Silicon Carbide MOSFET Power Module Research Articles

Autonomous Electric Race Car Inverter Development: Revving up the future with resource efficient drive technology

As the electric drive finds its way progressively into important industry sectors like mobility, transportation, agriculture, production, and supporting services, it becomes increasingly important to have individually optimized technical solutions for the manifold applications. Therefore, a high number of engineers with interdisciplinary competencies will be needed soon to comply with the demand of the worldwide markets. A key component for an often-used variant of the electric drivetrain is the full-bridge inverter, which is subject to a wide spectrum of different requirements. In 2021, the University of Denver (DU), started a cooperation with the University of Applied Sciences Augsburg (UASA) to develop a full-bridge inverter for an autonomous, electrical Formula Student race car, using four permanent magnet synchronous machines as an all-wheel drive. To improve the performance of the race car, the inverter must be lightweight, package optimized, electromagnetic compatibility compliant, safe, and reliable when it distributes a maximum of 80 kW instantaneous power from the battery at a voltage between 420 V and 600 V individually to the four wheels. This article documents the inverter development process using silicon carbide MOSFET power modules, with the goal of using future results in the race car and the knowledge transfer for the education of engineering students. This transatlantic partnership between DU and UASA also serves as a success story for intercontinental collaborative development based on modern communication and decentralized development techniques.

A Highly Integrated Multichip SiC MOSFET Power Module With Optimized Electrical and Thermal Performances

This paper proposes a highly integrated multichip silicon carbide (SiC) MOSFET power module packaging with optimized electrical and thermal performances. The structure of the module is to stack the two power switches up and down with the cooling system and the decoupling circuit integrated inside the module. The structural characteristics of the module realize the co-optimization of the switching performance, thermal management, and electromagnetic interference (EMI) issue of the multichip SiC module, which effectively solve the contradiction in the optimization of the electrical and thermal performance. In addition, by optimizing the process flow and designing a variety of soldering fixtures, the feasibility of the process and the engineering margin is increased. Experiments and simulations show that the proposed SiC power module has good electrical and thermal performance. The loop parasitic inductance is reduced to 2.02 nH and the common-mode (CM) current is eliminated. The drain–source voltage overshoot during the turn-off transient is reduced by 76.5%, and the voltage oscillation is significantly improved due to the integration of the decoupling circuit. At the same time, the integrated liquid-cooling heatsink greatly improves the cooling efficiency of the module on the premise of ensuring the insulation performance of the module.

Condition monitoring indicators for Si and SiC power modules

The reliability of power modules plays a crucial role in developing safer and smarter generations of electric vehicles. Condition monitoring represents a possible solution to predict the possible occurrence of catastrophic failures and avoid unexpected breakdowns. More specifically, power modules for inverter applications are a technology requiring condition monitoring indicators to detect ongoing degradation mechanisms. In this work, both silicon IGBT and silicon carbide MOSFET power modules are thermally stressed through the application of a pulsed direct current until reaching end-of-life limits. As a result, two main failure mechanisms occurring at package level are observed: chip solder degradation and bond-wire damages. In addition, on-state voltage, junction temperature, and thermal resistance are measured during the power cycling as parameters to monitor the device states of health. After the test, the chip solder conditions and bond-wires robustness are checked through scanning acoustic microscope images and optical inspections, respectively. The novelty of this work lies in refining and comparing health indicators for silicon and silicon carbide power modules.

Cu Clip-Bonding Method With Optimized Source Inductance for Current Balancing in Multichip SiC MOSFET Power Module

Cu clip-bonding is a promising packaging method for lower resistance, lower inductance, and higher reliability than wire-bonding. Previous studies only simply replace bond wires with Cu clips on an individual die. However, current sharing and thermal coupling issues among multichip modules are still big challenges in the clip-bonded silicon carbide (SiC) <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> power module. In this article, a novel source inductance optimization method is proposed. Extra modification paths (MPs) on Cu clips are used in this method. A clip-bonded half-bridge multichip SiC power module is designed and fabricated to verify the superiority of the method. In a simple straight layout, the distance between adjacent dies is large enough to avoid heat concentration and junction temperature differences resulting from the thermal coupling effect. The MPs structure on the Cu clip is designed to optimize the power source inductances. Parasitic circuit model and mathematical analysis are derived to demonstrate the features of proposed MPs. Simulations and experiments workbench are conducted to analyze drain current sharing performance. Derivation and simulation show the highest branch's inductance is reduced. Test results show the current imbalance and loss imbalance are relatively mitigated, which proves that the effect of power inductances imbalance is suppressed by the proposed optimization method.

