Phase change heat transfer system for thermal management of metal oxide semiconductor field effect transistor and simulation detection method

Abstract

The invention relates to a phase change heat transfer system for metal oxide semiconductor field effect transistor thermal management and a simulation detection method, the system comprises a system container, the system container is provided with a plurality of fins, the plurality of fins form a first accommodating cavity and a second accommodating cavity, and the second accommodating cavity is provided with a third accommodating cavity; phase change materials are arranged in the first accommodating cavity and the second accommodating cavity, a metal oxide semiconductor field effect transistor is arranged in the third accommodating cavity, and the peripheral side walls and the bottom surface of the metal oxide semiconductor field effect transistor are wrapped by the third accommodating cavity; the scheme of the invention has the advantages that the PCM and the fins are added to improve the heat management potential, so that the heat dissipation performance of the chip is improved.

Description

Technical Field

[0001] The present application relates to the technical field of phase change materials, and in particular to a phase change heat transfer system and a simulation detection method for thermal management of a metal oxide semiconductor field effect transistor (MOSFET). Background Art

[0002] With the rapid development of science and technology, various electric drive devices and electrical systems are increasingly widely used in the field of industrial manufacturing. In the field of vehicle manufacturing, electric vehicles have been widely popularized in countries around the world. From 2010 to 2021, the number of electric passenger vehicles worldwide increased from 0.017 million to 16.267 million, and the electronic devices installed on vehicles are also developing rapidly. At present, power semiconductors in this field are mainly dominated by silicon-based insulated gate bipolar transistors (IGBTs) and metal oxide semiconductor field effect transistors (MOSFETs, MOSFET). However, these silicon-based semiconductors have inherent limitations such as high switching losses and limited switching speeds. The latest silicon carbide (SiC)-based semiconductor materials are considered to be high-performance semiconductor materials that may be widely used in the future due to their higher thermal conductivity, faster switching speeds and better high temperature resistance. For aerospace applications that always work in harsh environments, SiC-based power semiconductors have better voltage tolerance, faster response capabilities and better adaptability to extreme temperatures than ordinary silicon-based power semiconductors.

[0003] The study found that the failure rate doubles for every 10°C increase in chip temperature. The cooling methods of semiconductor modules are divided into air cooling, liquid cooling, phase change cooling and heat pipe cooling. For air cooling, the heat dissipation strategy of air cooling is not practical due to the poor working conditions of semiconductors. For example, in vehicle applications, semiconductor devices are installed in the engine compartment and the temperature may be as high as 150°C. In general, electronic equipment modules used in vehicles and aerospace are highly sealed. In terms of liquid cooling, due to the large system volume, additional energy supply is required, and most importantly, as an active cooling method, this cooling strategy requires additional maintenance, which is inconsistent with the needs of the aviation field with extremely high reliability requirements. Heat pipe cooling is an ideal heat dissipation strategy due to its high thermal conductivity and low temperature difference; however, due to its disadvantages such as high cost, easy clogging and limited size, it still has many limitations in practical use. For phase change cooling, the increase in temperature triggers the melting of the phase change material (PCM), resulting in a phase change. This process involves the absorption of a large amount of heat, which can effectively regulate the temperature. In practical applications, when electronic chips are running at high power and full load, their temperature rises rapidly as their heat flux increases. When the temperature rises to the phase change temperature of the PCM, the PCM absorbs heat through phase change, keeping the electronic chip at this temperature for a period of time. If the electronic chip only operates at a high power state for a short period of time, the PCM can effectively prevent the temperature of the electronic chip from reaching the threshold. This cooling strategy is compact and lightweight. At the same time, this passive cooling strategy has the advantages of low maintenance cost and low failure rate. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present application provides a phase change heat transfer system for thermal management of metal oxide semiconductor field effect transistors, which adds PCM and fins to improve the thermal management potential, thereby improving the heat dissipation performance of the chip.

[0005] In order to solve the above technical problems, the technical solution adopted in the present application is: a phase change heat transfer system for thermal management of metal oxide semiconductor field effect transistors, the system comprising a system container, a plurality of fins being arranged on the system container, the plurality of fins forming a first accommodating cavity and a second accommodating cavity, a third accommodating cavity being formed on the second accommodating cavity; phase change materials being arranged in the first accommodating cavity and the second accommodating cavity, a metal oxide semiconductor field effect transistor being arranged in the third accommodating cavity, and the side walls and bottom surface of the metal oxide semiconductor field effect transistor being covered by the third accommodating cavity.

[0006] By adopting the above scheme, the present application obtains a phase change heat transfer system with phase change material by accommodating phase change material in the system, which can effectively cool the metal oxide semiconductor field effect transistor through the performance of the phase change material, and has a simple structure, does not require a complex structure, and occupies a small volume; in addition, the present application arranges multiple fin structures in the system container, and then arranges the phase change material in the accommodating cavity formed by the fins, so that the phase change material can be fully and evenly distributed in the container, which can have a more ideal heat dissipation effect on the metal oxide semiconductor field effect transistor (MOSFETs, MOSFET) and improve its heat dissipation performance; and this fin structure can also allow more independent phase change materials to be placed in the container, further improving the heat dissipation performance.

[0007] Furthermore, the cross-section of the system container is square, rectangular or circular. The above structure can be used to accommodate the phase change material and give the system phase change material the ability to cool down. In addition, more importantly, the use of multiple shapes can improve the adaptation efficiency of the system and meet the needs of different usage environments.

[0008] Furthermore, the volumes of the system containers with square, rectangular or circular cross-sections are substantially the same (the volumes are substantially equivalent); adopting this solution can ensure that no matter what structure the system has, a stable occupied space can be maintained.

[0009] Furthermore, the cross-section of the system container is a rectangle. With this structure, the space utilization efficiency and the difference in ΔT are relatively small, and the system with a rectangular structure is more widely applicable in practical applications.

