High-Power SiC Modules Redefine EV Performance with Large-Chip Design
The electric vehicle (EV) industry continues to push the boundaries of efficiency, reliability, and performance, with advancements in power electronics playing a pivotal role in shaping the next generation of drivetrains. At the heart of this evolution lies the power module—a critical component responsible for converting and managing electrical energy in motor drives. As automakers strive to extend range, reduce charging times, and enhance vehicle dynamics, the spotlight has increasingly turned to silicon carbide (SiC) semiconductor technology. A recent breakthrough in high-power-density SiC module design, led by researchers from the Institute of Electrical Engineering at the Chinese Academy of Sciences, is setting a new benchmark for what’s possible in EV powertrain systems.
The study, published in the Journal of Power Supply, introduces a novel approach to SiC MOSFET power module design that leverages large-chip packaging to achieve superior electrical performance, improved thermal management, and enhanced current-carrying capability. The research team, including Dongrun Li, Puqi Ning, Yuhui Kang, Tao Fan, Guangyin Lei, and Wenhua Shi, has developed a prototype that demonstrates significant advantages over conventional designs, particularly in high-demand automotive applications.
The Shift to Silicon Carbide
For years, the automotive industry relied on silicon-based insulated gate bipolar transistors (IGBTs) and metal-oxide-semiconductor field-effect transistors (MOSFETs) for power conversion in electric drivetrains. While these technologies have served the industry well, they are increasingly being outpaced by the demands of modern EVs. Silicon carbide, a wide-bandgap semiconductor material, offers a compelling alternative due to its superior physical properties.
SiC devices exhibit higher breakdown voltage, lower conduction and switching losses, and better thermal conductivity compared to their silicon counterparts. These characteristics translate directly into more efficient power conversion, reduced heat generation, and smaller, lighter components—key factors in the design of high-performance electric vehicles. As a result, SiC-based power modules are now being adopted by leading automakers and tier-one suppliers in flagship models, from Tesla to Porsche.
Despite these advantages, challenges remain in scaling SiC technology for mass-market applications. One of the primary hurdles is managing thermal and electrical imbalances in multi-chip modules, especially when multiple devices are connected in parallel to meet high current demands. Traditional packaging techniques, such as wire bonding, introduce parasitic inductance and resistance that can degrade performance and reliability. Moreover, variations in device parameters—such as threshold voltage, on-resistance, and transconductance—can lead to uneven current sharing among parallel chips, resulting in localized overheating and premature failure.
A New Approach: Large-Chip Packaging with Multilayer DBC
To address these challenges, the research team has developed a high-power-density SiC MOSFET module using a large-chip packaging strategy combined with multilayer direct bonded copper (DBC) substrates. This innovative design aims to reduce the number of parallel chips required while maintaining or even exceeding the current-carrying capacity of conventional modules.
The core of the new module is built around a 1,200 V, 3.5 mΩ SiC MOSFET chip developed by Qingchun Semiconductor. This large-format chip, designated SG2MA35120B, is capable of conducting up to 350 A at 150°C, making it one of the most powerful single SiC devices currently available. By integrating fewer but larger chips, the design minimizes the complexity associated with parallel operation and reduces the risk of current imbalance.
The multilayer DBC packaging technique plays a crucial role in the module’s performance. Unlike traditional single-layer DBC substrates, which can create uneven current paths and thermal gradients, the stacked DBC structure allows for more uniform current distribution and improved heat dissipation. The bottom and top DBC layers serve as separate current-carrying paths, effectively lowering parasitic inductance and resistance. Finite element analysis estimates the module’s stray inductance at just 8.3 nH, a significant improvement over conventional wire-bonded modules.
This low-inductance design not only enhances switching performance but also reduces electromagnetic interference (EMI), a common issue in high-frequency power electronics. The compact layout also contributes to a higher power density, allowing the module to deliver more power in a smaller footprint—an essential consideration for space-constrained automotive environments.
Experimental Validation and Performance Testing
To validate the module’s performance, the team conducted a series of dual-pulse tests—a standard method for evaluating the dynamic behavior of power semiconductor devices. The test setup included a high-voltage DC source, bus capacitors, a pulse generator, and an inductive load, with measurements taken using high-bandwidth current probes and isolated differential voltage probes.
The results were impressive. Under a 800 V DC bus voltage and an operating temperature of 150°C, the module successfully conducted a peak current of 350 A during the first pulse, with clean switching transitions and minimal oscillation. In contrast, a conventional wire-bonded module using the same chip technology exhibited significant gate signal oscillation at just 650 V, indicating instability and potential reliability concerns at higher voltages.
The researchers emphasized the importance of proper probe placement during testing, noting that improper positioning—such as placing a differential probe directly above a bus capacitor—could introduce measurement artifacts and lead to incorrect conclusions. By carefully optimizing the test setup, they were able to obtain accurate and repeatable data that confirmed the module’s robust performance.
Thermal and Electrical Coupling: A Simulation-Based Analysis
One of the most critical aspects of power module design is the interaction between electrical and thermal behavior. In multi-chip systems, the power dissipated by each device generates heat, which in turn affects the electrical characteristics of the semiconductor. This feedback loop—known as electrothermal coupling—can lead to thermal runaway if not properly managed.
To study this phenomenon, the team conducted a comprehensive simulation analysis comparing two configurations: one using four 3.5 mΩ chips in parallel and another using sixteen 16 mΩ chips. Both setups were modeled using a Foster thermal network, a widely accepted method for simulating transient thermal behavior in power electronics.
