EMC Shielding on Plastic Components by Electron Beam Evaporation

A new approach for electromagnetic compatibility (EMC) shielding layers on plastic components by PVD direct metallizationis demonstrated. Both, the pretreatment and the coating were executed with parameters which allow processing in short time cycles. The plastic substrates (PC, ABS, PLA) were exposed to an intensive oxygen/argon plasma of a hollow cathode-arc-discharge source. A pretreatment time of one minute is sufficient to achieve accurate adhesion in cross-cuttests. Using the electron beam evaporation with an axial beam gun it was possible to deposit a 5 mm thick aluminum layer onto the different types of plastics. It was presented that high-rate deposition can overcome difficulties with overheating of synthetic materials. The coating was realized with a deposition speed of 100 nm/s. Because of the high rate, the electron beam evaporation offers a remarkablel ower temperature raise for a given layer thickness in comparison to magnetron sputtering. This difference amounts to more than one order of magnitude. The deposited aluminum layers fulfill the aimed functional properties, in particular the electromagnetic shielding effect. The determined magnetic attenuation amounts to 80 dB for gigahertz frequencies. The vacuum coating process was also adapted to additively manufactured parts for the first time.