Electromagnetic Shielding and EMC Coatings

Electromagnetic shielding is a process used to protect sensitive electronic equipment by reducing electromagnetic interference (EMI). Shielding is particularly important in certain situations because electromagnetic fields can interfere with electronic equipment and even pose health risks in some cases.

EMI coatings are often 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 and are often a quick and inexpensive solution to an EC conformance problem.

It is important when deciding upon a suitable coating to know the attenuation that the product is susceptible to. Silver coatings, when correctly applied, work by reflecting signals whereas nickel coatings will tend to absorb signals. The effectiveness of a conductive coating is dependent upon its electrical impedance and conductivity. Plastics are generally non-conductive and are transparent to electromagnetic waves and therefore are not suitable for EMI shielding purposes.

The shielding performance of different coating materials can easily be compared but various 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 differing degrees of geometric complexity. The level of EMI shielding therefore becomes part-specific.

Types of EMC Coating

The degree of absorption and reflection of signals is dependent upon the coating thickness. In essence, the thinner the coating the less absorbent it will be.

At the lowest level, ESD coatings are generally used on for 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 coatings 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 a very effective coating. With a typical low film thickness of 6-12μm this allows for complex parts to be coated with minimal loss of detail.

The Anochrome range of EMC coatings

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, giving 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 the application engineers at Anochrome to ensure the correct product is specified.

Automatic

Parts can be processed using automatic CNC programed robotic equipment, this may require initial investment in bespoke tooling.

Manual

Parts processed with manual input, generally means reduced capital outlay on bespoke tooling.

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