Contact and non-contact combined sensing method and online monitoring system suitable for temperature online monitoring of power semiconductor chip

Abstract

The application discloses a contact and non-contact combined sensing method and an online monitoring system suitable for power semiconductor chip temperature online monitoring, and comprises the following steps: thermocouple insulation packaging, chip temperature measuring point determination, chip surface thermocouple integration, infrared radiation window preparation, infrared module integration, thermocouple temperature calibration, infrared module temperature measurement calibration, insulation voltage resistance inspection and online monitoring function verification. Through the insulation packaging and integrated installation of the thermocouple, the pre-preparation of the power semiconductor chip infrared radiation window and the integrated installation of the infrared temperature measurement module, the real-time online contact and non-contact combined measurement of the power semiconductor device chip temperature is realized, the shortcomings of the traditional electrical parameter method depending on a model and the thermistor method being slow in response and position limited are overcome, the original main structure and electrical performance of the module are not changed, the integrated cost is low, signal acquisition is convenient, and the scheme is high in maturity.

Description

Technical Field

[0001] This invention relates to the fields of packaging, testing and thermal management technology of power semiconductor modules, and in particular to a contact and non-contact combined sensing method and online monitoring system suitable for online temperature monitoring of power semiconductor chips. Background Technology

[0002] With the rapid development of electrification applications such as new energy power generation, electric vehicles, and rail transportation, power semiconductor modules are evolving towards higher power density and higher reliability. Accurate and real-time monitoring of chip temperature is crucial for optimizing system performance, predicting lifespan, and ensuring reliability. However, traditional temperature monitoring methods are insufficient to meet the increasingly demanding measurement requirements.

[0003] Currently, temperature measurement methods for power semiconductor modules mainly include the electrical parameter method and the built-in thermistor method. The electrical parameter method is an indirect temperature measurement method, which relies on precise sampling circuits and complex offline calibration models. Its online measurement accuracy is easily affected by circuit parasitic parameters, drive fluctuations, and sampling errors. Although the built-in thermistor method can directly output temperature signals, the thermistor is usually placed on the substrate, and there is a large thermal resistance and thermal capacitance between it and the chip. This results in slow response, a significant temperature difference between the measurement result and the actual junction temperature of the chip, and it cannot reflect the temperature distribution inside the chip or between different chips.

[0004] Infrared radiation thermometry, as a non-contact temperature measurement method, has advantages such as high accuracy and insulation. However, a bottleneck problem in applying infrared thermometry to power semiconductor devices is that the surface of power semiconductor device chips is usually covered with organic potting materials such as silicone gel or epoxy resin. The CH and HO bonds in these materials have a strong absorption effect on mid- and far-infrared light, while the chip's radiation within its normal operating temperature range is mainly in the mid- and far-infrared band. The potting compound blocks the penetration of the chip's infrared radiation signal, failing to meet the requirements of infrared thermometry. If the encapsulation shell or potting material is removed to implement infrared thermometry, the module's insulation protection and environmental barrier functions will be compromised, leading to a decrease in device reliability. Therefore, traditional infrared thermometry methods lack engineering practicality.

[0005] Therefore, how to achieve rapid, accurate, and reliable online measurement of chip junction temperature without affecting the electrical performance and packaging reliability of the power module has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the aforementioned problems in existing technologies, this invention proposes a combined contact and non-contact sensing method and online monitoring system suitable for online temperature monitoring of power semiconductor chips, achieving high-precision, fast-response, and highly reliable online monitoring of chip temperature.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A combined contact and non-contact sensing method for online temperature monitoring of power semiconductor chips includes the following steps: 1) Thermocouple insulation encapsulation. Select K-type thermocouple wire with a diameter of 0.5mm~0.25mm and a capillary tube with an outer diameter of less than 1mm and an inner diameter slightly larger than the thermocouple wire diameter; insert the K-type thermocouple wire into one end of the capillary tube, with the temperature sensing contact extending to the other end of the capillary tube, and the distance from the temperature sensing contact to the other end of the capillary tube is 1~2mm; use high thermal conductivity insulating adhesive (such as Kraft 52 series insulating adhesive) to seal both ends of the capillary tube by dispensing, keep it warm and let it cure for use, forming a thermocouple.

