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High-rate deposition of thick aluminum coatings on plastic parts for electromagnetic shielding

: Heinß, Jens-Peter; Fietzke, Fred


Surface and coatings technology 385 (2020), Art. 125134
ISSN: 0257-8972
Fraunhofer FEP ()
high deposition rate; aluminum thin films; electron beam evaporation; electromagnetic compatibility shielding; thermal load

A new approach is presented for depositing electromagnetic-shielding layers on plastic components by PVD direct metallization for improved electromagnetic compatibility (EMC). Both the plasma pre-treatment and the coating steps were executed using parameters that allow short processing times. Plastic substrates (PC, ABS, and PLA) were exposed to an intense oxygen/argon plasma from a hollow-cathode arc-discharge source. Cross-cut tests revealed that a plasma pre-treatment time of 1 min was sufficient to achieve excellent adhesion. It was possible to deposit a 5-μm aluminum layer onto these different types of plastics using electron-beam evaporation with an axial-beam gun. High-rate deposition can evidently overcome difficulties caused by overheating these synthetic materials. The coatings were applied at a deposition rate above 100 nm/s. Because of this high rate, electron-beam evaporation provided a considerably lower temperature increase for a given layer thickness in comparison to magnetron sputtering. This difference amounted to more than one order of magnitude. The evaporative coating process was also adapted to additively manufactured parts for the first time. The aluminum layers deposited provided the intended functional properties, in particular the electromagnetic shielding. The attenuation in magnetic near field configuration was determined to 44 dB at 3 GHz.