High Power Insulated Gate Bipolar Transistor Research Articles

Thermal and energy performance characteristics of spiral-wing pin-fin heatsinks for liquid cooling of electronic devices in electric vehicles

Insulated gate bipolar transistors (IGBTs) are crucial components of electric vehicles (EVs) that regulate power. Liquid cooling has emerged as a cooling solution for high-power IGBTs in EVs. Although several pin-fin heatsinks (PFHs) have been developed to enhance cooling performance, comprehensive research on PFHs for IGBTs under liquid-cooling conditions is limited. This study investigated the cooling performance improvement of spiral-wing pin-fin heatsinks (SWPFHs) against conventional PFHs under liquid-cooling conditions. Using the developed simulation model, the optimal design of the SWPFH was determined to achieve the maximum Webb efficiency, which indicates the heat transfer capacity at the same power consumption. Furthermore, the heat transfer performance of the optimized SWPFH was compared with those of conventional PFHs with circular, square, and hexagonal pin-fin heatsinks under practical Reynolds numbers. The optimized SWPFH exhibited the lowest maximum temperature and standard temperature deviation among the conventional PFHs. The Webb efficiency of the optimized SWPFH was 21.9% higher on average than that of the conventional circular pin-fin heatsink (CPFH) owing to the enhanced mixing effects with the reduced wake region. Overall, the use of SWPFH for cooling IGBTs in EVs is recommended to improve the thermal performance of the CPFH under the same pumping power.

Thermal and electrical evaluation of insulated gate bipolar transistor (IGBT) power modules

The thermal reliability of two different high-power insulated gate bipolar transistor (IGBT) modules was studied under both conduction and switching regimes by experimental and numerical approaches. Indeed, the reliability of semiconductor devices is tightly linked to the junction temperatures reached in the IGBT, which is a function of the diode chips present in such devices and its operating condition. However, measurements of the semiconductor temperatures are often difficult to be done, thus requiring modeling and simulation tools to accurately evaluate the instantaneous temperature under different thermal loads. For this reason, a transient 3D heat transfer numerical model of two different IGBT power devices was proposed using the Finite Element Method, assuming that heat is dissipated on the IGBT by natural convection and radiation. These simulations were validated with experimental measurements, obtained through infrared thermography, performed for the IGBT modules either opened or enclosed, varying the heat source, the module orientation and under conduction or switching regime. For the switching regime, power losses due to the gate-closing and gate-opening transitions between conducting and non-conducting states were taken into consideration. The heat losses were modeled assuming the time-dependent heat dissipation obtained by previous electrical simulations, and it was compared with time-averaged heat source solutions. Results showed that averaging the heat source can significantly reduce the computational time, allowing quick design explorations. Overall, the numerical model led to deviations of less than 16% over the transient heating and at steady-state. Finally, the impact of a heat sink attached to the IGBT was studied, demonstrating that the proposed model can be used for accurate and quick investigations of potential failures and for the development of more efficient IGBT devices.

Thermo-sensitive electrical parameters of high-power IGBTs based on gate-emitter voltage measurement during switching delay intervals

High-power insulated gate bipolar transistors (IGBTs) are widely used for wind power conversion and electric traction. Accurate estimation of IGBT junction temperature and active thermal control improve the reliability of power converters in such applications. Among the various available methods for junction temperature estimation, thermo-sensitive electrical parameter (TSEP) based estimation is simple, fast and amenable to real-time implementation. Evaluation of many TSEPs (e.g. forward voltage, threshold voltage, peak dv/dt, peak di/dt etc.) require measurement of multiple electrical quantities in the power circuit and/or in the gate-drive circuit. The measurement systems need to have high precision and/or high bandwidth as well. Moreover, the quantities in the power circuit require isolated measurement systems. This paper explores possible new TSEPs, that could be obtained through a single measurement of low-voltage quantity, namely, the gate-emitter voltage. Since the gate-emitter voltage varies primarily during turn-on and turn-off delay intervals, these switching intervals and their parameters are studied over a wide range of operating conditions. Since many practical converters are expected to operate at an ambient temperature as low as −35 °C, the experimental study is carried out over a wide temperature range from −35 °C to 125 °C. Further, to ensure wider applicability of the findings of the study, four IGBTs of different makes are considered for the experimental investigations. The experimental results bring out four different parameters pertaining to turn-on delay and another four parameters pertaining to turn-off delay, which are potential TSEPs. Of these eight TSEPs, five of them can be evaluated based on measurement of gate-emitter voltage only, and four of these have not been reported in the literature previously. In addition, the experimental data are useful for development of temperature-sensitive device models for simulation, performance assessment and design of gate-drive circuit for different temperatures, and for temperature-sensitive compensation of inverter dead-time effect.