[0008] The capillary material is a high thermal conductivity and high insulation material, such as quartz or high-purity alumina ceramic.

[0009] 2) Determination of chip temperature measurement points. Select the power semiconductor specification and model, establish an electrothermal coupling finite element model, conduct finite element simulations under different heat flux density conditions, evaluate the temperature distribution inside the power semiconductor, and mark the highest temperature position of the chip as the temperature measurement point; according to the internal topology type of the power semiconductor device, mark the highest temperature position of the chip at each level, and record the temperature measurement point requirements for all level chips.

[0010] The electrothermal coupling finite element model includes the chip, metal bonding wires, DBC substrate, potting compound, and heat sink, and the simulation covers 50% to 120% of the device's rated operating heat flux density. 3) Chip-surface thermocouple integration. Select an unencapsulated power semiconductor and pre-fabricate through-holes on the side or top of the plastic casing. The number of through-holes is determined based on the number of temperature sensing points marked in step 2). The diameter of the through-holes is slightly larger than the outer diameter of the capillary. The thermocouples encapsulated in step 1) are bonded to the temperature sensing points marked in step 2) using high-temperature thermally conductive insulating adhesive by dispensing, and then allowed to cure under heat. The other end of the thermocouple lead is led out through the through-hole of the plastic casing and fixed and sealed (the through-hole seal uses epoxy resin) to form an integrated thermocouple power semiconductor. The lead is connected to the temperature acquisition module.

[0011] 4) Infrared Radiation Window Fabrication. The integrated thermocouple power semiconductor chip contains metal bonding wires, which form an arch shape on the chip surface (arch height 3-4 mm). The power semiconductor is placed flat, and a mold is placed on the top of the metal bonding wire arch and in the central area of ​​the chip, with its bottom surface parallel to the chip surface, covering the central area of ​​the chip. The height of the mold is greater than the potting liquid level, and its density is greater than the density of the potting adhesive, so that the weight of the mold is greater than the buoyancy of the potting adhesive, and good contact is maintained with the top of the metal bonding wire arch during potting. Subsequently, the potting adhesive is injected into the power semiconductor, and it is moved into a vacuum chamber for vacuum degassing and heating for curing. After the potting adhesive is completely cured, the mold is removed, forming an infrared radiation window (e.g., with a thickness of 3 mm-4 mm) that is flush with the height of the metal bonding wire arch. Because the infrared radiation window area retains a thin layer of high emissivity potting adhesive (surface emissivity ≥ 0.90), and the heat conduction is enhanced by the metal bonding wires and thermally conductive particles, the chip temperature can be transferred to the surface of the infrared radiation window within tens of milliseconds.

[0012] In this process, insulating high thermal conductivity particles are added to the potting compound (such as polydimethylsiloxane AB component), stirred evenly, and vacuum degassing is performed. The insulating high thermal conductivity particles are selected from one or more combinations of oxide ceramics, carbide ceramics, nitride ceramics, or diamond, with a particle size of W3~W5 micrometers. The amount of insulating high thermal conductivity particles added accounts for 5%~20% of the mass of the potting compound. Insulating high thermal conductivity particles are used to enhance the thermal conductivity of potting compounds. The particle size is selected in the micron range, which increases the thermal conductivity enhancement effect of the particles while avoiding particle agglomeration and sedimentation.

[0013] 5) Infrared Module Integration. A miniature infrared module is selected, employing an uncooled infrared sensor chip (such as GD60914A), which has data sampling and transmission functions, a temperature measurement range covering the operating temperature range of the semiconductor device chip, and a temperature measurement frequency of not less than 25Hz. The miniature infrared module is mounted on a plastic shell integrating a thermocouple power semiconductor, and the infrared probe of the miniature infrared module is vertically aligned with the infrared radiation window. The distance between the infrared probe and the infrared radiation window satisfies L≤0.5D, where L is the distance between the infrared probe and the infrared radiation window, and D is the lateral dimension of the infrared radiation window.

