following order: heating equipment → air supply device → resistance meter → anemometer → infrared thermometer → computer.

[0038] (14) Take out the sample, observe its appearance and record it (such as whether there are cracks, discoloration, etc.), and cross-verify it with the data results; organize the experimental data, and judge the state of each stage of material thermal fatigue based on the recorded resistivity evolution curve and characteristic parameters, and assist in the analysis of its thermal fatigue failure mechanism.

[0039] Principles and advantages

[0040] The thermal cycling resistivity monitoring device designed in this invention integrates a high thermal conductivity insulation design, a precise temperature change control system, and a high-precision testing system. A detailed analysis and explanation are as follows:

[0041] (1) High thermal conductivity insulating load-bearing system

[0042] Used for mounting experimental samples, solving the balance problem between insulation and heat transfer, and avoiding interference from the metal heating stage with the sample resistance measurement:

[0043] Core materials: High thermal conductivity ceramic insulating boards are used, preferably with processable insulating materials such as AlN and SiC. Specifically, AlN has a thermal conductivity of 170-230 W / m·K at room temperature; 3C-SiC has a thermal conductivity of approximately 500 W / m·K, 4H-SiC approximately 350 W / m·K, and 6H-SiC approximately 320 W / m·K at room temperature, ensuring efficient heat transfer while providing insulation to the heating platform.

[0044] Structural design: Sample support positions and specially structured air ducts are provided on the ceramic insulating plate (sample support stage), such as... Figure 2As shown, the depth of the two grooves is less than the thickness of the ceramic plate. The length is 1.0 to 1.1 times (height of the cylindrical sample + 2 × thickness of the copper patch); the diameter of the sample support position is 1 to 1.1 times the diameter of the cylindrical sample. This design prevents the sample from being blown away significantly during air cooling, ensuring the accuracy and stability of resistance measurement. The air duct grooves increase the area of ​​the sample support stage exposed to the cold air, improving its heat dissipation rate and uniformity. In addition, the air duct groove B connected to the sample support position can also be used to place the resistance meter's wires, ensuring a smooth connection between the wires and both ends of the sample, avoiding resistance measurement errors caused by wire vibration. In particular, an embedded structure is provided below the sample support stage to achieve mechanical assembly with the heating stage below.

[0045] (2) Precision temperature control system

[0046] Based on the data analysis and correlation of thermometers, anemometers, and air supply devices, an adjustable temperature change process is achieved to simulate thermal fatigue performance under different heat dissipation conditions.

[0047] Heating control: The heating rate is set to 10K / min~20K / min; to address the issue of inconsistency between the heating stage temperature and the actual sample temperature caused by the application of a ceramic insulating plate (sample support stage), this problem is alleviated by using a high thermal conductivity insulating material (thermal conductivity ≥170W / m·K) to prepare the insulating plate, ensuring a stable heating rate and reducing heating costs; in particular, it is emphasized that the actual sample temperature is fed back to the heating system in real time through a temperature instrument, rather than referring to the heating stage temperature; in particular, an embedded structure is provided above the heating stage to enable mechanical assembly with the sample support stage above it.

[0048] Cooling control: A customized air supply device (blowing pure gas, without other media) is used. The cold air temperature is determined according to the lowest temperature of the thermal cycling experiment (e.g., if the lowest temperature is 10℃, the cold air temperature is set to 5℃) to create a low-temperature environment around the sample. The cooling rate is controlled at 15K / min~25K / min (before reaching the lowest temperature). The wind speed must be controlled within a reasonable range. If it is lower than this range, the sample cannot be effectively cooled. If it is higher than this range, the sample vibration amplitude will increase, affecting the resistance measurement.

[0049] Temperature control: The holding time is set according to different temperature nodes. The holding time is 5-10 min at the highest temperature (150~200℃), 2-5 min at room temperature (25℃), and 2-5 min at low temperature (10℃). The temperature setting is benchmarked against the operating conditions of high-power devices. The holding time will increase the experimental cost if it exceeds this range, and if it is lower than this range, the sample will not be able to generate effective thermal shock, resulting in a slow rate of crystal defects and microcracks, small resistance fluctuations, and failure to reflect the true thermal fatigue state of the sample.