Multi-physics coupling analysis of high-power IGBT module bonding wires fault considering stray inductance of main circuit

The insulated gate bipolar transistor (IGBT) module is subjected to unbalanced electric-thermal stress for a long time due to its own turn-on and turn-off, the fluctuation of processing power and the change of external operating environment, resulting in fatigue failure. And there is a strong coupling effect between its electrical, temperature and mechanical properties. At the same time, the fatigue failure of IGBT module is also the result of multi-physical field coupling. This paper reveals the influence mechanism of main circuit stray inductance on the electric-thermal-stress coupling characteristics of high power IGBT module bonding wires fault in the context of mine-used inverter application. First, the inverter main circuit topology model considering stray inductance is constructed, and the loss value of the power chip is obtained based on extracting the busbar stray inductance and establishing the IGBT module behavior model, and the validity of the results is verified. Secondly, the package structure model of IGBT module is established and the failure analysis boundary conditions are determined, and then the joint circuit-finite element method is used to reveal the operation behavior characteristics of IGBT module under the combined action of multi-physical fields. Finally, the influence of main circuit stray inductance on the multi-physical field coupling characteristics of IGBT module and its change law are compared and analyzed under the bonding wires fault condition to study the causes of fatigue failure of IGBT module.

Dynamic IGBT Three-Dimensional Thermal Network Model Considering Base Solder Degradation and Thermal Coupling Between IGBT Chips

With the development of power electronic technology, the thermal characteristics of high-power insulated gate bipolar transistor (IGBT) module are vital information for thermal management of power electronic equipment, reliability analysis, and thermal design of power electronic system. However, the present commonly used lumped thermal network model based on thermal resistance and heat capacity still has some limitations in accurately predicting the junction temperature of IGBT modules, significantly once considering the degradation of base solder in high-power IGBT modules. In this paper, the thermal behavior of high-power IGBT chips under different base solder degradation is studied by the finite element method (FEM). The results show that the degradation of the base solder has effects on the thermal impedance between the junction and the case, which should be fastidiously thought about within the thermal network model modeling. As a result, a dynamic three-dimensional thermal network model that takes into account the thermal interaction between IGBT chips, as well as the degradation of the base solder, is proposed in this paper. The proposed thermal network model can estimate the junction temperature of a high-power IGBT module correctly and fast based on the real degradation of the base solder. Finally, finite element simulation and experimental findings are used to validate the proposed dynamic three-dimensional thermal network model. The results show that the dynamic three-dimensional thermal network model has comparable accuracy to finite element simulation and test results. At the same time, the dynamic three-dimensional thermal network model responds faster than the finite element simulation.

Warping model of high-power IGBT modules subjected to reflow soldering process

High-power insulated gate bipolar transistor (IGBT) modules are the key devices for energy change and transmission. Reflow soldering process is a crucial process in IGBT module packaging manufacture. Residual stress and warpage of IGBT modules are induced after soldering, which can lead to degradation of device performance and working life. Combining frame-based baseplate and the key material properties of AlSiC at different temperatures, latent heat and viscoplastic intrinsic models of the solder, this study established a finite element (FE) model of the reflow soldering process of IGBT modules to predict the warpage and residual stresses. Reflow soldering experiments of IGBT modules were conducted to examine the shape of the lower surface of the baseplate before and after the soldering process, and are used to verify the modeling results. The model shows a good agreement with the experimental with an error of 5.46%. The FE model will contribute to the optimization of reflow soldering process and package structure of IGBT module.