[0014] 6) Thermocouple temperature calibration. Place the integrated thermocouple power semiconductor in a constant temperature chamber and perform multi-point calibration of the thermocouple within the range of room temperature to 150℃; the calibration temperature points should be no less than 7 (e.g., 30℃, 50℃, 70℃, 90℃, 110℃, 130℃, 150℃), and the holding time at each calibration temperature point should be ≥20 minutes to ensure that the internal temperature of the power semiconductor is constant. Then, use a numerical multimeter or temperature recorder to collect the thermocouple measurement temperature and establish a mapping relationship between the thermocouple measurement temperature and the constant temperature chamber setting temperature. After calibration, the thermocouple measurement error should be within 1℃.

[0015] 7) Infrared module temperature measurement calibration. A low-voltage DC loading platform was used to conduct constant current loading experiments on the integrated thermocouple power semiconductor device until thermal steady state. The chip temperature measured by the thermocouple and the infrared radiation window temperature measured by the miniature infrared module were collected simultaneously to establish a calibration model between the chip temperature and the infrared radiation window temperature. The calibration model is a linear relationship ΔT = a·T_chip + b, where ΔT is the difference between the chip temperature and the infrared radiation window temperature, T_chip is the chip temperature, and a and b are calibration coefficients. After calibration, the measurement error of the infrared module is within 3℃.

[0016] 8) Insulation withstand voltage test. Short-circuit all terminals (including power terminals and auxiliary terminals) of the integrated thermocouple power semiconductor with metal wires; short-circuit the thermocouple connection terminals and the power semiconductor substrate with metal wires; use an insulation withstand voltage tester to perform insulation withstand voltage tests on the power semiconductor terminals and substrate, referring to the national or military standards for insulation withstand voltage testing of power semiconductor devices, to verify the insulation withstand voltage performance of the surface-integrated thermocouple of the power semiconductor.

[0017] 9) Online monitoring function verification. The power semiconductor is transferred to a switching pulse test platform. Under typical operating conditions, the controller operates continuously on and off. Based on the integrated thermocouple and miniature infrared module, online chip temperature monitoring and electromagnetic interference immunity tests are conducted. Temperature curves of the thermocouple and miniature infrared module are collected, and the infrared measurement temperature is calibrated according to the calibration model of chip temperature and infrared radiation window temperature. The abnormal spikes on the temperature change curve are observed to verify the online temperature monitoring function and anti-interference capability of the integrated sensor chip.

[0018] A power semiconductor chip temperature online monitoring system is also provided, prepared using the method described above, comprising: Contact temperature measurement unit: Composed of an insulated thermocouple array, used to directly measure the surface temperature of the chip; Non-contact temperature measurement unit: Composed of a miniature infrared module integrated into a plastic housing, used to measure the temperature of the infrared radiation window; Data processing unit: Built-in calibration model of chip temperature and infrared radiation window temperature, which corrects the output signal of the miniature infrared module in real time and verifies it with thermocouple measurement data; Insulation protection unit: Composed of potting compound and insulating encapsulation structure, it ensures the electrical safety of the system under high voltage environment.

[0019] The present invention features a contact thermocouple that is directly attached to the chip hot spot, with a measurement error within ±1℃; the non-contact infrared module achieves millisecond-level temperature response through a low-thickness, high-thermal-conductivity window, and combined with a calibration model, the error can be controlled within ±3℃, thus solving the problem of lag response of traditional thermistors.