[0050] Collaborative control logic: The computer-integrated control system connects anemometers, air supply devices, heating equipment, infrared thermometers, and resistance meters to achieve fully automated control of the entire process. The system monitors and records sample temperature changes in real time, calculates and records real-time heating / cooling rates, sets maximum and minimum rate thresholds, and adjusts the working programs of the heating system and air supply devices through data analysis to form negative feedback regulation, ensuring precise and controllable temperature change rate.

[0051] (3) High-precision resistance testing system

[0052] Meets the accuracy, sensitivity, and anti-interference requirements of in-situ monitoring:

[0053] Key parameters: Test range ≥ 1 micro ohm, resolution 0.1 micro ohm, test rate ~50ms / time, ensuring rapid capture of minute changes in resistance.

[0054] Core Material: A preheating process is used to prepare copper material with a stable oxide film to fabricate specially designed circular copper patches. Specifically, for test temperatures of 151~200℃, the recommended oxide film thickness on the surface of the specially designed circular copper patch is 0.9 μm~1.1 μm; for test temperatures of 101~150℃, the recommended oxide film thickness is 0.5 μm~0.7 μm; and for test temperatures less than or equal to 100℃, the recommended oxide film thickness is 140 nm~160 nm. This significantly reduces fluctuations and errors in sample resistance measurement caused by the gradual increase in the oxide film thickness of the copper patch.

[0055] Anti-interference design: It has a thermoelectric potential elimination function to avoid the thermoelectric potential caused by temperature gradient from affecting the measurement accuracy; it adopts the four-wire method to reduce the interference of wire resistance and contact resistance; it replaces the end clamp of the resistance meter wire with a patch type to improve the sample contact stability; it has an intermittent resistance testing function to avoid heating the sample and affecting the measurement accuracy of the sample resistance.

[0056] (4) Auxiliary function components

[0057] Infrared thermometer: A high-precision, high-sensitivity model is selected, which can quickly and in real time provide feedback on the surface temperature of the sample, providing data support for the temperature change control system; in particular, the real-time temperature of the sample is obtained by collecting and analyzing the temperature data of temperature probes A, B and C, and by fitting method.

[0058] Flow channel cover: As a flow channel, it is used to control the airflow direction of the air-cooled equipment to ensure uniform cooling and reduce external environmental interference; in particular, transparent acrylic material is selected to make the flow channel cover for easy observation, and the openings on the flow channel cover are sealed.

[0059] Anemometer: Monitors the airflow speed in the flow channel shroud in real time and synchronizes the data to the computer system to provide a basis for adjusting the cooling rate.

[0060] (5) Material compatibility

[0061] The design for in-situ monitoring of the thermal fatigue properties of diamond-copper composite materials uses equipment and parameters adapted to the thermophysical characteristics of the material, ensuring the accuracy and reliability of the monitoring results.

[0062] This invention, based on the thermal fatigue-resistivity correlation mechanism of diamond-copper composite materials, achieves real-time, accurate, and stable monitoring of the thermal fatigue performance of diamond-copper composite materials by constructing a high thermal conductivity insulating support system, a precise temperature change control system, and a high-precision resistance testing system. First, a computer-integrated system synchronously collects sample resistance, temperature, and wind speed data, dynamically plotting a "resistivity-cycle count" curve to achieve real-time monitoring of each stage of the sample's thermal fatigue process, including crystal defect accumulation, microcrack initiation, and propagation. Second, based on the synergistic effect of a specially designed circular copper patch (with oxide film stabilization), infrared temperature probes A, B, and C used together to fit the sample's real-time temperature, and a high thermal conductivity insulating support stage, the infrared temperature probe D measures the temperature of the sample support stage, effectively eliminating resistance and temperature measurement errors caused by thermoelectric potential, contact resistance, and temperature gradients. Finally, through the limiting structure of the sample support position, airflow guidance via duct channels, wind control via flow channel covers, and real-time wind speed feedback adjustment, the system ensures that the sample does not shift, vibrate, or experience localized overheating during thermal cycling, guaranteeing the repeatability and reliability of the test data. This device provides a novel technical means for early warning and mechanism research of thermal fatigue failure of diamond-copper composite materials for high-power electronic devices. Attached Figure Description

[0063] Figure 1 This is a schematic diagram of the real-time monitoring device for thermal fatigue of diamond-copper composite materials designed in this invention.