A Novel IGBT Junction Temperature Detection Based on High-Frequency Model of Inductor Element

Accurate online junction temperature detection of high-power insulated gate bipolar transistor (IGBT) modules is necessary for the health management system of key equipment. The voltage rise time ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$t_{\mathrm {rv}}$ </tex-math></inline-formula> ) is a good temperature sensitive electrical parameter (TSEP), which is of great significance for its accurate online extraction. In this article, a novel IGBT junction temperature detection based on the high-frequency (HF) model of inductor element is proposed. First, the equivalent model of the inductor element in the application circuit at HF is demonstrated. Second, based on the HF model of the inductor element, it is proposed and verified that <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$t_{\mathrm {rv}}$ </tex-math></inline-formula> in the IGBT turn-off process is consistent with the HF current pulse signal on the inductor element at HF, that is, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$t_{\mathrm {rv}}$ </tex-math></inline-formula> can be indirectly obtained by extracting the HF current pulse signal. Finally, the feasibility for voltage rise time extraction and junction temperature detection through HF isolation coil is verified by experiments and simulations. The research work in this article is helpful to the online junction temperature detection and has certain theoretical significance and practical engineering value.

Numerical simulation and optimization of heat dissipation structure for high power insulated gate bipolar transistor (IGBT)

With the increasing integration level of IGBT components, heat dissipation capacity determines whether its working state is stable. The third-generation semiconductor chips are expected to be made of SiC or GaN materials, with lower power loss and higher thermostability. Currently, the widely used backplane heat dissipation schemes cannot meet the heat dissipation requirements of high-power IGBT modules. In this study, an aluminium alloy shell with an AlN column is proposed to replace the traditional plastic shell to further improve the heat dissipation of IGBT devices. 180°C is set as the expected maximum temperature of the module, and finite element modelling and analysis of the heat dissipation structure of the IGBT device is carried out. Four types of design schemes are compared and the heat dissipation structure is optimized. AlN heat-transfer blocks and Ag sintering are introduced to realise the novel design. The results show that traditional single-side heat dissipation can not meet the requirements. The improved double-side dissipation scheme meets the requirement when the heat sink fin height is more than 15mm. And the optimized heat sink shall have 14 fins of 20mm in height. The results of this study can provide a reference for the thermal management and design of high-power third-generation semiconductor devices.

Independent closed loop control of di/dt and dv/dt for high power IGBTs

As the insulated gate bipolar transistor (IGBT) modules have their own specific characteristic switching forms, their turn-on and turn-off times are changed according to practical applications. For the conventional gate drives, gate resistors are used to adjust the turn-on and turn-off times which change switching losses that have a significant amount in total losses. Collector current rate of change, $di_{C}/ dt$ and collector-emitter rate of change, $dv_{CE}/ dt$ are dependent on each other and they affect operating parameters in high power converters. Relations between current and voltages during the switching transitions are given and effects of the changes in electrical parameters for the operation of IGBT are described. Thereafter, closed-loop gate drive with analog control that performs independent control of $di_{C}/ dt$ and $dv_{CE}/ dt$ of a new generation IGBT module platform for high power applications is proposed. Unlike conventional gate drives, proposed closed-loop drive makes constant $di_{C}/ dt$ possible while $dv_{CE}/ dt$ is decreased to increase the efficiency of the power conversion system. This leads to decrease of the switching losses without changing the electromagnetic interference (EMI), IGBT voltage, and current stresses which are related with the rate of change of collector current. Simulations are performed in a double pulse test circuit in which new package next high power density dual (nHPD$^{2}$) family MBM450FS33F Hitachi dual IGBT with 3300V 450A ratings is modelled.