[0020] Secondly, the thermocouple of this invention employs a double encapsulation of quartz / ceramic capillary tubes and high thermal conductivity insulating adhesive, verified by insulation withstand voltage testing (e.g., AC 4000V / 1min leakage current <2mA), meeting the safety requirements of high-voltage devices. The infrared window retains a thin layer of potting compound, without damaging the original insulation and protection structure of the module, and is compatible with existing encapsulation processes. It boasts strong anti-interference capabilities: the thermocouple leads are shielded and sealed within the housing, the infrared module is integrated into the housing, and the signal undergoes digital filtering, resulting in distortion-free temperature measurement waveforms under 1kHz high-frequency switching conditions, adapting to the strong electromagnetic environment of power devices.

[0021] Third, this invention accurately locates hot spots through electrothermal coupling simulation, and combines the thermal conductivity enhancement of potting compound with window prefabrication process to realize the application of infrared thermometry in engineered power modules; all calibration and verification processes are standardized, which facilitates large-scale promotion.

[0022] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention achieves real-time online contact and non-contact combined measurement of the temperature of power semiconductor device chips by insulating encapsulation and integrated installation of thermocouples, prefabrication of infrared radiation windows of power semiconductor chips, and integrated installation of infrared temperature measurement modules. This overcomes the shortcomings of traditional electrical parameter methods, which rely on models, and the slow response and location limitations of the thermistor method. It does not change the original main structure and electrical performance of the module, has low integration cost, convenient signal acquisition, and high solution maturity. Furthermore, after experimental verification under harsh operating conditions such as power cycling and high-frequency switching, it shows excellent reliability and anti-interference ability, providing a high-precision temperature data foundation for the thermal management, condition monitoring, and reliability assessment of power modules. Attached Figure Description

[0023] Figure 1 A diagram showing the temperature field distribution of power semiconductors and the marking of temperature measurement points; Figure 2 Temperature calibration diagram for integrated thermocouple thermostat; Figure 3 Temperature calibration curves for power semiconductor integrated miniature infrared modules; Figure 4 Test diagram of continuous switching pulse for power semiconductors with integrated temperature sensing Figure 5 This diagram demonstrates the verification of the online temperature monitoring function for power semiconductor chips. Detailed Implementation

[0024] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a comprehensive overview of the contact and non-contact combined sensing method for online temperature monitoring of power semiconductor device chips according to the present invention.

[0025] I. Thermocouple Insulation Encapsulation Thermocouple insulation encapsulation is the foundation of this invention. In this embodiment, an ultra-fine thermocouple wire with a diameter of 0.25 mm is used. When power semiconductors are operating, an alternating high-voltage electric field exists on the chip surface. Thermocouples need to be in close contact with the chip during temperature measurement. If the thermocouple is not insulated, the high electric field on the chip surface may break down the thermocouple's acquisition circuit, forming a discharge loop to ground, leading to catastrophic consequences. Therefore, to provide insulation protection for the thermocouple, insulating varnish is first evenly sprayed onto the thermocouple's temperature-sensing contacts and leads, and then dried. A fine-diameter, high-purity quartz capillary tube (outer diameter 0.5 mm, inner diameter 0.32 mm) is then used to insert the thermocouple's temperature-sensing contacts from one end of the quartz tube, extending to the other end, approximately 1 mm from the port. High-temperature resistant, insulating, and highly thermally conductive adhesive (Kraft 52 series) is used to seal both ends of the quartz tube, fixing the thermocouple's position within the tube and preventing accidental removal during installation and connection. This completes the insulated thermocouple sample and its internal structure.

[0026] II. Determination of Chip Temperature Measurement Points The highest temperature point in the chip's central region is the highest junction temperature of the chip, which is monitored online using integrated thermocouples. Therefore, this invention preferably uses the chip's geometric center as the temperature measurement point. Based on a thermal finite element simulation platform, the temperature distribution of the power semiconductor device chip is extracted under typical operating conditions. The highest temperature region is selected and marked as the temperature measurement point according to the chip distribution. For multi-level topologies and multi-chip parallel power semiconductors, at least the highest temperature position of each level of parallel chip is selected for installation. If there is a need to measure the temperature distribution differences between parallel chips, thermocouples can also be installed on several or all chips. Figure 1 As shown.