[0064] Figure 2 This is a schematic diagram of the sample support stage structure designed for this invention;

[0065] Figure 3 This is a schematic diagram of the heating platform designed for this invention;

[0066] Figure 4 This is a characterization diagram of the interface of the diamond-copper composite material after 600 cycles of cyclic testing in Example 1 of the present invention after thermal fatigue.

[0067] Figure 5 This is a schematic diagram of the flow channel cover structure designed for this invention;

[0068] Figure 6 This is a schematic diagram of the special circular copper patch and diamond-copper composite material sample designed in this invention.

[0069] from Figure 1 As can be seen from the diagram, the monitoring device consists of a computer system, a heating stage, a resistance meter, an air supply device, a sample support stage, a flow channel hood, an anemometer, and four thermometers. Thermometers A, B, and C are used to monitor the temperature of the diamond-copper composite material, while thermometer D is used to monitor the temperature of the sample support stage.

[0070] from Figure 2 As can be seen, the sample support platform has a sample support position and an air duct groove, and it has an embedded structure below it, which can realize mechanical assembly with the heating platform below.

[0071] from Figure 3 As can be seen, the heating stage has an embedded structure on top, which allows it to be mechanically assembled with the sample support stage above it.

[0072] from Figure 4 It can be seen that after 600 thermal cycles, the diamond-copper composite material developed obvious microcracks at the interface between diamond and copper, which is the main reason for the significant increase in the sample's resistance.

[0073] from Figure 5 As can be seen, the flow channel cover has openings at both ends, with dimensions of 300mm × 150mm × 80mm.

[0074] from Figure 6 As can be seen, there is a circular copper patch on each of the left and right end faces of the diamond-copper composite material sample. Detailed Implementation

[0075] To make the objectives, technical solutions, and advantages of the present invention clearer, the following detailed description is provided in conjunction with specific embodiments and comparative examples.

[0076] All equipment in the embodiment includes a resistance meter, a heating stage, a sample support stage, a flow channel hood, an air supply device, an anemometer, a specially made circular copper patch, a first set of temperature measuring devices, a second set of temperature measuring devices, and a data collection and analysis device.

[0077] The resistance meter is connected to the end face of the cylindrical sample to be tested via a wire with a specially designed circular copper patch (12.7 mm in diameter and with an oxide layer thickness of approximately 0.6 micrometers). The cylindrical sample to be tested is placed horizontally on the sample support stage. The sample support stage has an air duct and a sample support position, which is a recessed semi-cylindrical hole. The sample support position and the cylindrical sample to be tested form a clearance fit. The first set of temperature measuring devices includes three temperature measuring probes. The first temperature measuring probe is located on the top of the flow channel cover and perpendicular to the sample support position, with the measuring point aligned with the geometric center of the sample. This probe is defined as probe A. The second temperature measuring probe is located to the left of probe A, with the measuring point aligned with the axial center of the left end face of the sample. This probe is defined as probe B. The third temperature measuring probe is located to the right of probe A, with the measuring point aligned with the axial center of the right end face of the sample. This probe is defined as probe C. The second set of temperature measuring devices is located on the flow channel cover and faces the sample support stage. It is used to collect the temperature data of the sample support stage. This probe is defined as probe D.

[0078] The thermal conductivity of the sample support stage is greater than 150 W / m·K; the sample support stage is set on the heating stage, the anemometer is set on the top of the flow channel cover, and the air supply device is set on the side of the flow channel cover close to the anemometer.

