EMC coating for plastic enclosures

BOPLA is your competent partner when it is necessary to protect electronics against external interference. We provide three processes which offer you the necessary protection:

•    Copper-chrome-nickel vapour deposition
•    Aluminium vapour deposition
•    Lacquering with conductive copper lacquer

With these processes, the surfaces which are not to be – or must not be – coated are covered with tape or masked.
For reasons of time and cost we give preference to lacquering with conductive copper lacquer. However, in your calculations you must take into consideration the disposal and recycling costs specified by the regulations which relate to electronic waste.

Aluminium vapour deposition takes place in high-vacuum plants in accordance with the Elamet® or Nucotec® processes. Aluminium vapour deposition can be recycled without any major expense, and other advantages consist of an even coating thickness and the reproducibility of the coating. We use a coating thickness of at least 2.5 µm as standard. If required, a greater coating thickness is available on request and at any time, depending on the material used for the enclosure.

The mechanical characteristics of the plastic are not altered by the vapour deposition process, so there is no possibility of brittleness or cracking.

Coating masks are now available for most of our standard enclosures, so this screening method can now be offered at very low cost.

We regret that we are unable to accept returns of enclosures which have been coated at customers' specific requests.

EMC screening for aluminium enclosures

Thanks to its electrically-conductive base material, the enclosure provides good basic screening without any additional screening processes.
Screening against higher frequencies can be provided by the use of additional screening methods using electrically conductive connections in enclosure partitions or seal sections.
In the case of anodised enclosure parts, simply break through the insulating anodised coating, for example by milling or using the relevant connecting elements, while ensuring that electrical conductivity is maintained.

In the case of powder-coated enclosure components, surfaces which are not to be – or must not be – coated can be covered with tape or masked before the lacquering process starts.
Coating masks are now available for most of our standard enclosures, so this screening method can be offered at very low cost.

Additional methods of EMC screening

In all cases in which the processes described above do not provide sufficient screening, additional screening performance can be achieved by the use of contacting seals. If necessary, we can recommend, specify and supply these types of special seals on the basis of your requirements and the type of enclosure.

As an additional effective method of screening, it is possible to fit with an internal metallic encapsulation any components, modules or the entire electronics which are affected by interference. Even when such encapsulation is used, the methods described above can be used to increase the screening performance.

In addition to the screening processes named here, enclosures can also be manufactured out of metal-filled plastic. However, the high costs of materials and the uncertain screening performance mean that this process is currently not of interest. To complete the EMC methods, we supply the appropriate plastic or metal glands for cable insertions with connection options for the cable screen to the enclosure ground connection.

A study of the EMC cost factor produced the following results

Taking EMC into consideration Cost factor
during development 1
at series readiness 100
in use 1000

From these figures, it can be deduced that when it comes to selecting an enclosure, in 90% of all cases, electronics which conform to EMC can be incorporated in every required enclosure without any additional work or expense.

This means that there is no need to do without the main advantages of plastic enclosures because screening is being used. These advantages include:

  • attractive desi
  • considerable price advantage
  • much lighter, more variable

The background to electromagnetic compatibility (EMC)

Within the framework of the harmonisation of national regulations, EMC guidelines were drawn up and, on November 9, 1992, incorporated in the Electromagnetic Compatibility Act.

One result of this is the need to test not only radio-operated equipment but also all electrical and electronic devices, equipment and systems in respect of electromagnetic compatibility. The aim of these checks is to issue the CE mark, which is required for the operation of all electrical devices and equipment since January 1, 1996.

If EMC compliance cannot be achieved by a circuit design which conforms to electromagnetic compatibility and/or by means of a metal internal encapsulation, the appropriate measures can be taken on the enclosure side.

Download EMC-Brochure