Analysis of Reverse Recovery Characteristics of Anti-parallel Diode

Insulated gate bipolar transistor (IGBT) is widely used in various renewable green energy systems such as wind power generation and solar power generation at present. High-power IGBT modules usually include IGBT chips and anti-parallel diodes, and the transient characteristics of anti-parallel diodes will affect the external port characteristics of IGBT modules. Based on semiconductor physics and diode basic structure, this paper analyzes four stages of diode reverse recovery process, and describes the change process of turn-off time and stored charge by a step recovery process. Finally, the voltage and current waveforms of diode reverse recovery process are simulated and verified for a certain IGBT module.

Failure analysis and lifetime assessment of IGBT power modules at low temperature stress cycles

Lifetime models of high-power Insulated Gate Bipolar Transistors modules express the number of cycles to end of life as a function of stress parameters. These models are normally developed based on experimental data from accelerated power-cycling tests performed at predefined temperature stress conditions as, for example, with temperature swings above 60 °C. However, in real power converters applications, the power modules are usually stressed at temperature cycles not exceeding 40 °C. Thus, extrapolating the parameters of lifetime models developed using data from high-temperature stress cycles experiments might result in erroneous lifetime estimations. This paper presents experimental results from power cycling tests on high-power Insulated Gate Bipolar Transistors modules subjected to low temperature stress cycles of 30 and 40 °C. Therefore, devices experience still accelerated aging but with stress conditions much closer to the real application. Post-mortem failure analysis has been performed on the modules reaching end-of-life in order to identify the failure mechanism. Finally, the number of cycles to end-of-life obtained experimentally is fit with a state-of-the-art lifetime model to assess its validity at low temperature stress cycles. Challenges and limitations on data fitting to this lifetime model and the impact of various stress parameters on the anticipated failure are also presented.

A bio-inspired, low pressure drop liquid cooling system for high-power IGBT modules for EV/HEV applications

Thermal management of high power density insulated gate bipolar transistors (IGBTs) using a low pumping power is crucial for the development of high-performance electric vehicles (EVs) and hybrid electric vehicles (HEVs). In the present work, the liquid cooling module inspired by a human respiratory system was developed to provide enhanced thermohydraulic performance. The suggested cooling module consists of a multiscale flow manifold connected to a metal foam layer bonded to the bottom substrate of IGBT module. The unique flow path uniformly distributes the coolant to multiple IGBTs with minimizing the required pumping power, while maximizing the heat exchange area. The porosity of the metal foam was determined considering the conflict between the conductive and convective heat flux. The developed cooling module was applied to the single IGBT module, including 6 IGBT/diode pairs generating 1.55 kW of heat. The proposed cooling module provided a low (0.2 K/W) thermal resistance using only ~2 kPa of the pressure drop that is approximately 10 and 100 times lower than that of previously reported turbulator and microchannel systems, respectively. Even when the number of IGBT/diode pairs is increased from 6 to 24 (single to quadruple IGBT modules), only ~8 kPa of the pressure drop was required, which shows the high scalability of the proposed solution. This work will help develop a compact, low pumping power cooling solution for high-performance EV/HEV applications.

Detection of Transient Junction Temperature Characteristics of High Power IGBT

In this paper, Insulated Gate Bipolar Transistor (IGBT), which is the most widely used full-control power electronic device, is taken as the research object. Under the special working mode of short-time intermittent pulse, with the increase of conduction current, the chip junction temperature of high-power IGBT will rise sharply and fluctuate greatly, causing the operating characteristics of the device to be greatly affected by temperature. The commonly used method of measuring the bottom plate shell temperature with thermocouples and then estimating the steady junction temperature can no longer meet the demand. Firstly, the fluctuation characteristics of junction temperature of high-power IGBT are analyzed. Then, a high-speed infrared thermal imaging device is used to carry out real-time junction temperature detection. The distribution and rising process of instantaneous junction temperature on the chip surface are obtained, which further verifies the correctness of theoretical analysis. The research has important guiding significance for IGBT application design under short-time intermittent pulse operation mode, and also has certain reference value for general operation mode.