[0079] The anemometer, the first set of temperature measuring devices, and the second set of temperature measuring devices are connected to the data collection and analysis device via wires.

[0080] The specially made circular copper patch is a circular copper patch that has undergone preheating treatment at a temperature of 170°C. The preheating environment contains oxygen, and the volume percentage of oxygen is approximately 20%.

[0081] The sample support stage is equipped with an air duct. This air duct allows for rapid heat dissipation between the heating stage and the sample support stage during sample cooling, thereby promoting sample cooling.

[0082] The thickness of the circular copper patch is approximately 2.5 mm, and the copper patch is assembled with the sample by extrusion.

[0083] Acrylic sheets are used to fabricate the flow channel cover for visualization. An opening is made at the top of the flow channel cover for mounting an anemometer and a temperature probe, and the opening is sealed.

[0084] The upper surface of the sample support stage (i.e., the surface where the sample support position is located) is provided with an air duct groove A; the two end faces of the sample support position are directly opposite the air duct groove B, which is located on the upper surface of the sample support stage. The thickness of the sample support stage is 18mm.

[0085] The depth of air duct A is 3mm; its length is equal to the length of the sample support stage; the width of air duct A is 6mm, and there are 2 air ducts A.

[0086] The depth of air duct B is 3mm; the width of air duct B is 6mm. Its length plus the reserved space for the sample support equals the length of the sample support stage.

[0087] The sample support area is a recessed semi-cylindrical shape, with a length of 1.05 times (height of cylindrical sample + 2 × thickness of copper patch); the diameter of the sample support area is 1 time the diameter of the cylindrical sample.

[0088] Example 1

[0089] (1) Experimental sample: Diamond-copper composite material sample (size φ12.7×15mm), which was pretreated by "polishing the oxide layer with 400 grit sandpaper → ultrasonic cleaning with alcohol for 10min → hot air drying at 50℃ for 5min → gold spraying".

[0090] (2) Core device and parameters: The support device is an AlN ceramic plate (150mm×18mm×50mm), with a sample support position with a depth of 7.4mm (matching the sample, gap ≤1mm) and two equidistant air duct slots A with a width of 6mm on the upper surface.

[0091] The depth of the air duct A is 3mm; its length is equal to the length of the sample support stage; there is one air duct B on each of the two end faces of the sample support position. The depth of the air duct B is 3mm, and its length plus the allowance of the sample support position equals the length of the sample support stage. The width of both air ducts A and B is 6mm.

[0092] (3) Temperature change parameters: heating rate 18K / min, maximum temperature 150℃ for 8min; cooling rate 20K / min, cold air temperature 5℃, wind speed 5m / s, low temperature 10℃ for 3min, room temperature 25℃ for 3min.

[0093] (4) Testing system: Four-wire resistance meter (test range 1 micro ohm to 100 milliohms, resolution 0.1 micro ohm, speed 50 ms / time, with thermoelectric potential elimination function), the ends of the wires are connected with special circular copper patches (the surface of the special circular copper patches has an oxide layer of 0.6 micrometers); four infrared thermometers are used in series (accuracy ±0.1℃).

[0094] (5) Experimental process: Strictly follow the procedure of “experimental preparation → preheating verification → thermal cycle execution → data acquisition”, and cycle a total of 600 times, and collect resistance, temperature and wind speed data in real time.

[0095] (6) Experimental results: The resistivity exhibits a three-stage characteristic. The resistance fluctuation is ≤0.5% from 0 to 167 times. During the process from 168 to 433 times, the crystal defect density of the sample gradually increases, resulting in a slow increase in resistance. During the process from 434 to 600 times, microcracks are generated at the diamond-copper interface in the sample, resulting in a gradual acceleration of the increase in resistance.

[0096] (7) Test stability: The sample has no offset or vibration, the resistance data fluctuates within ±0.7μΩ, and the temperature control error is ≤±0.6K, which meets the requirements for thermal fatigue performance evaluation.