[0010] Furthermore, the metal oxide semiconductor field effect transistor is not in direct contact with the phase change material; specifically, the metal oxide semiconductor field effect transistor and the phase change material are isolated by fins, which can prevent the PCM from directly contacting the MOSFET during the phase change process and causing corrosion to the MOSFET.

[0011] Furthermore, the second accommodating chamber and the third accommodating chamber are arranged vertically and horizontally, and a copper sheet is arranged between the second accommodating chamber and the third accommodating chamber, and the copper sheet is located at the bottom of the metal oxide semiconductor field effect transistor; with this structure, the Cu sheet is placed between the PCM and the MOSFET, and its function is to prevent the corrosion of the MOSFET caused by the direct contact between the PCM and the MOSFET; at the same time, the Cu sheet can also more evenly transfer the heat generated by the MOSFET to the PCM and fins below it, thereby achieving effective heat dissipation.

[0012] Furthermore, the first accommodating cavity surrounds the circumference of the metal oxide semiconductor field effect transistor, and the second accommodating cavity is located below the metal oxide semiconductor field effect transistor; this structure can achieve full coverage of the phase change material and accommodate as much phase change material as possible to achieve a more ideal heat dissipation effect.

[0013] Furthermore, the material of the system container is one of Cu, Al or Ag.

[0014] Furthermore, the material of the system container is Cu, and the MOSFET / PCM system with copper as the frame material has the best thermal management capability.

[0015] Furthermore, the type of the PCM is one of RT69HC, RT70HC, RT80HC, and RT82.

[0016] Furthermore, the type of PCM is PCM-RT69HC, which can provide the best thermal management capability for the system.

[0017] The present application also provides a simulation test method for the phase change heat transfer system for thermal management of metal oxide semiconductor field effect transistors, the specific steps of which include:

[0018] (1) First, a 3D model of the MOSFET / PCM system is established using the MOSFET structure of the present application;

[0019] (2) Numerical model: When simulating the heating and cooling process of a MOSFET system containing PCM (phase change material), the principles of continuity, energy and momentum are considered; in addition, the CFD (computational fluid dynamics) simulation uses the Boussinesq approximation as its basis, and the equations governing continuity and momentum are given in equations (1-5):

[0020]

[0021]

[0022] Where S x , S y and S z represent the momentum source terms in the x, y, and z directions, respectively, which are appropriately tailored to consider the phase change process of convection; where u, v, and w represent the velocities in the x, y, and z directions, respectively; the variable t represents time, ρ represents density, P represents performance score, μ represents dynamic viscosity, g represents gravitational acceleration, β represents thermal expansion coefficient; T represents temperature, and constant A mushy , also called the mushy zone constant, ranges from 10 4to 10 7 between, used in ANSYS Fluent enthalpy porosity technology; in this context, A mushy The value of is chosen to be 10 5 , λ represents the liquid volume fraction, ε is a constant used to prevent division by zero in the equation; in this application, ε is assigned a value of 0.001;

[0023] The energy equation is given by formula (6):

[0024]

[0025] Among them, specific enthalpy H=h+ΔH, h represents the sensible enthalpy, while k represents the thermal conductivity. ΔH represents the latent heat content of the PCM, h ref and T ref are the reference enthalpy and reference temperature of PCM respectively. p represents specific heat capacity, L represents latent heat; considering that changes in operating temperature may trigger significant phase changes during the charging and discharging process of PCM, the liquid fraction λ is designed to vary with temperature according to a specific relationship, as shown below: If T PCM <T solidus ,λ=0. If T PCM >T liquidus ,λ=1. If T solidus <T PCM <T liquidus ,

[0026] (3) Simulation settings: In this numerical study, the CFD software ANSYS2022R2 was used to simulate the thermal behavior of the MOSFET system. The 3D model of the MOSFET system was established by the 3D modeling software SolidWorks 2022 and imported into ANSYS2022R2Workbench for meshing. In the simulation settings, transient simulation was selected to monitor the temperature change of the entire system during the MOSFET heating process in real time. Due to the existence of phase change process, energy was considered in the heat transfer model, and according to the previous assumptions, the viscosity model was configured for laminar conditions. In view of the inherent phase change process of PCM, the solidification and melting functions have been activated accordingly. In the solution stage of transient simulation, the PISO method was selected as the preferred solution strategy. For the finite volume method (FVM), a staggered grid layout was selected. For momentum and energy calculations, the second-order upwind scheme was used, while the PRESTO scheme was used to solve the pressure equation. In the solution control settings, relaxation factors have been assigned to various physical quantities.

[0027] Furthermore, the relaxation factors of pressure, density, body force, momentum, liquid fraction and energy involved in step (3) are set to 0.3, 1, 1, 0.7, 0.9 and 1 respectively; for the convergence criterion, the energy residual is set to 10 -6 , and all other residuals are set to 10 -4 as the threshold for reaching a satisfactory solution.

[0028] Advantages and beneficial effects of this application:

[0029] 1. The present application introduces phase change material and fin structure into MOSFET, and the slope of the temperature change curve of the MOSFET filled with PCM is significantly smaller. This is because PCM absorbs a large amount of latent heat of phase change and suppresses the rapid rise of temperature. Compared with the system without PCM, the integration of PCM shows a favorable effect in reducing the temperature difference inside the system. Therefore, PCM has the ability to effectively regulate the temperature during the phase change process of MOSFET heating simulation. In addition, by comparing with the experimental group without PCM, it can be proved that PCM can reduce the ΔT in the system. Therefore, the structure of the present application integrates PCM (phase change material) into the MOSFET / PCM system, which is of great significance to improving the heat dissipation efficiency of the system. Compared with the system without PCM filling, it not only reduces the overall temperature of the system, but also alleviates the temperature change within the system.