A Self-Regulating Gate Driver for High-Power IGBTs

To gain accurate control of the whole switching transients, this article proposes a self-regulating voltage-source gate drive (SRVSD) method for high-power insulated gate bipolar transistors (IGBTs) working under hard switching conditions. The SRVSD has a high-speed circuit capable of adjusting drive levels. With high-speed feedbacks, the on-board field programmable gate array (FPGA) identifies each switching stage and accordingly varies drive voltages. In this way, switching delay, diC/dt and dvCE/dt are regulated individually. The SRVSD allows accelerated delays and dvCE/dt stages without increasing diC/dt. Based on their principles, SRVSD is compared with existing active drivers comprehensively to verify its delay and loss reductions performance. By experiments, compared to conventional gate drive (CGD), SRVSD achieves at most 80%, 72% reductions in turn-on and turn-off delays, and 58%, 31% reductions in turn-on and turn-off losses at identical current/voltage overshoots. Moreover, the proposed adaptive control concept is verified in this article. Within several cycles, this concept automatically regulates durations of all delay, diC/dt and dvCE/dt stages to reach individual target values, largely independent of switching conditions. A practical piecewise linear switching-based loss model is proposed. Combined with SRVSD, this practical loss model can offer convenient sensing and control of switching losses in an accurate and online manner.

Limitations and Guidelines for Damage Estimation Based on Lifetime Models for High-Power IGBTs in Realistic Application Conditions

Statistical lifetime models for high-power insulated-gate bipolar transistors (IGBTs) are developed based on results from power-cycling experiments and relate lifetime expectancy to the well-defined conditions of a laboratory experiment. In most cases, predefined cyclic-stress conditions are repeatedly applied until the power device under test reaches its end of life. However, in real applications, power modules are exposed to nonrepetitive stress patterns that can be very different from the power-cycling conditions. A well-established lifetime estimation method suggests decomposing the stress pattern into individual components, whose damage can be calculated using a lifetime model. These damage contributions are then summed up in order to estimate the consumed or the remaining lifetime of a device. When comparing the estimation results to field measurements though, they often fail to match the real behavior of a power device. This article points out the uncertainties that appear in this process of applying a lifetime model on stress patterns deriving from field applications. The main purpose is to present typical sources of errors and discuss how severely these may impact the lifetime estimation.

An improved behavioral model for high-voltage and high-power IGBT chips

High-voltage and high-power IGBT chips have a noticeable carrier storage effect, which is related to the load current. However, the research of the carrier storage effect of existing IGBT behavior models is insufficient. In this paper, An improved behavioral model for high-voltage and high-power insulated gate bipolar transistor (IGBT) chips is proposed, which could be used under different load conditions. The problems for applying the traditional behavioral model to more load conditions are discussed. The carrier behavior in the wide base region is analyzed, and the analytical expression of the carrier-storage-effect equivalent capacitance and the initial value of the tail current are given to establish the improved IGBT behavioral model. The corresponding parameter extraction method is proposed. In order to verify the improved behavioral model, an experimental platform is built for resistive load and inductive load, and the results show that the accuracy of the improved behavioral model is much better than that of the traditional model. Besides, the errors of the improved model are within 12.5% under different current and load types. Considering that the maximum error of other models that could be applied in a variety of load conditions is more than 25%, the accuracy of the model proposed in this paper is excellent.

