Electromagnetic shielding with conductive plastic housings

To shield interfering signals from electronics, plastics must meet high EMC requirements. They are then used as substitute materials for die-cast metal housings.

Wagner AG in Waldstatt manufactures electronic housings from die-cast metal or plastic for the automotive industry. Plastic housings are becoming increasingly important due to their low weight and more efficient processing. However, good EMC shielding must be ensured. With EMC plastic housings Wagner can enter new markets.

The aim of this project was to lay the foundations for the development of an EMC-optimized plastic by measuring and modelling EMC shielding properties and to understand the relationships between plastic properties such as conductivity, component geometry (wall thicknesses, holes, gaps, inserts) and shielding. For this purpose, the plastics were to be modified by adding conductive fillers at the Institute of Polymer Technology FHNW and compared with commercial formulations on homogeneous test specimens.

A correlation between electrical resistance and EMC attenuation (1D and 3D) was clearly demonstrated. The EMC shielding could be measured three-dimensionally depending on material, geometry and frequency. For this purpose, a special 3D measurement setup was developed at the Institute for Automation FHNW and various relationships were modelled. It was found that the application-relevant 3D damping values of metal housings are comparable to housings made of EMC plastics.

Important findings were obtained for the formulation and development of EMC-optimized plastics that can meet the very specific requirements of the automotive industry.