[0030] 2. The system of the present application adopts three systems of different shapes, showing that among the three shapes of MOSFET / PCM systems, the internal ΔT of the MOSFET in the circular system is the smallest, which is 12.44°C, the ΔT in the square system is in the middle, which is 12.54°C, and the ΔT of the rectangular system is the largest, which is 12.65°C, which is 1.69% larger than the smallest circular system; the order of ΔT of the three shape systems from small to large is consistent with the order of their side areas from small to large. Under almost the same volume, the average temperature (T avg ) up to 190°C, T of MOSFETs in round and rectangular systems avg The values ​​are almost the same, about 185°C. Although the circular system has the smallest temperature difference (ΔT), which is 12.44°C, the larger system side area may aggravate the ΔT within the system; however, compared with the circular system, the rectangular system has higher space utilization in actual use, and the relatively small difference in ΔT, so the rectangular system is more widely applicable in practical applications.

[0031] 3. The system of this application uses different types of PCM. In the MOSFET / PCM system, the T avghas a similar trend, which can be divided into three stages, depending on the slope mentioned above; in the first 1.5 minutes of the simulation, the four T avg The curves almost overlap in the first stage, that is, in this stage, the PCM is completely in the solid state, which means that the PCM has not yet started phase change and has not absorbed the latent heat of phase change; the contribution of the four different types of PCM to thermal management is very low, and the variables of the four experimental groups are almost negligible; entering the second stage, the T of the MOSFET in the four systems avg The curves begin to diverge, and the MOSFET using a PCM with a lower phase transition temperature has a lower T avg , PCM-RT69HC provides the best thermal management capabilities for the system.

[0032] 4. Four materials are used for the container of the system of the present application, among which the system using Cu as the frame material exhibits the lowest ΔT value of 12.18°C. It is closely followed by the Ag experimental group, whose ΔT is 12.2°C. Next, the ΔT of the MOSFET / PCM system using Al as the frame is 0.46°C higher than the previous one. The experimental group with Fe as the frame has the highest ΔT value, reaching 14.16°C, which is 16.26% higher than the lowest ΔT value observed in the Cu experimental group. This is also because Cu has better thermal conductivity and can more effectively prevent heat accumulation, thereby producing a smaller ΔT within the system. Therefore, due to Cu's excellent thermal management capabilities, Cu can be selected as the frame material of the MOSFET / PCM system in subsequent practical applications.

[0033] 5. In the simulation method of this application, SiC MOSFET is divided into different areas according to the different internal materials, and then the heating conditions of the internal areas of MOSFET are simulated using ANSYS software. At the same time, previous studies lack the research on the cooling system materials based on PCM and fins. At the same time, in this numerical study, the thermal management potential of adding PCM and fins in SiC MOSFET system is confirmed. On this basis, the article discusses in detail the influence of variables such as system shape, PCM with different thermophysical properties, fin material and heat transfer coefficient on the heat dissipation performance of SiC MOSFET system.

[0034] 6. The detection simulation method of the present application can screen out the phase change heat transfer system with the most ideal shape, structure and material, and provide a method for screening the phase change heat transfer system with more ideal heat dissipation performance, which can more conveniently and quickly obtain the phase change heat transfer system with ideal structure and material. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic structural diagram of a phase change heat transfer system with a square cross section in this application.

[0036] Figure 2 This is a schematic structural diagram of an exploded view of a phase change heat transfer system with a square cross section according to the present application.

[0037] Figure 3 This is a schematic structural diagram of a phase change heat transfer system with a rectangular cross section in this application.

[0038] Figure 4 This is a schematic structural diagram of an exploded view of a phase change heat transfer system of the present application, which has a rectangular cross section.

[0039] Figure 5 This is a structural schematic diagram of an axial cross-section of the phase change heat transfer system of the present application.

[0040] Figure 6 This is a schematic structural diagram of a phase change heat transfer system with a circular cross section in the present application.

[0041] Figure 7 It is a structural schematic diagram of an exploded view of a phase change heat transfer system of the present application with a circular cross section.

[0042] Figure 8 This is a schematic structural diagram of a phase change heat transfer system with a rectangular cross section in the present application without MOSFET.

[0043] As shown in the attached drawings: 1. system container, 101. fin, 2. first containing cavity, 3. second containing cavity, 4. third containing cavity, 5. phase change material (PCM), 6. metal oxide semiconductor field effect transistor (MOSFET), 7. copper sheet.

[0044] Fig. 9 T avg and changes in the liquid fraction of the PCM.

[0045] Fig.10 MOSFET system temperature contours with (a) and without (b) PCM filling.

[0046] Fig.11 Temperature difference (ΔT) of MOSFET system with and without PCM.

[0047] Fig.12 T inside MOSFET in three shape systems avg (a) Changes in the liquid fraction of PCM in the systems with three shapes.

[0048] Fig.13 Internal ΔT of MOSFET in rectangular, square and circular MOSFET / PCM systems.

[0049] Fig.14Variation of MOSFET average temperature with selected PCM (a) and associated PCM liquid fraction (b).

[0050] Fig.15 MOSFET T avg Variation with selected container material (a) and associated PCM liquid fraction (b).

[0051] Fig.16 Internal ΔT of MOSFET in MOSFET / PCM system with different frame materials. DETAILED DESCRIPTION

[0052] The following will combine the embodiments and drawings to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only preferred embodiments, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention;