Prediction Method of Driving Strategy of High-Power IGBT Module Based on MEA-BP Neural Network

An insulated gate bipolar transistor (IGBT) driver is crucial for improving the reliability of a power electronics system. This paper proposes a method for predicting the optimal driving strategy of high-power IGBT module based on backpropagation neural network optimized by the mind evolutionary algorithm in order to solve the problem of compromise among switching loss, switching time and overshoot and achieve a good driving effect. The three regions of switching transitions are analyzed based on the switching characteristics of the IGBT module. Neural networks are established to predict turn-on and turn-off driving strategies for variable gate resistance active gate driver of the IGBT module. The mind evolutionary algorithm is used to optimize the weights and biases of the neural networks so that the optimal weights and biases can be obtained. In order to verify the effectiveness of the driving strategy prediction method proposed in this paper, experiments are carried out for 4500V/900A the IGBT module. Compared to the conventional gate driver, the predicted driving strategies reduce the turn-on energy loss, turn-on time, overcurrent, comprehensive evaluation method, turn-on delay time and tail voltage duration by 59.31%, 46.38%, 36.99%, 65.65%, 1.9 μs, 2.9 μs, respectively. It was also found that the Planar-IGBT turn-off process was rarely affected by the gate resistance. The proposed method in this paper can be used not only for the guidance of the driving strategy determination of high-power the IGBT module driver, but also for the driver circuit improvement in the design process.

Thermal mapping at the cell level of chips in power modules through the silicone gel using thermoreflectance

Silicone gel is used in power electronics in order to provide a chemical protection and dielectric insulation in insulated gate bipolar transistor (IGBT) power modules. This gel prevents the direct mapping of surface temperature measurements of the component by classical infrared means. The temperature maps inside IGBT modules are usually performed after removal of the silicone gel which does not allow their operation in real environment. In this paper, we explore the ability of thermoreflectance to overcome this limitation in measuring the temperature surface of an IGBT chip through the silicone gel. Thermoreflectance is a non-contact technique, which measures temperature variation through reflectivity variation measurement. Using a “mean” calibration coefficient determinates from optical fiber thermal measurements, thermal images of IGBT modules with and without silicone gel can be compared. Preliminary results indicate that thermoreflectance enables the measurement of surface temperature change on high power IGBT modules with silicone gel and temperature distribution is affected by the presence of the gel.

A Study on the Effect of Microstructure Evolution of the Aluminum Metallization Layer on Its Electrical Performance During Power Cycling

The study presented in this paper contributes to the quantification of the correlations between resistance degradation and Al metallization layer reconstruction observed in high-power insulated gate bipolar transistor (IGBT) modules during power cycling. The microstructure evolution that occurs in the Al metallization layer during power cycling was investigated via electron and ion microscopy, and the surface roughness was measured and used to characterize Al metallization degradation. An electrical four-point probe method was used to examine the change in the electrical parameter (resistance) of the Al metallization layer in the IGBT modules. The effect of the Al metallization layer reconstruction on its electrical performance was investigated by experimental observation and finite-element analysis (FEA). The results show that both the Al metallization layer surface morphology and cracks propagating across the Al metallization layer thickness significantly affect the metallization resistance. In the initial and mid-point stages of power cycling, the increase in the Al metallization layer resistance is consistent with the surface roughness evolution. Near the ultimate lifetime of the IGBT module, the change in the resistance strongly depends on the crack density.

Insulated-gate bipolar transistor junction temperature estimation based on ℋ∞ robust controller in wind energy applications

This article presents lifetime estimation using robust control based on thermal path degradation condition of insulated-gate bipolar transistor wind power modules. Online measurements of the on-state voltage [Formula: see text] are considered to be a promising method for obtaining a thermal-sensitive electrical parameter for wire-bond lift-off. This parameter demonstrates a good correlation with junction temperature. Due to the harsh environment, disturbances and uncertain parameters are founded within the compact set of wind energy generation systems. The uncertainty sacrifices some degree of accuracy of junction temperature measurements. Hence, robust control theory has been utilized to synthesize [Formula: see text] controller for the thermal impedance of high-power insulated-gate bipolar transistors. To study this reliability problem, an integrated model of wind energy generation system is built in MATLAB/Simulink for the closed-loop system. Simulation results show the benefit of the designed controller compared to the open-loop system in terms of thermal cycles of junction temperature and lifetime estimation.