A simulation method for transient parameters and parasitic parameters of military IGBT modules
Through the finite element simulation method, a three-dimensional geometric model of the IGBT module is established, the transient temperature and stress field are calculated, and the parasitic parameters are simulated, which solves the parameter measurement problem of military IGBT modules in the design stage, and improves the switching performance and reliability of the module.
Patent Information
- Application Number
- CN202111226504.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-10-21
- Publication Date
- 2025-08-08
- Estimated Expiration
- 2041-10-21
AI Technical Summary
The prior art is difficult to accurately measure the transient parameters and parasitic parameters of military IGBT modules during the design stage, resulting in overshoot failure and low reliability of the module during the switching process.
The finite element simulation method is used to establish a three-dimensional geometric model of the IGBT module, and the transient temperature and stress fields are calculated through the Transient Thermal and Transient Structural modules, and the parasitic capacitance and inductance are calculated by combining the Q3D Extractor module to realize the simulation of the transient thermal resistance, stress distribution and parasitic parameters of the module.
Quickly and accurately extract key parameters of IGBT modules, optimize module structure, improve switching performance, reduce the risk of overshoot failure, and shorten R&D time.
Smart Images
Figure CN113935217B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of finite element simulation of semiconductor modules, and in particular to a method for simulating transient parameters and parasitic parameters of a military IGBT module. Background Art
[0002] IGBT modules are fully controlled, voltage-driven, composite power semiconductor devices combining BJTs and MOS transistors. They are widely used in weapon systems such as ship power supplies, missile launchers, tank control systems, and radar power supplies. Foreign military-grade and aerospace-grade IGBTs are prohibited from import into China. Domestic demand is met primarily through large-scale imports from companies like Infineon and Mitsubishi, which are then screened, resulting in a high degree of import dependence. Furthermore, most imported modules are industrial-grade and lack packaging designed to withstand the harsh environment of aerospace, resulting in low reliability.
[0003] The turn-on and turn-off parameters of military IGBT modules directly affect the module's switching speed and reliability under long-term service conditions in harsh environments. These parameters mainly include thermal resistance, stress, and parasitic parameters.
[0004] For high-power IGBT devices, most of the power applied to the device during operation is converted into heat, increasing the module's operating temperature. Thermal resistance refers to the resistance encountered by heat flow (power) as it flows through a thermal conductor (producing a temperature difference across the conductor). It is an intrinsic device parameter related to the material and structure, and determines the extent of the device's temperature rise. The thermal resistance of an IGBT module is typically considered as the junction-to-case thermal resistance from the chip to the device housing (the midpoint of the bottom surface). The calculation formula is as follows:
[0005]
[0006] T j is the chip junction temperature, T c is the device case temperature, and P is the dissipated power. The dissipated power can be read directly from the device. Therefore, the key to simulating the thermal resistance of a power device is to obtain the chip junction temperature (T j ) and the device package case temperature (T c ).
[0007] Transient stress is a measure of the mechanical impact of switching a module on and off, and it characterizes its switching performance. For brittle materials, the maximum stress during the switching process must be less than the fracture stress; for rigid materials, the accumulated plastic strain must be less than the fracture strain.
[0008] After the IGBT module is turned on, the gate-collector voltage U GE Starts to rise, at time t3, U GE Rising to the threshold voltage U GE(TO) , then the collector circuit I CThe collector current starts to rise, and the rise in current produces a current change rate At the same time, due to the stray inductance in the commutation path, U CE Rapid decline:
[0009]
[0010] When the IGBT module is turned off, due to the stray inductance in the commutation circuit, the collector-emitter voltage will overshoot. The maximum collector-emitter voltage is:
[0011]
[0012] When U CE，max Higher than the blocking voltage U CES The device will fail when Under the stray inductance L σ The larger the value, the easier it is to overshoot and fail during turn-on and turn-off.