[0053] It should also be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may also be another intermediate component, fixed through the intermediate component. When a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be another intermediate component at the same time. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be another intermediate component at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by technicians in the technical field of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0054] As attached Figure 1-7As shown, a phase change heat transfer system for thermal management of a metal oxide semiconductor field effect transistor of the present application is provided. The system comprises a system container 1, wherein the system container 1 is provided with a plurality of fins 101, wherein the plurality of fins 101 form a first accommodation cavity 2 and a second accommodation cavity 3, wherein a third accommodation cavity 4 is formed on the second accommodation cavity 3; a phase change material (PCM) 5 is provided in the first accommodation cavity 2 and the second accommodation cavity 3, wherein a metal oxide semiconductor field effect transistor (MOSFET) 6 is provided in the third accommodation cavity 4, wherein the side walls and the bottom surface of the metal oxide semiconductor field effect transistor 6 are surrounded by the third accommodation cavity 4; The three containing cavities 4 are covered; the phase change materials of different materials are prepared into a structure that is compatible with the container, and then placed in the corresponding container cavity; the metal oxide semiconductor field effect transistor of the present application can adopt commercially available structures of different models; the depth of the first containing cavity of the present application is greater than the depth of the second containing cavity and the third containing cavity, wherein the third containing cavity is used to place the MOSFET, and after the MOSFET is placed, its upper end is basically flush with the upper end surface of the first containing cavity; the second containing cavity and the third containing cavity are arranged vertically and horizontally, and are basically located in the center of the system container to improve the effective cooling of the internal MOSFET by the surrounding phase change material.

[0055] By adopting the above scheme, the present application obtains a phase change heat transfer system with phase change material and fin structure by accommodating phase change material in the system. The metal oxide semiconductor field effect transistor can be effectively cooled by the performance of the phase change material, and the structure is simple, does not require a complex structure, and occupies a small volume. In addition, the present application arranges multiple fin structures in the system container, and then arranges the phase change material in the accommodating cavity formed by the fins, so that the phase change material can be fully and evenly distributed in the container, which can have a more ideal heat dissipation effect on the metal oxide semiconductor field effect transistor (MOSFETs, MOSFET) and improve its heat dissipation performance. Moreover, this fin structure can also allow more independent phase change materials to be placed in the container, further improving the heat dissipation performance.

[0056] As attached Figure 1-7 As shown, the cross-section of the system container 1 described in the present application is square, rectangular or circular (i.e., the cross-section along the horizontal direction). The above structure can be used to accommodate the phase change material and give the system phase change material the ability to cool down. In addition, more importantly, the use of multiple shapes can improve the adaptation efficiency of the system and meet the needs of different usage environments.

[0057] As an example, the volume of the system container 1 described in the present application with a square, rectangular or circular cross-section is the same; adopting this solution can ensure that no matter what structure the system has, a stable occupied space can be maintained.

[0058] As attached Figure 6-7 As shown, as an example, the cross-section of the system container 1 described in this application is a rectangle. With this structure, the space utilization efficiency and the relatively small difference in ΔT are achieved, and the system with a rectangular structure is more widely applicable in practical applications.

[0059] As an example, the metal oxide semiconductor field effect transistor 6 described in the present application is not in direct contact with the phase change material 5; specifically, the metal oxide semiconductor field effect transistor and the phase change material are isolated by fins, which can prevent the PCM from directly contacting the MOSFET during the phase change process and causing corrosion to the MOSFET.

[0060] As attached Figure 2 , 4 -5 and 7-8, the second accommodating chamber 3 and the third accommodating chamber 4 described in the present application are arranged in alignment with each other up and down, and a copper sheet 7 is arranged between the second accommodating chamber 3 and the third accommodating chamber 4, and the copper sheet 7 is located at the bottom of the metal oxide semiconductor field effect transistor 6; with this structure, the Cu sheet is placed between the PCM and the MOSFET, and its function is to prevent the corrosion of the MOSFET caused by the direct contact between the PCM and the MOSFET; at the same time, the Cu sheet can also more evenly transfer the heat generated by the MOSFET to the PCM and fins below it, so as to achieve effective heat dissipation; the surface of the copper sheet is consistent with the size of the lower surface of the metal oxide semiconductor field effect transistor, which can effectively isolate the MOSFET from the PCM below it.

[0061] As attached Figure 2 , 4 As shown in Figures 7-8, the first accommodating cavity 2 described in the present application surrounds the circumference of the metal oxide semiconductor field effect transistor 6 (surrounding its four side walls), and the second accommodating cavity 3 is located below the metal oxide semiconductor field effect transistor 6; the copper sheet 6 covers the upper end surface of the second accommodating cavity 3, and effectively isolates the PCM in the second accommodating cavity 3 from the MOSFET in the third accommodating cavity 4; the use of this structure can achieve full coverage of the phase change material and accommodate as much phase change material as possible to achieve a more ideal heat dissipation effect.

[0062] As an example, the material of the system container 1 described in the present application is one of Cu, Al or Ag, that is, the system container 1 described in the present application is prepared by using one of the above materials. Figure 1-8 The structure of the system container is shown.

[0063] As a preferred example, the material of the system container 1 described in the present application is Cu. The MOSFET / PCM system using copper as the frame material has the best thermal management capability.

[0064] As an example, the type of PCM described in this application is one of RT69HC, RT70HC, RT80HC, and RT82.

[0065] As an example, the type of PCM described in this application is PCM-RT69HC, which can provide the best thermal management capability for the system.

[0066] As an example, the attached Figure 1-8 As shown, the first accommodating cavity described in the present application is divided into 14 small chambers by multiple fins 101, and the second accommodating cavity is divided into 5 small chambers by multiple fins 101, and each small chamber is filled with PCM matching its size; and the third accommodating cavity is a complete structure located directly above the second accommodating cavity, and its size is adapted to the MOSFET to facilitate the placement of the MOSFET therein.

[0067] The following is a method for performing detection simulation using the above system as a specific example, and the specific steps include:

[0068] (1) Establishing the three-dimensional structure of the system. In this numerical study, the internal structure of SiC MOSFET is established, and its 3D model is as follows: Figure 1-4 As shown, Figure 1-8 The structure of the MOSFET / PCM system is shown, Figure 1 It is a 3D model of a MOSFET / PCM system;

[0069] The container of MOSFET contains PCM (phase change material) and fin structure; even if the volume is the same, different shapes will affect its surface area; the shape of the container filled with PCM and the fins will affect the side area of ​​the entire system in contact with the environment, thereby affecting the thermal management ability of the entire system. Therefore, in the research of this application, rectangular, circular and square MOSFET / PCM systems with almost the same volume were used (the largest model is 2.4% larger than the smallest model), and their corresponding side areas are 2305.38mm 2 、2041.09mm 2 and 2275.44mm 2 ,like Figure 1 , 3 and 6.