The simulations revealed that the large-chip configuration offered superior thermal performance. When temperature feedback was not considered, the maximum temperature difference between parallel chips reached over 20°C in the 16-chip setup, compared to less than 10°C in the 4-chip design. When the positive temperature coefficient of SiC MOSFETs was factored in—meaning that on-resistance increases with temperature, naturally promoting current sharing—the temperature differences were further reduced, but the large-chip module still maintained a clear advantage.
The results suggest that reducing the number of parallel devices not only simplifies the design but also improves thermal uniformity, which is critical for long-term reliability. In real-world driving conditions, where load currents can fluctuate rapidly, a more thermally stable module is less likely to experience hotspots or thermal stress-induced failures.
Implications for Automotive Powertrains
The implications of this research extend beyond the laboratory. The team applied their findings to a real-world automotive power module architecture: the Hybrid PACK Drive (HPD) platform, a popular choice for high-power EV inverters. Current HPD modules typically use eight 16 mΩ SiC chips per phase to achieve a current rating of 680 A at 150°C. By replacing these with four 3.5 mΩ chips and leveraging the multilayer DBC packaging, the researchers project that the same module could support a current rating of up to 1,400 A—more than double the original capacity.
This level of performance could enable automakers to develop more powerful electric motors, increase vehicle efficiency, or reduce the size and weight of the inverter without sacrificing output. For example, a lighter inverter means more room for battery capacity, directly translating into longer driving range. Alternatively, the extra power headroom could be used to support high-performance driving modes or fast-charging capabilities.
Moreover, the simplified chip layout reduces the number of wire bonds and interconnects, which are common failure points in power modules. Fewer connections mean fewer potential sources of mechanical stress, thermal fatigue, and electrical resistance—factors that contribute to long-term degradation.
Addressing Manufacturing Variability
Another key advantage of the large-chip approach is its resilience to manufacturing variability. Even within the same production batch, SiC MOSFETs can exhibit significant differences in key parameters such as threshold voltage and on-resistance. These variations, which can be as high as ±40% for threshold voltage and ±15% for on-resistance, make it difficult to achieve perfect current sharing in parallel configurations.
While the positive temperature coefficient of SiC devices provides some self-balancing effect—where a hotter chip naturally reduces its current draw—the effect is limited, especially during transient events. With fewer chips in parallel, the statistical likelihood of extreme mismatches decreases, and the overall system becomes more predictable and stable.
The researchers also noted that the larger chip size allows for more uniform heat distribution across the die, reducing the risk of localized hotspots that can accelerate aging and failure. This is particularly important in automotive applications, where modules must operate reliably for over a decade under harsh environmental conditions.
The Road Ahead: Scalability and Commercialization
While the prototype module demonstrates clear technical advantages, the path to commercialization involves more than just performance. Cost, manufacturability, and supply chain stability are equally important considerations. SiC wafers are still more expensive than silicon, and the fabrication process is more complex. However, as demand grows and production scales, prices are expected to continue falling.
The use of large chips may initially seem counterintuitive from a yield perspective—larger dies are more susceptible to defects—but advances in epitaxial growth and defect management are improving yields. Moreover, the reduction in assembly complexity and the potential for longer module lifetimes could offset higher upfront costs.
The research team is already working with industry partners to refine the design for mass production. One of the co-authors, Wenhua Shi, is affiliated with Qingchun Semiconductor, the company that developed the 3.5 mΩ chip, suggesting a strong link between academic research and industrial application.
Future work will focus on optimizing the thermal interface materials, improving the mechanical robustness of the package, and integrating advanced monitoring and protection features. The ultimate goal is to create a module that not only performs better but also lasts longer and requires less maintenance.
A Step Toward Sustainable Mobility
The transition to electric mobility is not just about replacing internal combustion engines with batteries and motors. It requires a holistic rethinking of every component in the vehicle, from the powertrain to the control systems. High-efficiency power electronics are a cornerstone of this transformation, and innovations like the large-chip SiC module represent a significant step forward.
By enabling more efficient energy conversion, reducing system losses, and supporting higher power densities, this technology contributes directly to the sustainability goals of the automotive industry. Lower losses mean less heat to dissipate, which reduces the need for bulky cooling systems and further cuts weight and energy consumption.
In addition, improved reliability and longevity mean fewer replacements and less electronic waste over the vehicle’s lifetime. As the world moves toward a circular economy, such considerations will become increasingly important.
Conclusion
The research conducted by Dongrun Li, Puqi Ning, Yuhui Kang, Tao Fan, Guangyin Lei, and Wenhua Shi marks a significant milestone in the development of next-generation power modules for electric vehicles. Their work demonstrates that by rethinking traditional design paradigms—moving from many small chips to fewer large ones—and combining this with advanced packaging techniques, it is possible to achieve dramatic improvements in performance, efficiency, and reliability.
As the automotive industry continues to evolve, the integration of cutting-edge semiconductor technologies like silicon carbide will be essential. This study not only advances the state of the art but also provides a practical roadmap for engineers and manufacturers looking to push the limits of what electric vehicles can achieve.
The future of mobility is electric, and with innovations like this, it’s also more efficient, powerful, and sustainable than ever before.
Dongrun Li, Puqi Ning, Yuhui Kang, Tao Fan, Guangyin Lei, Wenhua Shi, Journal of Power Supply, DOI: 10.13234/j.issn.2095-2805.2024.3.93