[0097] (8) Measurements showed that before thermal fatigue cycling, the sample resistance was 5.862 mΩ and the thermal conductivity was 730 W / m·K; after 167 cycles, the resistance was 5.923 mΩ (an increase of 1.04% from the initial value, consistent with the characteristics of the initial stable stage); after 433 cycles, the resistance was 6.445 mΩ (an increase of 9.95% from the initial value, corresponding to the stage of increased crystal defects); after the end of the cycle, the resistance was 7.547 mΩ (an increase of 28.74% from the initial value, corresponding to the stage of microcrack initiation), and the thermal conductivity was 605 W / m·K, a decrease of 125 W / m·K from the initial value, a decrease of 17.12%.

[0098] Comparative Example 1 (Comparison of Insulation Materials)

[0099] The only difference from Example 1 is that the sample support stage is replaced with an Al2O3 ceramic plate (thermal conductivity 29 W / m·K), while all other parameters are the same.

[0100] Tests revealed that due to the poor thermal conductivity of the Al2O3 ceramic plate, the complete single thermal cycle was 8.5 minutes longer than in Example 1; after 500 cycles, the sample resistance change rate was <6%, failing to accurately reflect the performance degradation during the microcrack initiation stage, thus rendering the data of low reference value. This is because the thermal conductivity of Al2O3 ceramic is only 14.5% of that of AlN ceramic, resulting in low heat exchange efficiency between the sample and the sample support platform, and a delayed temperature response.

[0101] Comparative Example 2 (Comparison of specially made circular copper patches)

[0102] The only difference from Example 1 is that the specially made circular copper patch is replaced with an ordinary copper patch, while the other parameters are the same.

[0103] Tests revealed that the sample resistance data fluctuated with increasing thermal cycling cycles, ranging from ±2.9 μΩ, resulting in low data reference value. This is because the thickness of the oxide film on ordinary copper surfaces increases with the number of thermal cycles, leading to micro-vibrations in the sample and dynamic shifts in the resistance data, thus increasing the measurement error.

[0104] Comparative Example 3 (Comparison of four thermometers used in combination)

[0105] The only difference from Example 1 is that the four infrared thermometers used in combination are replaced with three infrared thermometers used in combination, and the temperature probe used for measuring the axial center temperature on the right side of the sample is missing, i.e., probe C is missing. All other parameters are the same.

[0106] Tests revealed a significant discrepancy between the measured and actual sample temperatures, with fluctuations of ±2.3℃, rendering the data of low reference value. This is attributed to a small temperature gradient within the sample, particularly from left to right, which amplifies the measurement error.

[0107] Comparative Example 4 (Structural Design Comparison: Grooveless Design)

[0108] The AlN ceramic plate did not have a sample support position or air duct groove. The sample was placed directly on the surface of the plate. The other parameters were the same as in Example 1.

[0109] The sample exhibited poor stability, shifting by 0.5–1.2 mm during air cooling, with resistance fluctuations of ±4.0 μΩ, eight times that of Example 1. The ceramic plate lacked airflow guidance channels on its surface, resulting in uneven heat dissipation and a cooling rate fluctuation of ±3 K / min, exceeding the standard range of ±1 K / min. The primary reasons for this were the absence of proper positioning of the sample support and the lack of airflow guidance from the airflow channels, leading to a dual decrease in mechanical stability and heat flow uniformity.

[0110] Comparative Example 5 (Comparison of load-bearing device structures: only air duct slot A is open)

[0111] The AlN ceramic plate only has a sample support position and an air duct groove A. No air duct grooves B (circuit grooves) are opened on both sides of the sample support position end face. The wires are placed directly on the plate surface. The other parameters are the same as in Example 1.

[0112] Because the wires lack space for fixing and clearance, their elasticity leads to poor contact between the wire patch and the sample, resulting in a random error in resistivity calculation that is about 30% higher than in Example 1. At the same time, the absence of a wire groove affects the uniform heat dissipation capacity of the sample, resulting in a local temperature difference of 2°C on the sample surface, which exceeds the uniformity requirement of ±0.5°C and affects the accuracy of the temperature-resistivity relationship.

