From small powder to large energy, SiC main drive inverter alleviates electric vehicle "range anxiety"

This is the only choice for many leading manufacturers including ON Semiconductor.

To this end, as early as November 2021, ON Semiconductor announced the acquisition of SiC wafer substrate supplier GTAT, aiming to enhance its own SiC supply capabilities. Earlier in 2019, ON Semiconductor also signed a multi-year SiC wafer supply agreement with CREE.

In addition, with the support of investment and expansion policies, in August 2022, ON Semiconductor's SiC plant in Hudson, New Hampshire, USA was completed. This base will increase ON Semiconductor's SiC wafer production capacity fivefold year-on-year by the end of 2022; in September, ON Semiconductor announced the expansion of its SiC plant in Roznov, Czech Republic. It is expected that in the next two years, this expansion will increase the base's SiC production capacity by 16 times. In September 2023, ON Semiconductor announced the completion of the expansion of its advanced silicon carbide ultra-large manufacturing plant in Bucheon, South Korea, and the wafer plant will be able to produce more than one million 200mm SiC wafers per year.

Thanks to this, in the past two years, ON Semiconductor has achieved 10-fold, 12-fold, 4-fold and 3-fold growth in the four key areas of SiC substrate capacity, bare chip capacity, packaging capacity, and new product launches, respectively.

The booming electric vehicle market is one of the driving forces behind the rapid expansion of SiC production, especially the main drive inverter business of electric vehicles, because higher power density makes the car lighter and faster to charge. According to data provided by Jonathan Liao, product director of the automotive main drive solution department of ON Semiconductor's power solutions division, 40% of the world's new energy vehicles will come from China in 2023, and by 2030, it is expected that there will be 150 million new energy vehicles on the road worldwide, which is undoubtedly an astonishing number.

As a new material, what are the characteristics of SiC compared with traditional silicon materials? From the perspective of physical properties, the electron mobility of SiC is not much different from that of silicon materials, but its bandgap width, breakdown voltage, thermal conductivity and electron migration speed are 3 times, 8 times, 4 times and 2 times that of silicon materials respectively. At the same time, the Mohs hardness of up to 9.5 is also 50% higher than that of silicon materials. This means that power semiconductors based on silicon carbide materials have excellent characteristics such as high withstand voltage, low on-resistance, and small parasitic parameters, which are very suitable for manufacturing many high-power automotive electronic devices, such as on-board chargers (OBCs), buck converters and main drive inverters.

This is indeed the case. Whether on the low-voltage 400V platform or the high-voltage 800V platform, silicon carbide devices can bring significant efficiency improvements to electric vehicles. However, Liao also pointed out that although silicon carbide devices can operate at higher junction temperatures, have faster switching speeds and withstand voltage, these characteristics pose special challenges to chip design, drive optimization, circuit protection, module packaging, and system integration. In addition, the evaluation and certification of long-term reliability of terminal products using silicon carbide materials still have considerable technical difficulties.

"An obvious trend we are seeing is that as automakers pursue higher energy efficiency and endurance, vehicle manufacturers will release more models equipped with 800V platforms in the next two to three years, and the demand for SiC power devices will further increase." Liao said that although the supply chain of 800V platform models, including batteries, inverters, wiring harnesses and other products, is not very mature in the past two years, this situation will soon change in the Chinese market.

When discussing the topic of cross-domain integration of electric drive systems for new energy vehicles, Bret Zahn, vice president of ON Semiconductor's Power Solutions Division and general manager of the Automotive Main Drive Solutions Division, pointed out that cross-domain product integration such as all-in-one is becoming a key technology trend. While electric drive 6-in-1/7-in-1 integrated products are emerging rapidly, the space left for inverters is getting smaller and smaller, but the requirements for output power, integration size, packaging technology and cost have not decreased at all.

He believes that this is precisely the advantage of ON Semiconductor - "We have rich historical experience in SiC vertical integration, there is no doubt about that, from SiC ingot growth, wafers, substrates, epitaxy, to device manufacturing and packaging, the 'one-stop' production model can ultimately ensure that end users are provided with sufficient and reliable product supply, no matter what performance power module they need." Within ON Semiconductor, this is also called "From powder to power", which is the best portrayal of the company's deep cultivation of the vertical integration chain.

ON Semiconductor has unique advantages in bare chip performance, differentiated packaging innovation, and module design, including third-generation planar gate structure silicon carbide devices, exploration of trench gate structures, and continuous iteration of packaging to adapt to different application requirements.

Specifically, ON Semiconductor's silicon carbide power devices currently include three categories: SiC MOSFET, SiC diode, and full SiC and hybrid SiC modules, and are packaged in differentiated die-casting molds. The SiC process platform has evolved from the square cell structure of M1, the hexagonal cell structure of M2 to the strip cell structure of M3, and has performed well in key performance indicators such as on-resistance, switching loss, reverse recovery loss, and short-circuit time, while achieving optimal cost.

