Silicon carbide for mass production

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For many years, silicon carbide (SiC) has been treated as a “dangerous” rival to silicon – at least in the area of power electronics. However, producing it on an industrial scale is still the major sticking point. The “SiC Module” project is supposed to be paving the way in this direction.

 Generally, problems with the range of electric vehicles are blamed on insufficient battery capacities. However, power electronics, which is just as important, is rarely mentioned in this respect. But from an electronic aspect it is actually at the heart of the regenerative drive concept. Ultimately, this is what gets the available energy on to the road with as few losses as possible. It also controls energy recuperation when the vehicle brakes. Experts assume that every additional percentage point gained in efficiency translates into two percentage points more range. ZF Friedrichshafen expects to increase the range by up to ten percent by using silicon carbide.

In other words, efficiency is one of the most important factors when it comes to power electronics. But, of course, space requirements and weight also play a major role. Silicon fulfills these requirements to a certain extent. However, a better solution would be a wide bandgap semiconductor solution with silicon carbide (SiC).

Silicon carbide brings more power to electric vehicles

Silicon carbide
Microchip only recently released silicon carbide modules (SiC) for production. (Image: Microchip).

But in spite of this, there are very few electric cars on the roads, using silicon carbide technology. Only the Tesla Model 3 is moving in this direction with 24 SiC MOSFET modules from STMicroelectronics. But the “efficient” semiconductor has already achieved its first wins on the race track.

Visitors to last year’s electronica were able to admire the race car from the Venturi Formula E Team at the Rohm booth. In its inverter block, SiC power modules convert direct current from the battery into three-phase alternating current for the electric motor. This is a highly complex process, since the frequency and voltage must be continuously adjusted to suit the driving situation. In March this year, Venturi celebrated its first triumph in Hong Kong with silicon carbide components from Rohm and ZF Friedrichshafen.

silicon carbide
Cree supplies SiC wafers to chip producers, such as Infineon, and recently became the exclusive silicon carbide partner of Volkswagen. (Image: Cree).

Other German car makers are also discovering silicon carbide and Formula E as a new technology testing lab. For example, the BMW iFE.18 achieved its first Formula E win in Diriyah, Saudi Arabia in December last year with silicon carbide technology.

However, it will still take three to four years before we can expect to see the technology used widely on public roads. At the same time, market researchers at Yole Développement predict a volume of about USD 1,4 billion for the silicon carbide semiconductor industry by 2023, with an annual growth rate of 29 percent, most of which will come from the automotive industry. But for mass production to occur, appropriate construction and connection technologies will have to be available by then.

Silicon carbide for mass production

To achieve this, scientists at the Fraunhofer IZM are developing the basic conditions for this in the “SiC Module” project, which is funded by the German Federal Ministry of Education and Research (BMBF). The module is based on a classic PCB design. The semiconductor is not wire-bonded to the package but is directly embedded in the circuit with a galvanic-assisted copper contact. This shortens the wires and optimizes power routing.

Dimensioning and mapping out the power electronic modules was carried out in close collaboration with car manufacturers, component suppliers, and module producers. The project goes further than just developing prototypes. The aim is to pave the way towards serial production of silicon carbide with embedding technology.





Silicon carbide (Image: Fraunhofer IZM)

Embedded silicon carbide on the way to serial production in electric mobility. (Image: Fraunhofer IZM).