A Quasi-Two-Level Medium-Voltage SiC MOSFET Power Module With Low Loss and Voltage Self-Balance

High-voltage and fast-switching silicon carbide (SiC) power modules are needed to construct high-voltage and high power-density converters. Stacking multiple low-voltage SiC devices to increase the equivalent blocking voltage shows advantages in <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -state resistance, current capacity, and cost over one single high-voltage device. An indirect series-connected SiC MOSFET power module using quasi-two-level hybrid-clamp topology is proposed in this article. The voltages across the devices are automatically balanced with an open-loop modulation strategy to avoid sensors and control algorithm. Moreover, only ceramic capacitors are needed besides the MOSFETs and diodes in the topology. Thanks to this, the topology was highly integrated into a power module using SiC dies, which is equivalent to a general-purpose two-level medium-voltage SiC MOSFET power module. The switching losses of the power module show advantages over other stacking methods and even a single high-voltage switch and it can be evaluated with a two-level half-bridge (HB). To achieve this, the automatic voltage-balancing performance is analyzed in detail and the parasitic output capacitance in the topology is investigated, based on which the design considerations are presented. The simulation results from LTspice confirm the voltage-balancing and a 3600V/20A HB power module is built in the lab and the experimental results verify the design.

Compact Modeling of a 3.3 kV SiC MOSFET Power Module for Detailed Circuit-Level Electrothermal Simulations Including Parasitics

In this paper, an advanced electrothermal simulation strategy is applied to a 3.3 kV silicon carbide MOSFET power module. The approach is based on a full circuital representation of the module, where use is made of the thermal equivalent of the Ohm’s law. The individual transistors are described with subcircuits, while the dynamic power-temperature feedback is accounted for through an equivalent thermal network enriched with controlled sources enabling nonlinear thermal effects. A synchronous step-up DC-DC converter and a single-phase inverter, both incorporating the aforementioned power module, are simulated. Good accuracy was ensured by considering electromagnetic effects due to parasitics, which were experimentally extracted in a preliminary stage. Low CPU times are needed, and no convergence issues are encountered in spite of the high switching frequencies. The impact of some key parameters is effortlessly quantified. The analysis witnesses the efficiency and versatility of the approach, and suggests its adoption for design, analysis, and synthesis of high-frequency power converters in wide-band-gap semiconductor technology.

Silicon Carbide Multi-Chip Power Module for Traction Inverter Applications: Thermal Characterization and Modeling

Semiconductor power modules are the key hardware components of a traction inverter. It drives motor speed and torque, managing the energy exchange from battery to motor and viceversa. The increasing demand for electric and hybrid vehicle requests high performance power modules. Power semiconductor devices based on wide band gap compound, like silicon carbide (SiC), have excellent electrical properties in terms of on-state resistance, stray inductance and performance at high commutation frequency. One of the most promising solution is silicon carbide MOSFET power module in which each switch is made by several different dies placed in parallel. Embedded direct cooling system and novel materials with high conductivity (e.g., active metal brazed substrates) can be considered to enhance thermal performance. A robust method is needed to characterize and to predict power module temperature behavior considering the importance of the thermal performance to improve reliability and to optimize module weight and dimensions. According to several parallel dies inside each switch, classic method based on temperature electric sensitive parameter (TSEP) shall be validated with direct measurement. In this framework, it has been reported the thermal characterization of a power module for a traction inverter based on eight silicon carbide MOSFETs for each switch. Both TSEP and infrared measurements have been employed. Thermal behavior has been numerically reproduced, creating a simplified equivalent network and developing a predictive model by finite element method (FEM).

Performance Comparison of State-of-the-Art 300A/1700V Si IGBT and SiC MOSFET Power Modules

Recently, Mitsubishi Electric began the rollout of second generation silicon carbide (SiC) technology in 1200 V and 1700 V class power modules. These new modules, shown in Figure 1, provide greater efficiency and higher power density than previous SiC generations as well as the latest silicon (Si) technology, which enables new capabilities in energy, transportation, and medical applications.

Digitally Controlled Gate Current Source-Based Active Gate Driver for Silicon Carbide MOSFETs

Silicon carbide (SiC) MOSFETs are viable alternatives for silicon (Si) insulated-gate bipolar transistors (IGBTs). However, direct retrofitting of SiC MOSFETs in Si IGBT-based converters is not feasible due to the presence of a higher amount of parasitic inductance. A large voltage and current overshoot along with oscillation are noticed in such attempts as SiC MOSFETs switch very fast. An active gate driver (AGD) can meet the conflicting requirements of faster switching speed and lower overshoot and ringing. A switched current source-based AGD is designed and extensively tested in a 50-kVA voltage source inverter made with SiC MOSFET power modules. The control methodology is discussed and the experimental results are presented in this article.

