Key Research Areas

The overall objective of the project is the development of a modular frequency converter to be integrated into electric motors of circulating pumps with significantly reduced volume and weight, increased efficiency, and the reduction of electromagnetic interference.

The approach to miniaturisation lies in the highly compact embedding and galvanic contacting of 1200 V SiC power semiconductors directly within the circuit board structures. In the project, a new path was taken that makes the production of an embedded module possible with the existing means of PCB production alone. The basic idea is to use "pre-embedded" components (pre-packages) that are manufactured in a separate step. The resulting modules offer significant heat dissipation for each individual embedded semiconductor chip via heat spreading. The isolation from the heat sink is achieved with an IMS substrate, which serves as the build-up base for the PCB stack. In addition, a local DC link and damping resistors can already be implemented in the module.

These power modules have a very low leakage inductance and thus optimal switching and EMC behaviour. The DC link capacitor is connected to the power module with low inductance using planar bus bar structures.

Modules manufactured in this way have been successfully evaluated up to 55 A and 950 V and clearly exceed the application requirements. The switching overvoltage was limited to only 4 % of the nominal voltage due to the embedded and extremely low-inductance structure of the switching cell. Since comparatively conventional bonded power modules are in the range of 20-30 %, this novel approach allows a significantly better utilisation of the SiC semiconductors, since less voltage reserve must be kept available, or a higher DC link voltage can be used.