[0027] III. Chip Surface Thermocouple Integration Select an unencapsulated power semiconductor device sample and install one end of the encapsulated thermocouple's temperature-sensing contact onto the marked temperature-sensing point. During installation, use a small amount of insulating, high-thermal-conductivity adhesive to assist in fixation and heat conduction, ensuring full contact between the sensing end and the chip surface. Simultaneously, avoid applying undue mechanical stress to the thermocouple wires. Pre-fabricate micro-lead vias at appropriate locations on the plastic housing, leading the thermocouple leads out through these vias using the shortest and most direct path to minimize impact on the module's internal space. After the leads are led out, use sealing materials such as epoxy resin to fix and seal the lead holes, forming an integrated thermocouple power semiconductor, ensuring the original sealing of the module is not compromised.

[0028] IV. Preparation of Infrared Radiation Window A power semiconductor with integrated thermocouples (using an IGBT module as an example) is selected. The chip surface has metal bonding wires for interconnection between chips and between the chip and the DBC copper layer, forming a complete current loop for the power semiconductor device. The bonding wires typically appear as an arch on the chip surface, with a height of approximately 3-4 mm. A cuboid mold is fabricated using common mold materials such as metal or ceramic (with a density slightly greater than that of the potting compound). The bottom dimensions of the mold are approximately equal to the length and width of the power chip, and the height is approximately 5 mm greater than the potting compound level. The power semiconductor is placed flat on a horizontal platform, and the mold is placed on top of the arch of the bonding wire at the center of the chip under test. The prepared potting compound is then injected into the cavity of the power semiconductor, and the two are moved into a vacuum chamber. The chamber is evacuated to below 0.01 Pa at room temperature for 30 minutes for degassing. The sample is then removed and placed in a constant temperature chamber for curing. After the potting compound has completely cured, the mold is removed, creating an infrared radiation window on the chip surface that is flush with the height of the metal bonding wire arch, serving as a "temperature measurement target area" for infrared measurement.

[0029] The prepared infrared radiation window region features a thin layer of potting compound on the power semiconductor chip surface (arch height 3mm-4mm). Metal bonding wires and diamond micropowder further enhance the thermal conductivity of the potting compound, enabling rapid heat transfer from the chip to the window potting compound surface within tens of milliseconds. Simultaneously, the chip surface exhibits low metal emissivity (<0.4). Previously, infrared thermometry required spraying a black organic coating onto the chip surface; however, the prepared infrared radiation window retains a thin layer of potting compound with high emissivity (≥0.90), allowing for direct infrared thermometry.

[0030] A commonly used potting compound for power semiconductor devices (taking polydimethylsiloxane as an example, component AB) was selected, and diamond powder with a particle size of W3-W5 micrometers was added to the potting compound. Appropriate amounts of potting compound and diamond were weighed separately using an electronic balance according to a predetermined mass fraction (the amount of diamond powder added accounts for 5%~20% of the mass of the potting compound). The weighed potting compound and diamond powder were transferred to a beaker and stirred for 20-30 minutes at room temperature and 3000 rpm using a magnetic stirrer. The potting compound-diamond powder mixture, along with the beaker, was transferred to a vacuum chamber and evacuated to below 0.01 Pa at room temperature for 30 minutes to remove the evacuation pressure. After evacuation, the mixture was removed and allowed to stand at room temperature for later use.

[0031] V. Infrared Module Integration A miniature infrared temperature measurement module (using an uncooled infrared sensor chip such as GD60914A) is selected, which has data sampling and transmission functions, a temperature measurement range of -40℃ to +250℃, a size of 29mm×29mm, a temperature measurement accuracy of ±2℃, and a pixel array of 80×62. A 10mm diameter through hole is pre-drilled at the corresponding position of the infrared radiation window on the IGBT module housing. The infrared probe of the miniature infrared temperature measurement module is inserted into the through hole, vertically aligned with the infrared radiation window, and the distance (L) between the probe and the infrared radiation window is adjusted so that the radiation window fills the probe's viewing window (L≤0.5D, where D is the lateral dimension of the infrared radiation window). After installation, the temperature measurement module is fixed to the module housing using screws or weather-resistant adhesive.