10-kV SiC MOSFET Power Module With Reduced Common-Mode Noise and Electric Field

The advancement of silicon carbide (SiC) power devices with voltage ratings exceeding 10 kV is expected to revolutionize medium- and high-voltage systems. However, present power module packages are limiting the performance of these unique switches. The objective of this research is to push the boundaries of high-density, high-speed, 10-kV power module packaging. The proposed package addresses the well-known electromagnetic and thermal challenges, as well as the prominent electrostatic and electromagnetic interference (EMI) issues associated with high-speed, 10-kV devices. The high-speed switching and high voltage rating of these devices causes significant EMI and high electric fields. Existing power module packages are unable to address these challenges, resulting in detrimental EMI and partial discharge that limit the converter operation. This article presents the design and testing of a 10-kV SiC mosfet power module that switches at a record 250 V/ns without compromising the signal and ground integrity due to an integrated screen reduces the common-mode current by ten times. This screen connection simultaneously increases the partial discharge inception voltage by more than 50%. With the integrated cooling system, the power module prototype achieves a power density of 4 W/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .

Comparison of High Voltage SiC MOSFET and Si IGBT Power Module Thermal Performance

Silicon carbide (SiC) devices have been gradually applied in power electronic for the characteristics of high voltage, high power densities, elevated operating temperature and low switching energy loss. In this paper, a SiC MOSFET welding power module is proposed based on high voltage Si IGBT standard module structure to evaluate the thermal performance. The thermal lateral spread model expounds the expansion of the heat flow in the vertical crossing of a thermal conductor, and thermal resistance distributions of packaging materials in Silicon carbide and Silicon power module are studied through the COMSOL Multiphysics finite element software based on the thermal lateral spread model assumption that minute changes in thermal conductivity would produce no alterations in heat spreading angle. The result indicate that SiC MOSFET module gives the larger thermal resistance than the Si IGBT module with the same encapsulation structure but higher power densities for SiC, what’s more, the solder for die attach and direct bonding copper which include upper copper, substrate and lower copper contribute more thermal resistance in SiC MOSFET module. The differences of thermal Performance in SiC and Si modules can be obtained to benefit us in optimizing SiC MOSFET power module structure design and packaging materials selection.

Electrical Performance and Reliability Characterization of a SiC MOSFET Power Module With Embedded Decoupling Capacitors

Integration of decoupling capacitors into silicon carbide (SiC) metal oxide semiconductor field effect transistor ( mosfet ) modules is an advanced solution to mitigate the effect of parasitic inductance induced by module assembly interconnects. In this paper, the switching transient behavior is reported for a 1.2-kV SiC mosfet module with embedded dc-link capacitors. It shows faster switching transition and less overshoot voltage compared to a module using an identical package but without capacitors. Active power cycling and passive temperature cycling are carried out for package reliability characterization and comparisons are made with commercial Si and SiC power modules. Scanning acoustic microscopy images and thermal structure functions are presented to quantify the effects of package degradation. The results demonstrate that the SiC modules with embedded capacitors have similar reliability performance to commercial modules and that the reliability is not adversely affected by the presence of the decoupling capacitors.

Power cycling issues and challenges of SiC-MOSFET power modules in high temperature conditions

Silicon carbide (SiC) MOSFETs power modules are very attractive devices and are already available in the market. Nevertheless, despite technological progress, reliability remains an issue and reliability tests must be conducted to introduce more widely these devices into power systems. Because of trapping/de-trapping phenomena at the SiC/SiO2 interface that lead to the shift of threshold voltage, test protocols based on silicon components cannot be used as is, especially in high temperature conditions. Using high temperature SiC MOSFET power modules, we highlight the main experimental difficulties to perform power cycling tests. These reversible physical mechanisms preclude the use of temperature sensitive parameters (TSEP) for junction temperature measurements, so we set up fiber optic temperature sensors for this purpose. Moreover, these degradation phenomena lead to difficulties in both controlling the test conditions and seeking for reliable aging indicator parameters. Finally, a power cycling test protocol at high temperature conditions is proposed for such devices.

A high temperature silicon carbide mosfet power module with integrated silicon-on-insulator-based gate drive

This paper presents a board-level integrated silicon carbide (SiC) mosfet power module for high temperature and high power density application. Specifically, a silicon-on-insulator (SOI)-based gate driver capable of operating at 200 °C ambient temperature is designed and fabricated. The sourcing and sinking current capability of the gate driver are tested under various ambient temperatures. Also, a 1200 V/100 A SiC mosfet phase-leg power module is developed utilizing high temperature packaging technologies. The static characteristics, switching performance, and short-circuit behavior of the fabricated power module are fully evaluated at different temperatures. Moreover, a buck converter prototype composed of the SOI gate driver and SiC power module is built for high temperature continuous operation. The converter is operated at different switching frequencies up to 100 kHz, with its junction temperature monitored by a thermosensitive electrical parameter and compared with thermal simulation results. The experimental results from the continuous operation demonstrate the high temperature capability of the power module at a junction temperature greater than 225 °C.