[0013] Transient parameters are determined by the module's structure, materials, and circuit flow. Thermal resistance and parasitic resistance are measured through testing but cannot be determined during the design phase. Parameters such as local stress are difficult to measure through testing. Summary of the Invention
[0014] In order to overcome the shortcoming that IGBT modal transient parameters are difficult to test and measure, the present invention provides a method for simulating transient parameters and parasitic parameters of a military IGBT module.
[0015] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is:
[0016] The present invention provides a method for simulating transient parameters and parasitic parameters of a military IGBT module, comprising:
[0017] a. Create a geometric model of the multi-layer structure of the IGBT module in the Designer model. The geometric model includes the DBC substrate, chip, copper base plate, terminals, and leads.
[0018] b. Importing the geometric model into the Transient Thermal module, calculating the transient temperature field of the IGBT module during the turn-on process, and extracting the transient thermal resistance and steady-state thermal resistance during the turn-on process;
[0019] c. Import the temperature field simulation results of the Transient Thermal module into the Transient Structural module to calculate the thermal stress field changes when the IGBT module is turned on;
[0020] d. Import the geometric model into the Q3D Extractor module to calculate the parasitic capacitance between the upper and lower copper layers of the DBC substrate during the IGBT module turn-on process, as well as the parasitic inductance of each node in the model;
[0021] e. Importing the geometric model and the steady-state temperature distribution of step c into the TransientThermal module as initial values, calculating the transient temperature field when the IGBT module is turned off, and extracting the transient thermal resistance and steady-state thermal resistance when turned off;
[0022] f. Importing the transient temperature field simulation results of step d into the Transient Structural module to calculate the thermal stress field changes when the IGBT module is turned off;
[0023] g. Import the geometric model into the Q3D Extractor module, set the source and drain of each unit current flow, calculate the parasitic capacitance between the upper and lower copper layers of the DBC substrate during the IGBT module shutdown process, and the parasitic inductance of each node in the model.
[0024] Furthermore, in step b, the IGBT chip is used as a heat source, and the transient thermal resistance and steady-state thermal resistance of the IGBT chip are extracted.
[0025] Furthermore, the step b adopts a transient thermal module, and by setting different calculation sub-steps for the turn-on process of the IGBT module, the transient thermal resistance of the turn-on process is calculated quickly and accurately.
[0026] Furthermore, in step c, the temperature field of the entire turn-on process is imported into the Transient Structural module to calculate the transient stress field, thereby determining the stress concentration point during the use of the IGBT module.
[0027] Furthermore, both step d and step g simulate the parasitic inductance in direct current and alternating current simultaneously.
[0028] Furthermore, in step e, the steady-state temperature field distribution after the IGBT module is turned on is imported into the Transient Thermal module as an initial value, the IGBT chip is used as a heat source, and the transient thermal resistance and steady-state thermal resistance of the FRD chip during the shutdown process are calculated.
[0029] Furthermore, the step g calculates the parasitic parameters of each node of the geometric model and between nodes when the IGBT module is turned off, based on the current flow state when the IGBT module is turned off.
[0030] Furthermore, the chip includes an IGBT chip and an FRD chip.
[0031] Beneficial effects of the present invention:
[0032] According to the present invention, finite element simulation is used to extend the steady-state simulation of the IGBT module to transient simulation. The changes in the temperature and stress field of the IGBT module during the turn-on and turn-off processes are simulated to obtain the transient thermal resistance and stress distribution of the IGBT module. The parasitic parameters of the IGBT module are simulated to obtain the parasitic resistance, parasitic capacitance, and parasitic inductance. By analyzing the response of the IGBT module during the turn-on and turn-off processes and simulating the transient and parasitic parameters, key parameters can be quickly and accurately extracted for IGBT module turn-on and turn-off performance research, shortening research and development time.
[0033] According to one solution of the present invention, the existing transient simulation of thermal resistance is extended to transient simulation. By adopting transient temperature field simulation, the temperature correlation of key parameters such as chip thermal conductivity is considered, the grid is reasonably divided, and the simulation time is set in segments, which improves the simulation speed while ensuring the calculation accuracy in the initial stage. After the geometric model is established, the transient / steady-state thermal resistance of opening and closing can be obtained.
