Electromagnetic shielding protects sensitive equipment by reducing electromagnetic interference (EMI). Shielding is particularly important in certain situations because electromagnetic fields can interfere with electronic equipment, even posing health risks in some cases. The correct electromagnetic shielding is a critical consideration to ensure proper functionality and protection against EMI.
EMI coatings are usually made of conductive materials such as copper, silver, and nickel. Conductive coatings have been successfully used for many years on applications from mobile phones to gas meters. The coatings lend themselves to demanding design requirements. They’re often a quick and inexpensive solution to an EC conformance problem.
It is important when deciding upon a suitable coating to know the weaknesses of the product. The effectiveness of a conductive coating is dependent upon its electrical impedance and conductivity. Silver coatings work by reflecting signals whereas nickel coatings will tend to absorb signals. Plastics are generally non-conductive and are transparent to electromagnetic waves. This makes them unsuitable for electromagnetic shielding purposes.
The shielding performance of different coating materials can easily be compared, however various external factors affect the degree of shielding each coating will give on any particular application. Flat test pieces can be used to give comparative performances between different coating types but they are not representative of fully assembled enclosures with different complexities. This makes the level of EMI shielding part-specific.
There are a wide range of EMC coating options. The level of absorption and reflection of signals is dependent upon the coating thickness. In essence, the thinner the coating the less absorbent it will be. It’s easy to compare different shielding materials on a test trips, although various factors can affect the degree of shielding on a final product. While flat test strips can be used to show comparative performance, these won’t be representative of a fully assembled part with varying geometry.
At the lowest level, ESD coatings are generally used on anti-static enclosures. A 30μm coating is applied and will give a typical surface resistance of 10 to 10 Ω².
Nickel coatings are typically 30-50μm thick and are particularly good at absorbing RF at the lower frequency range.
30μm copper/silver hybrid coatings are commonly used as a general purpose coating. Copper/silver shielding offer improved conductivity, whilst keeping costs at a competitive level.
Silver e-coatings produce very high conductivity and hence high levels of shielding. The high cost of silver can limit the economic size coated, but when applied correctly, silver is very effective. With a typical low film thickness of 6-12μm this allows for complex parts to be coated with minimal loss of detail.
The chart below shows typical attenuation levels against frequency carried out by an Independent test facility, as a comparison between the commonly used paints on an ABS enclosure and Alocrom on an Aluminium enclosure.
The Anotec Ag and Cn series of coatings provides a complete range of Electro Magnetic Compatible EMI shielding for all requirements. They are air drying systems which can be easily applied and are compatible with plastics commonly used for all sizes of electronic enclosures.
The Ag and Cn series of coatings will coat vertical and horizontal surfaces. They give excellent adhesion to substrates such as Polycarbonate, ABS, Polystyrene and ABS/PC blends
Due to the potential differences of coating suitability and application it is always best to speak with one of our the application engineers to ensure the correct product is specified.
Parts can be processed using automatic CNC programmed robotic equipment, this may require initial investment in bespoke tooling.
Parts processed with manual input, generally means reduced capital outlay on bespoke tooling.
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