[0032] VI. Thermocouple Temperature Calibration The prepared power semiconductor device sample was placed in a constant temperature chamber for heating and insulation. Multiple temperature points were selected from room temperature to the device's maximum operating range (e.g., 30℃, 50℃, 70℃, 90℃, 110℃, 130℃, 150℃). Before testing at each temperature point, the sample was allowed to stand for at least 30 minutes, and the set temperature of the chamber and the thermocouple temperature measurement results were recorded simultaneously. Based on multiple sets of data, a calibration curve between the thermocouple temperature measurement results and the chamber temperature was plotted or fitted (e.g., ...). Figure 2 As shown in the figure, the temperature measurement system was calibrated. The test results show that the integrated thermocouple can track the temperature of the chamber well, with a measurement error within 1℃, which meets the measurement accuracy requirements.

[0033] VII. Infrared Module Temperature Measurement Calibration To obtain an accurate mapping relationship between the infrared temperature measurement and the actual chip surface temperature applied to the specific module in this embodiment, an infrared module temperature measurement calibration experiment was conducted. A low-voltage DC loading platform was used to conduct a constant current loading experiment on the fabricated power semiconductor device sample until thermal steady state. Simultaneously, integrated thermocouples and an infrared module were used to measure the chip surface temperature and the infrared radiation window temperature. The temperature difference between the thermocouple and the infrared module under different heat flux densities at thermal steady state was recorded, establishing a mapping relationship between the chip temperature and the infrared radiation window temperature, and calibrating the infrared module temperature measurement error. Figure 3 As shown in the figure. The calibration results show that the infrared temperature measurement value is slightly lower than the thermocouple temperature measurement value under different heat flux density conditions, with a fixed deviation of 1℃~3℃. Therefore, in actual use, the infrared temperature measurement value needs to be positively corrected by 1℃~3℃ to better match the actual temperature of the chip surface.

[0034] 8. Insulation withstand voltage test The insulation performance of the integrated thermocouple to the high-voltage circuit of the power semiconductor device is crucial to the reliability of the temperature measurement system. Therefore, insulation withstand voltage testing must be conducted to verify whether the integrated thermocouple's insulation withstand voltage performance meets the usage requirements. First, all terminals of the power device (including power terminals and auxiliary terminals) are short-circuited using metal wires. Then, the thermocouple leads and the power semiconductor device substrate are short-circuited and grounded using wires. An insulation withstand voltage tester is used to apply a high voltage between the power semiconductor device terminals and the substrate, with test conditions referring to the national or military standards for insulation withstand voltage testing of power semiconductor devices. For example, for a 1700V IGBT module, the requirement is that a 4000V, 50Hz AC voltage load for 1 minute should result in a leakage current not exceeding 5mA. The power semiconductor device sample with the prepared integrated thermocouple, under AC 4000V, 50Hz load for 1 minute, showed a terminal-to-substrate leakage current of approximately 1.62mA, which is less than the national standard requirement, indicating that the insulation withstand voltage performance of the prepared power semiconductor device integrated thermocouple meets the requirements.

[0035] IX. Verification of Online Monitoring Function During normal operation, power semiconductor devices undergo continuous high-frequency switching, resulting in rapid changes in power circuit voltage and current. Since integrated thermocouples and infrared modules are directly located inside the power semiconductor devices, there is a significant risk of electromagnetic interference (EMI). Therefore, it is essential to test the online temperature monitoring function of the integrated sensors under strong EMI conditions. A switching test platform was constructed, including a DC power supply, supporting capacitors, and an inductive load. The power semiconductor devices were continuously switched by drive control, and the switching test waveforms are shown below. Figure 4 As shown. Temperature curves of the integrated thermocouple and infrared module were acquired at a switching frequency of 1kHz and a bus voltage of 500V. Figure 5 As shown, the results indicate that the temperature acquisition waveform is smooth and free of glitches under high voltage and high frequency switching conditions, verifying that the prepared power semiconductor device integrated thermocouple has good online temperature measurement function under strong electromagnetic interference environment.