[0034] According to one solution of the present invention, a transient stress field simulation model is established, and the temperature simulation results are imported as initial values. Taking into account the plasticity and viscoplasticity of the material, the mechanical response of the module during the switching process is simulated to obtain the stress concentration points of the IGBT module, locate overstress failures, and provide simulation results support for the optimization of the IGBT module structure and failure analysis.
[0035] According to one solution of the present invention, Q3D Extractor simulation software is used to perform fast and limited calculations of parasitic resistance, parasitic capacitance, and parasitic inductance in the early stages of design, thereby reducing overshoot failures, shortening R&D time, and ensuring the turn-on and turn-off performance of IGBT module products. BRIEF DESCRIPTION OF THE DRAWINGS
[0036] Figure 1 A flowchart schematically illustrating a method for simulating transient and parasitic parameters of a military IGBT module according to an embodiment of the present invention;
[0037] Figure 2 A schematic diagram illustrating the geometric structure of an IGBT module in a method for simulating transient parameters and parasitic parameters of a military IGBT module according to an embodiment of the present invention is shown;
[0038] Figure 3 A schematic diagram illustrating the geometric structure of the copper layer on the chip and DBC of an IGBT module in a method for simulating transient parameters and parasitic parameters of a military IGBT module according to an embodiment of the present invention is shown;
[0039] Figure 4The figure schematically shows the geometric structure diagram of the DBC ceramic layer and the lower copper layer of the IGBT module in a method for simulating transient parameters and parasitic parameters of a military IGBT module according to an embodiment of the present invention. DETAILED DESCRIPTION
[0040] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.
[0041] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments cannot be described one by one here, but the embodiments of the present invention are not limited to the following embodiments.
[0042] One embodiment of the present invention addresses the concept of simulating transient and parasitic parameters of a military IGBT module. The method establishes a three-dimensional finite element geometric model for simulation, quantitatively calculates the physical processes of the IGBT module's transient turn-on process, and obtains the temperature and stress fields during the turn-on and turn-off processes. This allows key parameters, such as the IGBT module's transient thermal resistance and stress, to be acquired during the design phase. By calculating parameters such as the module's parasitic resistance, capacitance, and inductance, the method addresses the difficulty and time-consuming nature of measuring module parasitic parameters, enabling rapid and accurate support for modules under development.
[0043] The steps of the method for simulating transient parameters and parasitic parameters of military IGBT modules in this embodiment are as follows: Figure 1 shown.
[0044] (a) Construct a three-dimensional finite element geometric model for transient simulation.
[0045] The main structure of the above geometric model is as follows Figure 2 As shown, it includes a chip 1, a DBC substrate 2, a copper base plate 3, a terminal 4 and a lead 5. Figure 3 As shown, the chip 1 includes an IGBT chip 11 and an FRD chip 12. The IGBT chip 11 is the main heat source and generates heat when the geometric model of the IGBT module is switched on and off. The FRD chip 12 works when the geometric model of the IGBT module is switched off to prevent the current from damaging the IGBT chip 11. Figure 3 and Figure 4 As shown, the DBC substrate 2 includes an upper copper layer 21, a ceramic layer 22, and a lower copper layer 23, wherein the lower copper layer 23 has a stress relief ring 24. For the three-dimensional lead 5, the specific simulation process of constructing its model is to first construct a 3D curve and a circular cross section, and then form a three-dimensional entity through a sweep scan, and then form a lead array after the pattern, as shown in FIG. Figure 1 shown.
[0046] (b) Calculate the thermal resistance parameters of the IGBT module during the turn-on process in the Ansys transient thermal module. The specific process is as follows:
[0047] First, set the load and constraints: During IGBT module operation, IGBT chip 11 is turned on and generates heat, while FRD chip 12 is turned off. Set IGBT chip 11 as the heat source, and apply unit power to the chip in the internal heat generation. Heat is primarily removed through convection between the IGBT module baseplate and the heat sink, while convection between other surfaces and the air is also considered.