[0070] (2) Numerical model: When simulating the heating and cooling process of the MOSFET system containing PCM (phase change material), we consider the principles of continuity, energy and momentum. In addition, the CFD (computational fluid dynamics) simulation is based on the Boussinesq approximation. The equations governing continuity and momentum are given in equations (1-5):

[0071]

[0072]

[0073] Where S x , S y and S z represent the momentum source terms in the x, y, and z directions, respectively, which are appropriately tailored to consider the phase change process of convection. where u, v, and w represent the velocities in the x, y, and z directions, respectively. The variable t represents time, ρ represents density, P represents performance score, μ represents dynamic viscosity, g represents gravitational acceleration, and β represents the coefficient of thermal expansion. T represents temperature; the constant A mushy , also called the mushy zone constant, ranges from 10 4 to 10 7 between, used in ANSYS Fluent for enthalpy porosity techniques. In this context, A mushy The value of is chosen to be 10 5 λ represents the liquid volume fraction and ε is a constant used to prevent division by zero in the equation. In this study, ε is assigned a value of 0.001.

[0074] The energy equation is given by formula (6):

[0075]

[0076] Among them, specific enthalpy H=h+ΔH, h represents the sensible enthalpy, while k represents the thermal conductivity. ΔH represents the latent heat content of the PCM, h ref and T ref are the reference enthalpy and reference temperature of PCM respectively; C p represents the specific heat capacity, and L represents the latent heat. Given that changes in operating temperature may trigger significant phase changes during the charging and discharging of PCMs, the liquid fraction λ is designed to vary with temperature according to a specific relationship, as shown below: If T PCM <T solidus ,λ=0. If T PCM >T liquidus ,λ=1. If T solidus <T PCM <T liquidus ,

[0077] (3) Simulation setup: In this numerical study, the CFD software ANSYS2022R2 is used to simulate the thermal behavior of the MOSFET system. The 3D model of the MOSFET system (e.g. Figure 1-8(as shown) was established by 3D modeling software SolidWorks 2022 and imported into ANSYS2022R2 Workbench for meshing. In the simulation settings, transient simulation was selected to monitor the temperature changes of the entire system during the heating process of MOSFET in real time. Due to the existence of phase change process, energy is considered in the heat transfer model, and according to the previous assumptions, the viscosity model is configured for laminar conditions. In view of the inherent phase change process of PCM, the solidification and melting functions have been activated accordingly. In the solution stage of transient simulation, the PISO method was selected as the preferred solution strategy. For the finite volume method (FVM), a staggered grid layout was selected. For momentum and energy calculations, the second-order upwind scheme was adopted, and the PRESTO (Presto) scheme was used to solve the pressure equation;

[0078] In the solution control settings, relaxation factors have been assigned to various physical quantities; specifically, the relaxation factors for pressure, density, body force, momentum, liquid fraction, and energy are set to 0.3, 1, 1, 0.7, 0.9, and 1, respectively. For the convergence criterion, the energy residual is set to 10 -6 , and all other residuals are set to 10 -4 as the threshold for reaching a satisfactory solution.

[0079] (4) Results and discussion

[0080] 4.1 Comparison of MOSFET / PCM systems with and without PCM

[0081] Before simulating the thermal management capabilities of a MOSFET / PCM system with different parameters, it is necessary to demonstrate that the introduction of the PCM has a positive impact on the heat dissipation capabilities of the entire system. Therefore, in this simulation stage, the thermal conductivity h is set to 5 W / m 2 K, and the material of the system container is set to aluminum (Al), and the rectangular MOSFET system filled with PCM-RT70HC and the system without PCM are tested at ambient temperature (T a ) was set to 25°C for MOSFET heating simulation. Fig. 9 a shows the average internal temperature of the MOSFET (T avg ) changes with time, and Fig. 9 b shows the liquid volume fraction of the PCM filled in the MOSFET / PCM system as the temperature increases during the simulation. Fig. 9 a. Regardless of whether PCM is filled in the MOSFET system, the temperature of the MOSFET increases as the heating simulation progresses. Maximum T of the built-in MOSFET in the experimental group containing PCM-RT70HC avgAt the end of the simulation (t = 7 min), it reaches 182.98°C. Meanwhile, the maximum T avg It is 90.09℃ higher than the former, reaching 273.07℃, a significant increase of 49.23% over the former. avg In addition to the difference in T avg The changes over time also show different characteristics. In the experimental group filled with PCM, the temperature curve is steep. Within about 1.5 minutes after the start of the heating simulation, the T avg It shows a clear upward trend and reaches a clear plateau at a time interval of about 2 minutes to 4 minutes. After that, the temperature curve continues to rise, similar to the previous 1.5 minutes, until it reaches 182.98℃ at the end of the simulation. Fig. 9 b shows the liquid volume fraction of the PCM phase change from solid to liquid. It can be found that within about the first 1.5 minutes of the simulation, the PCM did not start the phase change and remained in the solid state. This is because the heating temperature of the MOSFET has not yet reached the phase change temperature of the PCM-RT70HC. Therefore, during this period, the phase change material cannot effectively suppress the T avg Rise, corresponding to Fig. 9 The temperature in a rises rapidly at the same time. In about 2.5 minutes, Fig. 9 The phase change material in b undergoes a phase change, gradually changing from solid to liquid. During this process, a large amount of latent heat of phase change is absorbed, effectively controlling the T of MOSFET. avg , corresponding to Fig. 9 After that, because the phase change material completely changes phase and becomes 100% liquid, it can no longer absorb the latent heat of phase change, and its ability to suppress temperature rise is weakened, resulting in Fig. 9 The temperature curve in a rises significantly again. In the experimental group without PCM filling, T avg The curve is in the shape of an arc with a decreasing trend and reaches the highest average temperature of the MOSFET at the end of the heating simulation. Fig. 9 The two curves in a and analyze Fig. 9 From the PCM liquid volume fraction curve in b, it can be seen that during the time period before the PCM starts to change phase and the phase change is completed, that is, about 1.5 minutes before the start of the simulation and from 4 minutes to 7 minutes, the phase change material cannot effectively absorb the latent heat of phase change, so the temperature control ability is insufficient. Fig. 9 The slopes of the two curves in a are similar, indicating that there is no significant difference in the temperature control ability of the two experimental groups during these two time periods. The key factor determining the temperature difference observed at the end of the simulation is the phase change period of the phase change material, especially the period from 1.5 minutes to 4 minutes. During this period, Fig. 9The two Ts in a avg The slopes of the curves are very different. The slope of the temperature change curve of the experimental group filled with PCM is significantly smaller. This is because PCM absorbs a large amount of latent heat of phase change and suppresses the rapid rise of temperature. In order to more intuitively show the contribution of PCM to MOSFET temperature control, Fig.10 The MOSFET system temperature cloud diagram is shown at the seventh minute of the simulation. Fig.10 a and Fig.10 b, it can be found that Fig.10 Compared with b, Fig.10 The system temperature in a is much lower because the introduced PCM absorbs heat through phase change.

