ON Semiconductor’s VE-TracTM SiC Series Provides High Energy Efficiency, High Power Density and Cost Advantages for Electric Vehicle Main Drive Inverter

ON Semiconductor’s VE-TracTM SiC Series Provides High Energy Efficiency, High Power Density and Cost Advantages for Electric Vehicle Main Drive Inverter

The dual carbon goals are accelerating the development of automobiles towards electrification. Innovation in semiconductor technology is helping automobiles transition from fuel vehicles to electric vehicles. The new generation of semiconductor materials, silicon carbide (SiC), will change the future of electric vehicles due to its unique advantages. For example, the use of SiC in key main drive inverters can meet higher power and lower energy efficiency, longer range, lower loss and lower weight, and can better play its advantages in the trend of migration to 800 V, but it faces many challenges such as cost, packaging and technology maturity. ON Semiconductor provides leading intelligent power solutions and has a deep historical accumulation in the SiC field. It is one of the few suppliers in the world that can provide end-to-end SiC solutions from substrate to module. Its innovative VE TracTM Direct SiC and VE-TracTM B2 SiC solutions use stable and reliable planar SiC technology, combined with sintering technology and die-casting packaging to help designers solve the above challenges. Together with the company's other advanced intelligent power semiconductors, it accelerates the market's adoption of electric vehicles and helps future transportation move towards sustainable development.

Development trend of electric vehicle main drive

Regardless of the configuration of the electric vehicle, whether it is fully battery-powered or a series plug-in or parallel hybrid drivetrain, there are several key factors in vehicle electrification: First, the power is stored in the battery, and then the DC power is converted to AC output through the inverter, which is used to power the motor to convert it into mechanical energy to drive the car. Therefore, the energy efficiency and performance of the main drive inverter are key and will directly affect the performance of the electric vehicle and the mileage that can be achieved per charging cycle.

The main drive of electric vehicles pursues greater power, higher energy efficiency, higher bus voltage, lighter weight and smaller size. More power means greater continuous torque output and better acceleration performance. Higher energy efficiency can make the driving range longer and the loss lower. 400 V batteries are the current mainstream and will soon develop towards 800 V. The 800 V architecture can shorten the charging time, reduce losses and reduce weight, thereby extending the driving range. Whether the motor is on the front axle or the rear axle, the smaller motor size makes the available trunk and passenger space larger. These trends have promoted the transformation of power devices in the main drive of electric vehicles from IGBT to SiC.

SiC is the future of main drive inverters

One of the most important characteristics of SiC is that its bandgap is wider than that of Si, and its electron mobility is three times that of Si, resulting in lower losses. The breakdown voltage of SiC is eight times that of Si. The high breakdown voltage and thinner drift layer make it more suitable for high-voltage architectures such as 800 V. The Mohs hardness of SiC is 9.5, which is only slightly softer than the hardest material diamond and 3.5 harder than Si, making it more suitable for sintering. After the device is sintered, its reliability is improved and its thermal conductivity is enhanced. The thermal conductivity of SiC is four times that of silicon, making it easier to dissipate heat, thereby reducing heat dissipation costs.

At the inverter level or vehicle level, SiC MOSFET can achieve lower overall system-level cost, better performance and quality than IGBT. The key design advantages of SiC MOSFET over IGBT in main drive inverter applications are:

• SiC enables higher power density per unit area, especially at higher voltages (e.g. 1200V breakdown)

• Lower conduction losses at low currents, resulting in higher efficiency at low loads

• Unipolar behavior, can operate at higher temperatures, lower switching losses

VE-TracTM SiC series: sintering process + die-casting SiC technology, specially designed for main drive inverter

ON Semiconductor's SiC products with specific packages for main drive inverters include: VE-TracTM Direct SiC (1.7 mΩ Rdson, 900 V 6-pack) power module, VE-TracTM Direct SiC (2.2 mΩ Rdson, 900 V 6-pack) power module, and VE-TracTM B2 SiC (2.6 mΩ Rdson, 1200 V half-bridge) power module, providing the industry's most highly compatible package pins with IGBT or SiC, reducing the need for structural design changes.

Figure 1: VE TracTM Direct SiC (left) and VE TracTM B2 SiC (right)

To improve power output, heat dissipation is essential. In order to achieve the best heat dissipation effect, ON Semiconductor VE-TracTM Direct SiC uses the latest silver sintering process to directly sinter the SiC bare core on the DBC, which is welded to the Pin Fin baseplate, and there is coolant under the baseplate. In this way, the direct cooling path between the chip junction and the coolant helps to greatly reduce the thermal resistance of indirect cooling , thereby ensuring greater power output. For example, the thermal resistance of VE-TracTM Direct SiC with 1.7 mΩ Rdson reaches 0.10℃/W, which is 20% lower than the thermal resistance of VE-TracTM Direct IGBT.