[0036] The above embodiments demonstrate that the contact and non-contact combined sensing method for online temperature monitoring of power semiconductor device chips described in this invention can achieve rapid, accurate, and reliable online measurement of chip junction temperature without affecting the electrical performance and packaging reliability of power semiconductor devices. Moreover, it is low-cost and has high engineering application value.

[0037] The power semiconductor chip temperature online monitoring system prepared by the above method includes: Contact temperature measurement unit: Composed of an insulated thermocouple array, used to directly measure the surface temperature of the chip; Non-contact temperature measurement unit: Composed of a miniature infrared module integrated into a plastic housing, used to measure the temperature of the infrared radiation window; Data processing unit: Built-in calibration model of chip temperature and infrared radiation window temperature, which corrects the output signal of the miniature infrared module in real time and verifies it with thermocouple measurement data; Insulation protection unit: Composed of potting compound and insulating encapsulation structure, it ensures the electrical safety of the system under high voltage environment.

[0038] The present invention features a contact thermocouple that is directly attached to the chip hot spot, with a measurement error within ±1℃; the non-contact infrared module achieves millisecond-level temperature response through a low-thickness, high-thermal-conductivity window, and combined with a calibration model, the error can be controlled within ±3℃, thus solving the problem of lag response of traditional thermistors.

[0039] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. Results show that the integrated infrared temperature measurement module can effectively monitor sub-second temperature fluctuation trends in power semiconductor device chips, meeting the requirements for online deployment.

Claims

1. A combined contact and non-contact sensing method suitable for online temperature monitoring of power semiconductor chips, characterized in that, Includes the following steps: 1) Thermocouple insulation encapsulation: The temperature sensing contact end of the thermocouple wire is inserted into the capillary tube, and the two ends of the capillary tube are sealed with insulating glue to form a thermocouple; 2) Determination of chip temperature measurement points: Establish an electrothermal coupled finite element model of power semiconductor, simulate and evaluate the chip temperature distribution under different heat flux densities, and mark the highest temperature position of each level chip as the temperature measurement point. 3) Chip surface thermocouple integration: Select an unencapsulated power semiconductor, pre-fabricate through holes on the plastic shell matching the number of temperature measurement points, attach one end of the thermocouple's temperature measurement contact to the temperature measurement point, and lead the other end of the thermocouple through the through hole and fix and seal it to form an integrated thermocouple power semiconductor. 4) Infrared radiation window preparation: A mold is placed on the top of the metal bonding wire arch on the surface of the integrated thermocouple power semiconductor chip and in the central area of ​​the chip. After the potting compound is injected and cured, the mold is removed to form an infrared radiation window that is flush with the height of the metal bonding wire arch. 5) Infrared module integration: The miniature infrared module is mounted on a plastic housing that integrates thermocouple power semiconductors, and the infrared probe of the miniature infrared module is vertically aligned with the infrared radiation window. 6) Thermocouple temperature calibration: The integrated thermocouple power semiconductor is placed in a constant temperature chamber, and the thermocouple is calibrated at multiple points within the range of room temperature to 150℃ to establish a mapping relationship between the thermocouple measured temperature and the constant temperature chamber set temperature. 7) Infrared module temperature measurement calibration: A low-voltage DC loading platform is used to carry out constant current loading experiments on the integrated thermocouple power semiconductor device until thermal steady state. The chip temperature measured by the thermocouple and the infrared radiation window temperature measured by the miniature infrared module are collected simultaneously to establish a calibration model of chip temperature and infrared radiation window temperature. 8) Insulation withstand voltage test: Perform insulation withstand voltage test between the terminals and the substrate of the integrated thermocouple power semiconductor to verify the insulation performance; 9) Online monitoring function verification: Under switching conditions, collect the window temperature data of the thermocouple and the calibrated miniature infrared module to verify the temperature measurement stability and anti-interference capability.

