The aluminum coating is applied in a high vacuum. The 99.99 % pure aluminum is vaporized within a short period of time and is deposited on the plastic surface. The thickness of the coating is approx. 2.5 µm. This makes a shielding effect of 30-40 dB possible in the frequency range of 30 to 1000 MHz. The special aluminum coating is also characterized by good adhesion. To achieve an even better shielding effect, other coating thicknesses are available on request.
Certification in accordance with UL 746C / ALVACOAT®*We have certification in accordance with UL 746C for the following materials in the standard OKW colors:
- Cycolac S157
- Rotec ABS 1001 FR/E
- Rotec ABS 3001
- Terluran GP-22
- Novodur P2H-AT
- Lexan 141R(f2)
- Durethan BKV15H2.0+
- Luran KR2867 CWU
- Romiloy ASA/PC 8170
To download a certificate, see the bottom of this page.
*ALVACOAT® is a registered trademark of OKW Gehäusesysteme GmbH and identifies the process used by OKW to coat plastic parts made of standard materials that are certified in accordance with UL 746C.
RFI/EMI and plastic enclosures
The non-conducting material used for plastic cases, for example ABS and PC, has advantages in voltage and contact protection compared with metal materials. It behaves like an insulator.
For devices that cause electromagnetic interference (see also attachment below) or whose operation is impaired by such interference, plastic cases without special measures offer only moderate protection.
The main reasons for EMC-interference are:
- within low range of frequency < 100 MHz
- within medium range of frequency 30-300 MHz
radiation from cables (cable serves as antenna)
- within high range of frequency > 300 MHz
interference radiation penetrating through material and openings
- The complete electric/electronic equipment, including board layout, should be designed in such a way that RFI/EMI requirements are met. This also includes a reduction in conducted interference and the elimination of cable interference radiation.
- Partial screening of the sensitive components or interference radiators.
- Reduction of interfering radiation entering through openings.
- Increase in the screening effect of the case.
Additional RFI/EMI measurementsAs almost every case is provided with openings and cable connections which reduce the shielding effect, it is important to observe the following recommendations:
- Cable glands
In order to maintain the protection class of the case and to improve the cable radiation, a suitable screw fitting of cables becomes necessary.
- Improvement of contact
As contact for our coated plastic cases we offer gaskets consisting of a foam core with silicone material. The silicone sheath contains copper particles that are silver-plated.
Coating of other materials on request.