Electronics housings of plastic scarcely protect against electromagnetic interference (EMI) that can be triggered by electromagnetic fields. Since January 1996, the electromagnetic compatibility act (EMVG) has therefore been in force as part of EU harmonization. All electrical and electronic devices and systems must be tested for Electromagnetic compatibility (EMC) before they are used.
The metallization of plastic components by vacuum deposition (PVD) effectively screens noise-sensitive plastic components. This EMC coating by the vapor deposition of aluminum or copper/nickel/chrome on plastic parts in a vacuum yields effective electromagnetic absorption over wide frequency. The economical vapor deposition of Al and Cu/NiCr combines the advantages of plastic with those of an aluminum housing.
Properties of the EMC coating
- Aluminum coating 2.5-5 µm thick
- Cu/NiCr- coating 2-4 µm thick
- Good electromagnetic screening
- Protection from electromagnetic discharge
- Adhesion and long-term stability according to UL 746C
- Easy to recycle
- Relatively economical
Other recommended EMC measures
In addition to the EMC coating, the effectiveness of the shielding depends on the design of the plastic housing, the electrical connection and electronic environment of the device. The required electromagnetic compatibility can be additionally improved by using EMC-compliant circuits, conductive seals and cable glands. A damping of 50-70 dB is generally sufficient for effective screening.
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Note: The suitability of plastic parts for metal coatings always needs to be tested beforehand on a sample.