[0113] Comparative Example 6 (Cooling Rate Comparison: Low-Speed ​​Cooling)

[0114] The cooling rate was reduced to 10 K / min (the wind speed was reduced to 2 m / s), and the other parameters were the same as in Example 1.

[0115] The testing efficiency was low, with the cooling stage alone taking about 60% longer than Example 1. At the same time, the thermal shock strength of the sample was insufficient, resulting in only about 40% of the number of microcracks after 600 cycles compared to Example 1, and the final resistivity changed by only about 5% of the initial value. This made it difficult to effectively excite and evaluate the ultimate performance degradation of the material under severe thermal shock.

[0116] Comparative Example 7 (Cooling Rate Comparison: High-Speed ​​Cooling)

[0117] The cooling rate was increased to 30 K / min (the air speed was increased to 18 m / s), and the other parameters were the same as in Example 1.

[0118] During the test, there was severe mechanical interference, the sample vibrated significantly, and the resistance data fluctuated by ±1.9μΩ. About 30% of the collected data could not be used for accurate analysis due to the superposition of high-frequency vibration noise. In particular, excessive thermal shock and vibration caused the sample to crack locally before 600 cycles.

[0119] Comparative Example 8 (without flow channel protection)

[0120] The only difference from Example 1 is that a transparent flow channel cover was not installed above the sample and the carrier device; all other parameters are the same.

[0121] Tests revealed that the fluctuations in heating and cooling rates increased significantly during thermal cycling. After 150 cycles, the resistance data exhibited irregular fluctuations, making it impossible to distinguish the three stages of resistivity change. This was attributed to the lack of a flow channel shroud, which resulted in turbulent cooling airflow, uneven temperature field distribution, and deviations in the actual heating / cooling conditions of the sample surface from the set operating conditions, thus causing data drift and distortion of stage characteristics.

Claims

1. A real-time monitoring device for the thermal fatigue properties of diamond-copper composite materials, characterized in that: It includes a resistance meter, heating stage, sample support stage, flow channel cover, air supply device, anemometer, specially made circular copper patch, first set of temperature measuring device, second set of temperature measuring device, and data collection and analysis device; The resistance meter is connected to the end face of the cylindrical sample to be tested via a wire with a specially designed circular copper patch at the end. The cylindrical sample to be tested is placed horizontally on the sample support stage. The sample support stage has an air duct and a sample support position. The sample support position is a recessed semi-cylindrical hole, and the sample support position and the cylindrical sample to be tested form a clearance fit. The first set of temperature measuring devices includes three temperature measuring probes. The first temperature measuring probe is set on the top of the flow channel cover and perpendicular to the sample support position, with the measuring point aligned with the geometric center of the sample. This probe is defined as probe A. The second temperature measuring probe is located to the left of probe A, with the measuring point aligned with the axial center of the left end face of the sample. This probe is defined as probe B. The third temperature measuring probe is located to the right of probe A, with the measuring point aligned with the axial center of the right end face of the sample. This probe is defined as probe C. The second set of temperature measuring devices is set on the flow channel cover and faces the sample support stage to collect the temperature data of the sample support stage. This probe is defined as probe D. The thermal conductivity of the sample support stage is greater than 150 W / m·K; the upper surface of the sample support stage is provided with air duct grooves; The specially made circular copper patch is connected to the end face of the sample to be tested. The specially made circular copper patch is a circular copper patch that has undergone preheating treatment. The preheating treatment is to perform surface treatment on the pure copper sample in a high-precision resistance furnace at a certain temperature and holding time. The preheating treatment temperature must be higher than the highest test temperature.

2. The real-time monitoring device for the thermal fatigue properties of diamond-copper composite materials according to claim 1, characterized in that: The sample support platform is set on the heating platform, the anemometer is set on the top of the flow channel cover, and the air supply device is set on the side of the flow channel cover and close to the anemometer. The anemometer, the first set of temperature measuring devices, and the second set of temperature measuring devices are connected to the data collection and analysis device via wires.