[0048] Next, set the mesh and material settings. In the transient thermal module, use the squrd and sweep methods for meshing. Sizing controls the mesh size, coarsening the mesh for the copper baseplate and refining the mesh for IGBT chip 11 and FED chip 12. Set material parameters in Engineer Data, taking into account the temperature dependence of silicon and copper, and setting the temperature-dependent variations of density, isotropic thermal conductivity, and heat capacity.
[0049] Finally, calculate and solve: set multiple calculation sub-steps for the IGBT module turn-on process in Analysis Setting, from 10 -5 s starts, 10 -4 s, 10 -3 s, 10 -2 s and 10 -1 s sets a substep each time until the transient temperature distribution stabilizes. By adjusting the maximum and minimum step sizes of each substep and controlling the duration of each step, the maximum temperature of the IGBT module and the temperature of the copper baseplate 3 directly below the chip are extracted. The temperature difference is divided by the power to calculate the transient thermal resistance and plot the transient thermal resistance against the time table. The value after the transient thermal resistance stabilizes is the steady-state thermal resistance.
[0050] (c) Calculate the stress response of the IGBT module during the turn-on process in the Ansys transient structural module.
[0051] First, set the loads and constraints: In the Workbench module, call the transient structural module, associate the results in transient thermal with the model in transient structural, and use the calculated transient temperature as the thermal load input. Constrain the deformation of the four corners of the IGBT module, use the same temperature field and step size, and calculate the thermal stress changes during the IGBT module turn-on process.
[0052] Next, set up the mesh and materials. Silicon and ceramics are brittle materials, so choose the elastic-plastic constitutive equation. Copper is a plastic material, so choose the rigid-plastic constitutive equation. Solder is a viscoplastic material, so choose the Anand constitutive equation. Enter the corresponding material parameter values in the engineeringdata module to perform a nonlinear stress field simulation.
[0053] Finally, the calculations and solutions are: extract the maximum stress values of each part of the IGBT module, identify stress concentration points, compare the maximum stress response of brittle materials during the IGBT module's on-state with the material's fracture parameters, and determine whether overstress fracture will occur. Compare the maximum stress of plastic materials during the IGBT module's on-state with the material's yield stress to determine the degree of plastic deformation.
[0054] (d) Calculate the parasitic capacitance, parasitic inductance, and parasitic resistance parameters of the IGBT module during the turn-on process in the Q3D extractor module.
[0055] First, set the load and constraint content: import the established geometric model into the Q3D extractor module, set the C, E, G and other mesh nodes in Nets (geometric model nodes) according to the circuit conduction relationship of the IGBT module turn-on process, and set the source and sink for each node.
[0056] Secondly, set the mesh and material content: set the material parameters for each layer structure in the Properties module, and set the mesh coarseness in Mesh operations.
[0057] Finally, perform the calculations: Enable the CG module, set its frequency, and calculate the parasitic capacitance of each net (geometric model node) and the parasitic capacitance between nets (geometric model nodes). Select the DC RL module and the AC RL module to obtain the parasitic parameters of each and the DC and AC RL modules under direct current and alternating current conditions.
[0058] (e) Calculate the thermal resistance parameters of the IGBT module during the shutdown process in the Ansys transient thermal module.
[0059] First, set the load and constraints: When the IGBT module is turned off, IGBT chip 11 stops working and generating heat, and FRD chip 12 blocks the current flowing to IGBT chip 11. Use the steady-state temperature distribution of the IGBT module calculated in step (b) as the initial value, set FRD chip 12 as the heat source, and use intern heat generation to load the chip with unit power. The remaining heat dissipation conditions are the same as during the turn-on process.
[0060] Secondly, set the mesh and material content: the mesh and material are consistent with the temperature field settings during the opening process.