In terms of power modules and advanced packaging, by adopting technologies such as silver sintering and double-sided water cooling of die-casting molds, ON Semiconductor has achieved high-efficiency, high-power density power modules (including silicon-based modules and SiC modules) for on-board chargers, main drives, DC-DC converters, etc., to optimize energy use, extend battery life, and ensure stable operation of vehicle electrical systems. The innovative Top Cool MOSFET moves the heat sink pad to the top so that the heat sink can be directly soldered to the device, which not only improves the heat dissipation of the MOSFET, but also allows components to be arranged on the lower side of the PCB, thereby increasing power density and simplifying design.

Take VE-Trac Dual as an example. This is a power module designed by ON Semiconductor specifically for plug-in hybrid electric vehicles (PHEV), full hybrid electric vehicles (HEV), pure battery electric vehicles (BEV) and fuel cell electric vehicles (FCEV). It is optimized for traction inverter applications and implements many innovations, including double-sided cooling, which enables it to have high power density and small size.

The inverter plays a key role in the electric powertrain, equivalent to the fuel injection system in an internal combustion engine, directly affecting the overall energy efficiency of the electric vehicle and the mileage that can be achieved per charge. By developing VE-Trac Dual, ON Semiconductor is expected to achieve higher energy efficiency in a wider range of electric vehicles.

According to the plan, ON Semiconductor's main drive power packaging technology will transition from double-sided indirect water cooling to direct water cooling mode in mid-2023. It is expected to achieve double-sided direct water cooling by the end of 2023, and will be further optimized into a double-sided direct water cooling + solution in mid-2024. The core purpose is to continuously reduce the thermal resistance of the device.

In addition, in order to save time and costs for power electronics engineers to the greatest extent, ON Semiconductor has also launched the Elite Power Simulator online simulation tool and PLECS model self-service generation tool for the EliteSiC series and applications, enabling engineers to obtain valuable reference information by performing system-level simulation of complex power electronics applications in the early stages of the development cycle. It is suitable for soft/hard switching applications, boundary modeling and custom parasitic environments.

"Automotive applications are an important driving force for the SiC market, especially with the popularity of electric and hybrid vehicles. The automotive SiC market is expected to continue to maintain strong growth in 2024." Zahn said that it is unlikely that the SiC market will exceed demand in 2024 , but because the main drive products have high requirements for quality, current output capacity and stable supply, there are not many companies in the market that can make silicon carbide modules, and even fewer that can actually use the products in main drive inverters.

Overall, the development of 200mm SiC wafers will become a trend, which will accelerate the electrification process, promote economies of scale, reduce the cost of SiC devices, and promote their wider adoption in automotive applications. At the same time, in order to ensure supply stability and deal with potential supply chain risks, automakers and SiC suppliers should strengthen cooperation, including signing long-term supply agreements and investing in expansion projects.

In addition, electric vehicles have extremely high requirements for efficient and reliable power management, including main drive inverters, on-board chargers, DC-DC converters, etc. These systems require high-performance power management chips to optimize energy use, extend battery life, and ensure system stability. Electric vehicle motor control requires efficient motor driver chips to achieve precise speed control, torque management, and energy efficiency optimization.

Zahn said that for China, ON Semiconductor will ensure stable and reliable supply by signing long-term supply agreements, and promote innovation and industrial upgrading by building joint technology application laboratories with customers. It is revealed that ON Semiconductor currently has 15 joint laboratories in China. In this way, the two parties can cooperate in the early product design stage of the project, jointly solve technical challenges, and ensure that differentiated products are embedded in the customer's roadmap . At the same time, considering that the ecosystem has experienced supply shortages and supply chain disruptions in the past two or three years, through long-term supply agreements, ON Semiconductor and its customers can form a multi-year supply guarantee, which is a win-win arrangement.

In January this year, ON Semiconductor announced that it had signed a long-term supply agreement with China's Li Auto. Li Auto will use ON Semiconductor's high-performance EliteSiC 1200V bare chips in its next-generation 800V high-voltage pure electric vehicles, and will continue to integrate ON Semiconductor's 8-megapixel high-performance image sensors in its future models. The cooperation with Tier 1 supplier Inovance United Power is also one of the representative cases. For a long time, ON Semiconductor has helped Inovance United Power achieve the best performance by providing high-performance and high-stability IGBT, silicon carbide devices and module combinations.

“In the face of the rapidly changing automotive market, ON Semiconductor and its automaker partners cannot continue to use the traditional automotive industry’s way of thinking and evaluation. They need to adapt to consumers’ changing consumption habits in car purchases and leasing, as well as the rapidly iterating product design cycle, and find a balance between multiple factors such as production yield, size, quality, and price,” Zahn emphasized.

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