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.

En un estudio sobre los costes de la EMC se ha podido comprobar la siguiente relación

Consideración de la EMC costes
durante el desarrollo1
en un producto listo para la producción en serio100
en un producto en uso1000

De aquí se deriva para la selección de la caja adecuada que un equipo electrónico diseñado con arreglo a las exigencias de compatibilidad electromagnética puede utilizarse en un 90% de los casos sin mano de obra ni costes adicionales en cualquier caja deseada.

Es decir, no tiene que renunciar a las importantes ventajas de las cajas de plástico, como

  • diseño elegante
  • costes claramente inferiores
  • menor peso y mayor variabilidad

.

Información básica sobre la compatibilidad electromagnética (EMC)

Dentro del marco de la armonización de la legislación de los países miembros, la Unión Europa ha elaborado directivas comunitarias de compatibilidad electromagnética, que se recogieron el 9 de noviembre de 1992 en la ley alemana sobre compatibilidad electromagnética de equipos y aparatos (EMVG).

La primera consecuencia es que es necesario comprobar la compatibilidad electromagnética, no sólo de las instalaciones de radiotransmisión, sino también de todos los demás equipos, sistemas e instalaciones eléctricos y electrónicos. El objetivo de esta verificación es otorgar el marcado CE, requisito para poder utilizar equipos eléctricos de cualquier tipo a partir del 1 de enero de 1996.

Si no es posible conseguir la compatibilidad electromagnética mediante la configuración adecuada de los circuitos y/o mediante un blindaje metálico interior, hay que tomar las medidas correspondientes en la caja.

Descargar el catálogo de compatibilidad electromagnética EMC