3. The real-time monitoring device for the thermal fatigue properties of diamond-copper composite materials according to claim 1, characterized in that: The preheating treatment involves surface treatment of pure copper samples using a high-precision resistance furnace at a certain temperature and holding time. The preheating temperature is 130~230℃, and the preheating environment contains oxygen with a volume percentage of less than or equal to 21%.

4. The real-time monitoring device for the thermal fatigue properties of diamond-copper composite materials according to claim 3, characterized in that: For tests with a maximum temperature of 151~200℃, the recommended thickness of the oxide film on the surface of the specially made circular copper patch is 0.9 μm~1.1 μm; for tests with a maximum temperature of 101~150℃, the recommended thickness of the oxide film on the surface of the specially made circular copper patch is 0.5 μm~0.7 μm. For applications where the maximum test temperature is less than or equal to 100°C, the recommended thickness of the oxide film on the surface of the specially designed circular copper patch is 140 nm to 160 nm.

5. The real-time monitoring device for the thermal fatigue properties of diamond-copper composite materials according to claim 1, characterized in that: The thickness of the circular copper patch is 2-2.5 mm, and the contact area between a single specially made circular copper patch and one end of the sample to be tested is greater than 100 mm². 2 Preferably 100~150 mm 2 The copper patch is in close contact with the sample.

6. The real-time monitoring device for the thermal fatigue properties of diamond-copper composite materials according to claim 1, characterized in that: Acrylic sheets are used to fabricate the flow channel cover for visualization. An opening is made at the top of the flow channel cover for mounting an anemometer and a temperature probe, and the opening is sealed.

7. The real-time monitoring device for the thermal fatigue properties of diamond-copper composite materials according to claim 1, characterized in that: The sample support stage is made of processable insulating materials such as AlN and SiC.

8. The real-time monitoring device for the thermal fatigue properties of diamond-copper composite materials according to claim 1, characterized in that: The upper surface of the sample support stage, i.e. the surface where the sample support position is located, is provided with an air duct groove A; the two end faces of the sample support position are directly opposite the air duct groove B, and the air duct groove B is located on the upper surface of the sample support stage. The depth of the air duct A is 2-4 mm, preferably 3 mm; its length is equal to the length of the sample support stage; the width of the air duct A is 5-8 mm, preferably 6 mm; and the number of air ducts A is greater than or equal to 2. The depth of the air duct B is 2-4 mm, preferably 3 mm; the width of the air duct B is 5-8 mm, preferably 6 mm; and its length is equal to the length of the sample support stage. The sample support area is a recessed semi-cylindrical shape with a length of 1.0 to 1.1 times (height of cylindrical sample + 2 × thickness of copper patch); the diameter of the sample support area is 1 to 1.1 times the diameter of the cylindrical sample.