2. The method according to claim 1, characterized in that, In step 1), the diameter of the thermocouple wire is 0.25mm to 0.5mm, and the outer diameter of the capillary is less than 1mm and the inner diameter is slightly larger than the diameter of the thermocouple wire. Specifically, the temperature measuring contact end of the thermocouple wire is inserted from one end of the capillary, the temperature measuring contact extends to the other end of the capillary, and the distance from the temperature measuring contact to the other end of the capillary is 1 to 2mm. The thermocouple wire is a K-type thermocouple wire, the capillary tube is made of either quartz or high-purity alumina ceramic, and the insulating adhesive is an organosilicon insulating adhesive with a temperature resistance rating of ≥200℃.

3. The method according to claim 1, characterized in that, In step 2), the electrothermal coupling finite element model includes the chip, metal bonding wire, DBC substrate, potting compound and heat sink, and the simulation covers 50% to 120% of the rated operating heat flux density of the device; for multi-level topologies and multi-chip parallel power semiconductors, the highest temperature position of each level of parallel chip is marked.

4. The method according to claim 1, characterized in that, In step 3), the through hole is prefabricated on the side or top of the plastic shell. The diameter of the through hole is slightly larger than the outer diameter of the capillary. The temperature measuring contact is bonded with a high-temperature resistant and thermally conductive insulating adhesive, and the through hole is sealed with epoxy resin.

5. The method according to claim 1, characterized in that, In step 4), insulating high thermal conductivity particles are added to the potting compound, stirred evenly, and vacuum degassing is performed. The insulating high thermal conductivity particles are selected from one or more combinations of oxide ceramics, carbide ceramics, nitride ceramics, or diamond, with a particle size of W3~W5 micrometers. The amount of insulating high thermal conductivity particles added accounts for 5%~20% of the mass of the potting compound. In step 4), the mold density is greater than the density of the potting compound, the mold height is greater than the potting liquid level, the bottom surface is parallel to the chip surface, and the thickness of the infrared radiation window after potting and curing is 3mm~4mm, with an emissivity ≥0.

90.

6. The method according to claim 1, characterized in that, In step 5), the micro infrared module uses an uncooled infrared sensor chip; the distance between the infrared probe and the infrared radiation window satisfies L≤0.5D, where L is the distance between the infrared probe and the infrared radiation window, and D is the lateral dimension of the infrared radiation window.

7. The method according to claim 1, characterized in that, In step 6), there are no fewer than 7 calibrated temperature points, and the holding time for each calibrated temperature point is ≥20 minutes. After calibration, the thermocouple measurement error is within 1℃.

8. The method according to claim 1, characterized in that, In step 7), the calibration model is a linear relationship ΔT = a·T_chip + b, where ΔT is the difference between the chip temperature and the infrared radiation window temperature, T_chip is the chip temperature, and a and b are calibration coefficients. After calibration, the measurement error of the infrared module is within 3℃.

9. The method according to claim 1, characterized in that, In step 8), the loading conditions for the insulation withstand voltage test refer to the relevant national standards or military standards for power semiconductor devices. During the test, the power terminal and the auxiliary terminal are short-circuited, and the thermocouple lead is short-circuited and grounded to the integrated thermocouple power semiconductor substrate.

10. A power semiconductor chip temperature online monitoring system, characterized in that, Prepared using the method according to any one of claims 1 to 9, comprising: Contact temperature measurement unit: Composed of an insulated thermocouple array, used to directly measure the surface temperature of the chip; Non-contact temperature measurement unit: Composed of a miniature infrared module integrated into a plastic housing, used to measure the temperature of the infrared radiation window; Data processing unit: Built-in calibration model of chip temperature and infrared radiation window temperature, which corrects the output signal of the miniature infrared module in real time and verifies it with thermocouple measurement data; Insulation protection unit: Composed of potting compound and insulating encapsulation structure, it ensures the electrical safety of the system under high voltage environment.

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