Reliable polymer-based cases for the protection of power electronics components

© Fraunhofer IMWS
Calculated fiber orientation and final fabricated demonstrator housing components.
The project "PolyLEktronik" was funded by the European Regional Development Fund (ERDF).

As part of the joint research project "PolyLEktronik", Werkzeugbau & Kunststofftechnik Kruse GmbH from Egeln (WBKT) and the Fraunhofer Institute for Microstructure of Materials and Systems IMWS based in Halle (Saale) have been researching and testing, design and manufacturing methods for reliable, series-production-ready polymer cases for power electronics components. To realistically take into account the diverse physical influences and requirements in the manufacturing process and in component operation, the team focused on the application and linking of various simulation tools and the use of microstructural analysis methods. In addition, novel testing methods were applied, which are to be transferred into a standard.

Many things in everyday life that need to be protected due to their fragile content are enclosed by cases. Camera, loudspeaker and computer cases, for example, are to reduce or prevent contact between the components of the respective devices and external influences such as water, dirt or pressure. This is similar in electrical engineering, especially in power electronics. The latter enables the exchange of energy between different systems by converting electrical voltage, current or frequency, thus also increasing the efficiency of the systems. Depending on where they are used, power electronics components are exposed to high voltages, frequent temperature changes, mechanical shocks, humidity or other influences that can greatly affect the service life of the components. Therefore, power electronics components also require special protective cases. Until now, these have often been made of plastic.

The aim of the joint project “PolyLEktronik" was therefore to conduct detailed research into the influence of manufacturing and workloads on the microstructure of polymer case materials and their associated component properties, and to incorporate the findings into the reliable design and manufacturing of housing cases for automotive and power electronics. Two subprojects concentrated on investigating the design and manufacturing of polymer components for automotive and power electronics and on testing and designing concepts for polymer cases. Simulation models were developed and applied for a realistic description of the injection molding process, the calculation of local process- and material-related component properties, and electrical field analysis. Furthermore, extensive physical measurement and analysis methods provided detailed microstructure evaluation and material characterization.

"Electronic components are becoming ever more compact, with more and more components being integrated into ever smaller spaces. In cars or offshore wind turbines, they are subjected to considerable stresses," says Sandy Klengel, head of the "Evaluation of Electronic System Integration" working group and deputy head of the "Materials and Components for Electronics" business unit, who has been conducting research in this area of technology for many years. "This in turn requires new solutions for the production as well as the design of the cases and the engineering polymers used in the process," adds Dr. Matthias Zscheyge, head of the "Thermoplastic-based fiber composite components" group.

The project also involved characterizing the procedural and mechanical properties of different polymer materials and blend components and further developing a test method for power electronics case materials that can be standardized. Moreover, investigations were carried out as to how moisture influences the microstructure of composite materials and their electrical properties and how various environmental factors affect the interaction of polymeric materials on their adjacent electronic components. The latter was analyzed at microstructural level.

Based on a better understanding of the process-related material properties, the quality and reliability of electronic products can be improved, and manufacturing can be made more cost-efficient and material-specific. The developed design, layout and manufacturing methods were successfully transferred and applied to a demonstrator power electronics component. Also, the standardization of the electrical test method opens up more possibilities for material characterization under basic environmental and application-related conditions.

The project was supported by the state of Saxony-Anhalt as part of the ERDF structural funding.