[0082] In addition to the MOSFET’s T avg , its internal lower ΔT also contributes to the service life of the system. Fig.11 The ΔT inside the MOSFETs in both simulation groups at the end of the simulation is shown. In addition to the T avg , whose internal ΔT also contributes to the service life of the system. Fig.11 The ΔT within the MOSFETs in the two simulation groups at the end of the simulation is shown.

[0083] according to Fig.11 , the integration of PCM shows a favorable effect in reducing the temperature difference within the system compared to the system without PCM filling. Therefore, it is speculated that PCM has the ability to effectively regulate the temperature during the phase change process of MOSFET heating simulation. In addition, by comparing with the experimental group without PCM, it can be proved that PCM is able to reduce ΔT within the system.

[0084] 4.2 Effects of different shape systems on MOSFET thermal management

[0085] Although the volume is basically the same, different system shapes will result in different heat transfer areas between the system and the external environment. In order to evaluate the impact of shape on the thermal management performance of the MOSFET / PCM system, MOSFET heating simulations were performed at 25°C using three systems with basically the same volume but different shapes (rectangular, circular, and square), using aluminum as the container material and the thermal conductivity set to 5 W / m 2 K, PCM type is selected as PCM-RT70HC. Fig.12 a shows the average internal temperature (T) of the MOSFET in thermal simulations for MOSFET / PCM systems with different shapes. avg ) changes with time, and Fig.12 b shows the melting state of the PCM filled in the MOSFET / PCM system as the temperature increases during the simulation.

[0086] from Fig.12 As can be seen in a, in the heating simulation, the T of the three MOSFET / PCM systems with different arrangement shapes avg The curves show similar trends. In general, the temperature curves can be divided into three stages according to different slopes. The first stage is the first 1.5 minutes after the simulation starts, when the temperature starts to rise from the initial 25°C. In this stage, the slope of the temperature curve is large, indicating that the temperature rises rapidly. At the end of this stage, the temperatures of the three experimental groups all reach about 70°C. Fig.12 From the PCM liquid volume fraction curve in b, it can be found that the reason for the rapid temperature rise in the first stage is that the temperature has not yet reached the phase change temperature of the PCM, so the PCM cannot effectively absorb heat to suppress the temperature rise. The second stage is from 1.5 minutes to 4 minutes of simulation. In this stage, the slope of the temperature curve is significantly lower than that of the first stage, and the rapid temperature rise is suppressed. At the end of this stage, the temperature of the circular and rectangular MOSFET / PCM systems is almost the same and lower than that of the square system. Fig.12 From the liquid volume fraction curve in b, it can be concluded that the main reason for the decrease in the temperature rise rate in this stage is that the PCM begins to undergo phase change and absorbs a large amount of latent heat of phase change, thereby suppressing the temperature rise. At the same time, in the circular and rectangular systems, the PCM takes longer to completely liquefy and absorb heat, which is longer than the square system. Therefore, in the second stage, the T of these two experimental groups is avg The third stage is from the end of the second stage to the end of the seventh minute simulation. In this stage, because Fig.12 The PCM in b is already 100% liquid, that is, the phase change has been completed and can no longer absorb the latent heat of phase change. Fig.12 The slopes of the three temperature curves in a all increase again, and the temperature rise speed accelerates. At the end of this stage, the MOSFET in the square MOSFET / PCM system has the highest T avg , which is 190°C. T of MOSFET in rectangular and circular MOSFET / PCM systems avg Almost the same, about 185℃, about 2.63% lower than the former. Fig.13The ΔT within the MOSFET in three different shape systems at t = 7 minutes is shown. It shows that among the three shapes of MOSFET / PCM systems, the internal ΔT of the MOSFET in the circular system is the smallest, which is 12.44°C, the ΔT in the square system is in the middle, which is 12.54°C, and the ΔT of the rectangular system is the largest, which is 12.65°C, which is 1.69% larger than the smallest circular system. The order of ΔT of the three shape systems from small to large is consistent with the order of their side areas from small to large. Therefore, a larger system side area may exacerbate the ΔT within the system. However, compared with the circular system, the rectangular system has higher space utilization in actual use, so in the following simulation, the rectangular MOSFET / PCM system will be selected.