9. A method of using the real-time monitoring device for the thermal fatigue properties of diamond-copper composite materials as described in any one of claims 1-8, characterized in that: Includes the following steps: (1) Sample pretreatment: The diamond-copper composite cylindrical sample was subjected to surface oxide layer grinding, alcohol ultrasonic cleaning, hot air drying and gold spraying in sequence to ensure that the sample surface was free of oil, impurities and oxide film. (2) Experimental preparation and system assembly: The pretreated cylindrical sample is placed horizontally into the sample support position of the sample support platform. The resistance meter wire is fixed through the line groove, i.e., the air channel groove B, to ensure a stable connection between the sample and the specially made circular copper patch at the end of the resistance meter wire. The sample support platform with the sample is embedded in the middle of the heating platform of the customized heating equipment, with a positioning deviation of ≤1mm. An external flow channel cover with openings at both ends is installed as a flow cavity. The anemometer is placed 5cm away from the sample inside the flow channel cover. The air supply device with an air volume ≥50m³ / h is installed at the air inlet on the right side of the flow cavity. The probe of infrared thermometer A is set on the top of the flow channel cover and perpendicular to the sample support position. The temperature measurement point is aligned with the geometric center of the sample, and the temperature measurement distance is set to 10cm. The temperature measurement point of the probe of infrared thermometer B is aligned with the axial center of the left end face of the sample and 3cm away from probe A. The temperature measurement distance is set to 10-11cm. The temperature measurement point of the probe of infrared thermometer C is aligned with the axial center of the right end face of the sample and 3cm away from probe A. The temperature measurement distance is set to 10-11cm; the probe of the infrared thermometer D is directly facing the sample support stage, 3cm away from probe A, and is used to measure the temperature of the sample support stage. (3) Instrument startup: Start the equipment in the order of "infrared thermometer → anemometer → resistance meter → computer integrated system", set the resistance meter sampling frequency to 20Hz, the infrared thermometer temperature measurement accuracy to ±0.5℃, and the computer system to start the data synchronous acquisition mode; (4) Preheating and Cyclic Verification: Heat the sample support stage to 80℃ at a rate of 10K / min~20K / min and hold for 10min to ensure uniform overall sample temperature with a temperature difference ≤2℃; then turn off the heating equipment and cool it down to room temperature by air cooling; monitor the sample temperature change in real time, monitor the sample surface with an infrared thermometer, and ensure the temperature difference is ≤3℃ and the heating / cooling rate fluctuation is within ±1K / min; check whether the resistance meter data is stable; if there is uneven temperature or abnormal data, the sample installation position needs to be readjusted or the wires need to be replaced. (5) Heating stage: The computer system issues an instruction, and the heating equipment heats the sample to 150~200℃±1℃ at a rate of 10K / min~20K / min and holds it for 5~10min; during the heating process, the temperature data is fed back in real time. If the temperature exceeds ≥3℃, the system will automatically trigger the heating pause protection. (6) Cooling stage: The heating equipment is automatically shut down and the air supply device is immediately started. The air speed is adjusted to 10~15m / s by computer and the cooling rate is controlled to be 15K / min~25K / min. After cooling down to 10℃±1℃, the temperature is maintained for 2~5min. During the cooling process, the anemometer monitors the airflow stability in real time, and the fluctuation range is ≤±0.5m / s. (7) Room temperature transition stage: Reduce the air supply speed to 5m / s to allow the sample temperature to slowly rise back to room temperature and keep it warm for 2~5min; before the end of the transition stage, record the initial stable value of the sample resistance as a reference for subsequent comparison. (8) Real-time data acquisition: The resistivity meter records the instantaneous resistance value of the sample and automatically saves it to the designated folder; the computer system automatically calculates the resistivity according to the formula "resistivity = resistance × cross-sectional area / length"; the sample temperature data collected by the infrared thermometer and the real-time wind speed data of the anemometer are recorded simultaneously, and the time of the three is precisely aligned to ensure that the error is ≤0.1s; (9) Data anomaly handling: If a set of data jumps, immediately pause the cycle, check whether the sample has cracked, debonded or other phenomena, and after troubleshooting, re-execute the cycle and mark "retest" in the data record; (10) Cyclic execution: Repeat the "thermal cycle core execution" and "data acquisition" steps, with the number of cycles set to 400~700 times; pause for 5 minutes after every 100 cycles, check the appearance of the sample and the connection status of the equipment to ensure the continuity of the test; (11) Results analysis: Plot the "resistivity-cycle number" evolution curve and extract characteristic parameters.

10. The method of using the real-time monitoring device for the thermal fatigue properties of diamond-copper composite materials according to claim 9, characterized in that: The thermal fatigue stages are divided according to the curve trend: Initial steady-state phase: resistivity fluctuation ≤2%; Fatigue development stage: resistivity continues to rise; Failure stage: resistivity change ≥10%; By combining temperature and wind speed data, the failure mechanisms such as crystal defect increase, interface debonding, or copper matrix cracking caused by interfacial thermal stress are analyzed, and a complete analysis report is generated.

Images