[0061] Finally, calculate the solution: Set the step size to match the transient temperature field. Extract the maximum temperature of the FRD chip 12 and the temperature of the copper baseplate 3 directly below the chip. Divide the temperature difference by the power to calculate the transient thermal resistance of the IGBT module during shutdown. Plot the transient thermal resistance against the time table. The value after the transient thermal resistance stabilizes is the steady-state thermal resistance.
[0062] (f) Calculate the field changes of transient field stress during the IGBT module turn-off process in the Ansys transient stress module.
[0063] The temperature field of the IGBT module during the shutdown process is imported into the Ansys transient stress module as the initial value, and the rest of the stress field settings are consistent with the stress field settings of the IGBT module during the turn-on process in step (c).
[0064] (g) Calculate the parasitic capacitance, parasitic inductance, and parasitic resistance parameters of the IGBT module during the turn-off process in the Ansys Q3D extractor module.
[0065] First, set the load and constraints: import the established geometric model into the Q3D extractor module, set nodes such as C, E, and G in Nets according to the conduction relationship or current flow state of the circuit in the IGBT module during the shutdown process, and set the source and sink for each node.
[0066] Secondly, set the mesh and material content and calculate the solution: consistent with the settings of the parasitic parameter simulation of the IGBT module turn-on process in step (d).
[0067] The above description is merely one embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.
Claims
1. A method for simulating transient parameters and parasitic parameters of a military IGBT module, comprising: a. Create a geometric model of the multi-layer structure of the IGBT module in the Designer model. The geometric model includes the DBC substrate, chip, copper base plate, terminals, and leads. b. Importing the geometric model into the Transient Thermal module, calculating the transient temperature field of the IGBT module during the turn-on process, and extracting the transient thermal resistance and steady-state thermal resistance during the turn-on process; c. Import the temperature field simulation results of the Transient Thermal module into the Transient Structural module to calculate the thermal stress field changes when the IGBT module is turned on; d. Import the geometric model into the Q3D Extractor module to calculate the parasitic capacitance between the upper and lower copper layers of the DBC substrate during the IGBT module turn-on process, as well as the parasitic inductance of each node in the model; e. Importing the geometric model and the steady-state temperature distribution of step (c) as initial values into the TransientThermal module, calculating the transient temperature field when the IGBT module is turned off, and extracting the transient thermal resistance and steady-state thermal resistance when turned off; f. Importing the transient temperature field simulation results of step (d) into the Transient Stress module to calculate the thermal stress field changes when the IGBT module is turned off; g. Import the geometric model into the Q3D Extractor module, set the source and drain of each unit current flow, calculate the parasitic capacitance between the upper and lower copper layers of the DBC substrate during the IGBT module shutdown process, and the parasitic inductance of each node in the model.
2. The simulation method according to claim 1, wherein: The step (b) uses the IGBT chip as a heat source and extracts the transient thermal resistance and steady-state thermal resistance of the IGBT chip.
3. The simulation method according to claim 2, wherein: The step (b) uses a transient thermal module to quickly and accurately calculate the transient thermal resistance of the turn-on process by setting different calculation sub-steps for the turn-on process of the IGBT module.
4. The simulation method according to claim 1, wherein: The step (c) imports the temperature field of the entire turn-on process into the Transient Structural module to calculate the transient stress field and determine the stress concentration point during the use of the IGBT module.
5. The simulation method according to claim 1, wherein , step (d) and step (g) both simulate the parasitic inductance in DC and AC simultaneously.
6. The simulation method according to claim 1, wherein: The step (e) imports the steady-state temperature field distribution after the IGBT module is turned on as the initial value into the Transient Thermal module, uses the IGBT chip as the heat source, and calculates the transient thermal resistance and steady-state thermal resistance of the FRD chip during the shutdown process.
7. The simulation method according to claim 1, wherein: The step (g) calculates the parasitic parameters of each node of the geometric model and between nodes when the IGBT module is turned off, based on the current flow state when the IGBT module is turned off.
8. The simulation method according to claim 1, wherein: The chips include an IGBT chip and an FRD chip.