[0087] 4.3. Impact of different types of PCM on thermal management of MOSFET / PCM system

[0088] After determining the shape of the MOSFET / PCM system, the effect of the PCM type on the system's thermal management capabilities was investigated. At this stage of the simulation, the MOSFET / PCM system using Al as the container material was fully populated with four different types of PCM (RT69HC, RT70HC, RT80HC, RT82). a When the temperature is 25℃ and the thermal conductivity is h=5, the heat generation of MOSFET is simulated. The average temperature T avg like Fig.14 As shown in a, Fig.14 b shows the liquid volume fraction of the PCM in the system.

[0089] according to Fig.14 a. In MOSFET / PCM systems using different types of PCM, the T avg has a similar trend, and this change is divided into three stages, depending on the slope mentioned above. Among them, in the first 1.5 minutes of the simulation, the four T avg The curves almost overlap in the first stage. This can be combined with Fig.14 b, that is, at this stage, the PCM is completely in the solid state, which means that the PCM has not yet started phase change and has not absorbed the latent heat of phase change. The contribution of the four different types of PCM to thermal management is very low, and the variables of the four experimental groups are almost negligible. Entering the second stage, the T avg The curves begin to diverge, and the MOSFET using a PCM with a lower phase transition temperature has a lower T avg .

[0090] 4.4. Effect of different container materials on the thermal management potential of MOSFET / PCM systems

[0091] In this phase, the container material of the MOSFET / PCM system is investigated based on the previously selected best performing phase change material (PCM). During the simulation phase, the ambient temperature T a The temperature was set to 25°C and the heat transfer coefficient h was set to 5 W / m 2 K, PCM-RT69HC is selected, and four system container materials (Fe, Cu, Al and Ag) are selected to perform heating simulation of MOSFET. The average temperature T of MOSFET avg like Fig.15 As shown in a, Fig.15 b shows the liquid volume fraction of the PCM in the system.

[0092] according to Fig.15 a, T of MOSFET in MOSFET / PCM system using different types of container materials avg The variation trends can be roughly divided into two categories. The first category is the MOSFET / PCM system using Cu, Al, and Ag as the container material. In this type of temperature variation curve, T avg The changing trend of the curve can be regarded as the three-stage model mentioned earlier, that is, in the non-phase change stage with a PCM liquid volume fraction of 100%, the slope of the curve is large and the temperature rises sharply. Entering the second stage, the PCM begins to change phase and enters the phase change temperature range from 100% solid to 100% liquid. avg The rising speed of T is suppressed, and a clear shoulder appears on the curve. Entering the third stage, the PCM is completely transformed into a 100% liquid state and can no longer effectively absorb latent heat, so the temperature rises rapidly again. Among the three stages, the experimental group using Ag as the container material always shows the highest T avg , and reached 212.51℃ at the end of the simulation, which is 25.07℃ higher than the experimental group using Cu as the main material, which has the best temperature control ability throughout the simulation. avg The curve trend is the MOSFET / PCM system using Fe as the mold material. avg The curve changes only in two stages, namely the first stage of a sharp rise in the first minute after the start of the simulation, and the second stage of a slight slowdown but still rapid rise. At the end of the first stage of this set of simulations, T avgIt almost reached the temperature at the end of the second stage of the first three groups of experiments, which is about 110°C. However, at the end of the simulation, the temperature reached a maximum value of 217.57°C, an increase of 16.06% compared with the experimental group using Cu as the material. However, this is different from the previous simulation results. In the previous simulation, the experimental group with the longest phase change time in the liquid volume fraction diagram tends to have the best temperature control ability. In the simulation of the container material, according to Fig.15 b) The time required to complete the phase transition. The MOSFET with the longest phase transition time in the Fe-based system has the highest T avg and the worst thermal management capabilities. Fig.16 The ΔT inside the MOSFET is shown.

[0093] according to Fig.16 As shown in the bar graph, the system using Cu as the frame material exhibits the lowest ΔT value of 12.18°C. It is closely followed by the Ag experimental group, whose ΔT is 12.2°C. Next, the ΔT of the MOSFET / PCM system using Al as the frame is 0.46°C higher than the previous one. The experimental group with Fe as the frame has the highest ΔT value, reaching 14.16°C, which is 16.26% higher than the lowest ΔT value observed in the Cu experimental group. This is also because Cu has better thermal conductivity and can more effectively prevent heat accumulation, resulting in a smaller ΔT within the system. Therefore, due to Cu's excellent thermal management capabilities, Cu was selected as the frame material for the MOSFET / PCM system in subsequent simulations.

[0094] Through the above system structure scheme and specific simulation detection method, it can be concluded that: in order to optimize the thermal management performance of the MOSFET / PCM system during heating and reduce the failure rate caused by high temperature, it is theoretically verified that it is necessary to integrate PCM (phase change material) into these systems to enhance the overall thermal management capability. This application evaluates the influence of system geometry, PCM properties, main structural materials and heat transfer coefficient on the thermal behavior of the MOSFET / PCM system; the results show that: integrating PCM (phase change material) into the MOSFET / PCM system is of great significance for improving the heat dissipation efficiency of the system. Compared with the system without PCM filling, it not only reduces the overall temperature of the system, but also alleviates the temperature variation within the system. At almost the same volume, the average temperature (T avg ) is the highest, reaching 190°C. T of MOSFET in round and rectangular systems avgThe values ​​are almost the same, about 185°C. Although the circular system has the smallest temperature difference (ΔT) of 12.44°C, the rectangular system is more widely used in practical applications considering the space utilization efficiency and the relatively small difference in ΔT. PCM with lower phase transition temperature has a better effect on T in MOSFET / PCM system. avg The PCM-RT69HC provides the best thermal management for the system. The MOSFET / PCM system using copper as the frame material has the best thermal management. At the end of the simulation, its T avg It is 187.44℃, and the temperature difference (ΔT) is 12.18℃.