Figure 2: VE-TracTM Direct SiC key features

The differentiated die-casting packaging technology has higher reliability, higher power density, lower stray inductance, better heat dissipation performance, easier power expansion and greater cost advantages than traditional gel modules. Since SiC can withstand an operating temperature of up to 200°C and a continuous working time of 175°C, the plastic die-casting packaging containing SiC further increases the operating temperature than the die-casting IGBT module, resulting in higher output power.

ON Semiconductor conducted a simulation comparison between VE-TracTM Direct IGBT and VE-TracTM Direct SiC under the same conditions. When they provide the same output power, the junction temperature of VE TracTM Direct SiC is 21% lower than that of VE TracTM Direct IGBT, resulting in lower losses and improved energy efficiency.

Figure 3: Simulation results: SiC has lower losses

Improved energy efficiency equates to longer driving range or lower battery cost. For example, using the same 100 kWh battery, the driving range of the SiC solution is 5% longer than that of Si. If the goal is to save costs, the battery size can be reduced to provide the same driving range. For example, switching from a Si solution with a 140 kWh battery to a SiC solution with a 100 kWh battery reduces the battery cost by 5%, but the driving range remains the same.

At the same 450 V DC bus and 150 °C junction temperature (Tvj) conditions, an 820 A IGBT can provide 590 Arms of current and 213 kW of output power, equivalent to 285 horsepower (HP). A 2.2 mOhm SiC can provide 605 Arms of current and 220 kW of output power, equivalent to 295 HP. A 1.7 mOhm SiC can provide 760 Arms of current and 274 kW of output power, equivalent to 367 HP.

Why choose ON Semiconductor's VE-TracTM SiC?

SiC has been used in MOSFET for more than 10 years, but it has not been widely used by automobile manufacturers in main drive solutions. This is because SiC faces many challenges such as higher cost than silicon-based IGBT, supply and availability, implementation difficulties, technology maturity, and packaging that is not suitable for main drive solutions.

ON Semiconductor's history in the SiC field can be traced back to 2004. In recent years, it has acquired GTAT, an upstream SiC supplier, to achieve vertical integration of the industry chain. It is one of the few end-to-end SiC solution suppliers in the world that provides everything from substrates to modules, including SiC ingot growth, substrates, epitaxy, device manufacturing, best-in-class integrated modules and discrete packaging solutions, ensuring a stable and reliable supply chain and helping to optimize costs. In terms of systems, ON Semiconductor also has strong technical and system knowledge, providing global application support for customers. One of the main advantages of the GTAT process is that its SiC can provide very precise resistivity values, and the resistivity distribution of the entire crystal is very uniform. In addition, ON Semiconductor is promoting 6-inch and 8-inch SiC crystal growth technology, and will also invest in more SiC supply chain links, including wafer fab capacity and packaging lines. At the same time, ON Semiconductor has continuously iterated its SiC technology, which has entered the third generation, and its comprehensive performance is in a leading position in the industry, relying on its years of technological accumulation and the technical supplement brought by the acquisition of Fairchild Semiconductor genes a few years ago.

Figure 4: ON Semiconductor’s SiC leadership

The package pins of VE-TracTM SiC and VE-TracTM IGBT are highly compatible, so the transition from IGBT to SiC reduces the work of structural change design. At the same time, VE-TracTM SiC adopts the crimping design of VE-TracTM IGBT, which has reliable welding and can operate continuously at 175℃. It complies with the automotive standards AECQ101 and AQG324, and the power level can be flexibly expanded.

VE-TracTM B2 SiC integrates all of ON Semiconductor's SiC MOSFET technologies in a half-bridge architecture. The die connection uses sintering technology to improve heat dissipation, energy efficiency, power density and reliability. It can work continuously at 175°C and even short-term at 200°C, which meets the AQG 324 automotive power module standard. The B2 SiC module combines sintering technology for die connection and copper clips, and the die-casting process is used to achieve reliable packaging. Its SiC chipset uses ON Semiconductor's M1 SiC technology to provide high current density, strong short-circuit protection, high blocking voltage and high operating temperature, bringing leading performance in electric vehicle main drive applications.