Fraunhofer IZM / Electromobility Embedding SiC MOSFETs into a Ceramic Substrate

Embedded silicon carbide on its way to mass manufacturing for e-mobility applications.
Embedded silicon carbide on its way to mass manufacturing for e-mobility applications.

Silicon carbide, a novel power semiconductor material, has been investigated for years. However, the right packaging and interconnection technology for mass production is still missing. The path pursued by the Fraunhofer Institute IZM is the embedding of SiC-MOSFETs in ceramic substrates.

Electromobility has its downsides, with some sceptics pointing to limitations such as top speed and maximum range. Both depend on the built-in power electronics, the electronic heart of e-mobility. Size, weight and efficiency are three critical factors for power electronics to be incorporated into electric cars. Silicon carbide (SiC), a wide-bandgap semiconductor material, complies with all three requirements. It is more efficient and smaller as traditional semiconductors based on silicon.

However, silicon carbide is still mostly in R&D laboratories. In order to transfer it from lab to fab, the SiC module project of the Fraunhofer Institute IZM has taken into account all requirements of industrial manufacturing from its very beginning. The design of the module is an example of this: The researchers have been orienting themselves towards the structure of the classic printed circuit board, which has long been preferred by industrial companies. This should accelerate time to market.

Shorter power lines, better power routing

The module is also benefitting from the latest scientific advances. Rather than wire-bonding the semiconductor to the package, the researchers decided to embed it directly in the circuit with a galvanic-assisted copper contact to shorten the wires and optimize power routing.

As part of this development work, the team also brought the potential customer on board. In the project’s first year, they drew up a specification sheet pinpointing the electrical, thermal and performance requirements for the module and semiconductor. The researchers worked closely with users, incorporating their ideas when they determined the product specs. Carmakers, component suppliers and OEMs were directly involved in the effort to map out the power-electronic modules’ size, layout and electrical circuits. This collective sought to make the most of the space available in the vehicles’ powertrain.

Lars Böttcher, group leader at the Fraunhofer IZM and head of the SiC sub-project project, said: »We’re going beyond a general proof of concept because we are developing more than just a prototype in this project«. The goal is to ramp up both the new semiconductor material silicon carbide and the embedding technology for mass production.

The Federal Ministry of Education and Research is funding the project with 3.89 million euros as part of the E-Mobility Call. Slated to run from January 2018 to December 2020, the project involves six partners alongside the Fraunhofer IZM: AixControl, Conti Temic microelectronic, Rheinisch-Westfälischen Technischen Hochschule Aachen, Robert Bosch, Schweizer Electronic, and TLK-Thermo.