[0095] Increasing the thermal conductivity coefficient can effectively relieve the thermal stress within the MOSFET / PCM system. Specifically, at the end of the simulation, a 15W / m 2 The system with the thermal conductivity coefficient K exhibits the lowest average temperature (T avg ), which is 162.92℃. This temperature is higher than the thermal conductivity coefficient of 5W / m at the end of the simulation. 2 The system with a K value of about 13.08% is lower than that of the system with a K value of about 13.08%, thereby highlighting the importance of improving thermal conductivity in improving thermal management performance; therefore, the system of the present application can effectively reduce the temperature, occupy a small space and have a simple structure, and through a specific simulation detection method, the most ideal system structure of the present application can be determined, providing a basis for subsequent specific applications.

Claims

1. A phase change heat transfer system for thermal management of metal oxide semiconductor field effect transistors, characterized in that: The system includes a system container, on which a plurality of fins are arranged, the plurality of fins form a first accommodating cavity and a second accommodating cavity, a third accommodating cavity is formed on the second accommodating cavity; phase change materials are arranged in the first accommodating cavity and the second accommodating cavity, a metal oxide semiconductor field effect transistor is arranged in the third accommodating cavity, and the side walls and bottom surface of the metal oxide semiconductor field effect transistor are covered by the third accommodating cavity.

2. The phase change heat transfer system for thermal management of metal oxide semiconductor field effect transistor according to claim 1, characterized in that: The cross section of the system container is square, rectangular or circular.

3. The phase change heat transfer system for thermal management of metal oxide semiconductor field effect transistor according to claim 2, characterized in that: The volumes of the system containers with square, rectangular or circular cross sections are substantially the same.

4. The phase change heat transfer system for thermal management of metal oxide semiconductor field effect transistor according to claim 3, characterized in that: The cross section of the system container is rectangular.

5. The phase change heat transfer system for thermal management of metal oxide semiconductor field effect transistor according to claim 1, characterized in that: The metal oxide semiconductor field effect transistor is not in direct contact with the phase change material.

6. The phase change heat transfer system for thermal management of metal oxide semiconductor field effect transistor according to claim 5, characterized in that: The second accommodating cavity and the third accommodating cavity are arranged vertically and aligned, a copper sheet is arranged between the second accommodating cavity and the third accommodating cavity, and the copper sheet is located at the bottom of the metal oxide semiconductor field effect transistor.

7. The phase change heat transfer system for thermal management of metal oxide semiconductor field effect transistor according to claim 6, characterized in that: The first accommodation cavity surrounds the circumference of the metal oxide semiconductor field effect transistor, and the second accommodation cavity is located below the metal oxide semiconductor field effect transistor.

8. The phase change heat transfer system for thermal management of metal oxide semiconductor field effect transistor according to claim 1, characterized in that: The material of the system container is one of Cu, Al or Ag; the type of the phase change material is one of RT69HC, RT70HC, RT80HC and RT82.

9. A simulation test method for a phase change heat transfer system for thermal management of a metal oxide semiconductor field effect transistor according to any one of claims 1 to 8, characterized in that: The specific steps include: (1) First, a 3D model of the MOSFET / PCM system is established based on the structure of the system container; (2) Numerical model: When simulating the heating and cooling process of the MOSFET system containing the PCM, the principles of continuity, energy and momentum are considered; in addition, the CFD simulation is based on the Boussinesq approximation, and the equations governing continuity and momentum are given in equations (1-5): Where S x , S y and S z represent the momentum source terms in the x, y, and z directions, respectively, which are appropriately tailored to consider the phase change process of convection; where u, v, and w represent the velocities in the x, y, and z directions, respectively; the variable t represents time, ρ represents density, P represents performance score, μ represents dynamic viscosity, g represents gravitational acceleration, β represents thermal expansion coefficient; T represents temperature, and constant A mushy , also called the mushy zone constant, ranges from 10 4 to 10 7 between, used in ANSYS Fluent’s enthalpy-porosity technique; in this context, A mushy The value of is chosen to be 10 5 , λ represents the liquid volume fraction, ε is a constant used to prevent division by zero in the equation; in this application, ε is assigned a value of 0.001; The energy equation is given by formula (6): Among them, specific enthalpy H=h+ΔH, h represents sensible enthalpy, while k represents thermal conductivity; ΔH represents the latent heat content of PCM, h ref and T ref are the reference enthalpy and reference temperature of PCM respectively; C p represents specific heat capacity, L represents latent heat; Given that changes in operating temperature may trigger significant phase changes during the charging and discharging of PCMs, the liquid fraction is designed to change with temperature according to a specific relationship, as shown below: If T PCM <T solidus ,λ=0; if T PCM >T ltquidus ,λ=1; if T solidus <T PCM <T liquidus , (3) Simulation settings: In this numerical study, the CFD software ANSYS2022R2 was used to simulate the thermal behavior of the MOSFET system. The 3D model of the MOSFET system was established by the 3D modeling software SolidWorks 2022 and imported into ANSYS2022R2Workbench for meshing; in the simulation settings, transient simulation was selected to monitor the temperature changes of the entire system during the MOSFET heating process in real time; due to the existence of phase change processes, energy was considered in the heat transfer model, and based on previous assumptions, a viscosity model was configured for laminar conditions; in view of the inherent phase change process of PCM, the solidification and melting functions have been activated accordingly; in the solution stage of the transient simulation, the PISO method was selected as the preferred solution strategy; for the finite volume method, a staggered grid layout was selected; for momentum and energy calculations, the second-order upwind scheme was adopted, and the PRESTO scheme was used to solve the pressure equation; in the solution control settings, relaxation factors have been assigned to various physical quantities.

10. The simulation test method of the phase change heat transfer system for thermal management of metal oxide semiconductor field effect transistor according to claim 9, characterized in that: The relaxation factors of pressure, density, body force, momentum, liquid fraction and energy involved in step (3) are set to 0.3, 1, 1, 0.7, 0.9 and 1 respectively; for the convergence criterion, the energy residual is set to 10 -6 , and all other residuals are set to 10 -4 as the threshold for reaching a satisfactory solution.

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