- Keith L.
EMI Shielding Strategies
Updated: Nov 12, 2020
WHY EMI SHIELD?
My favorite example is when you’re listening to the radio and hear the speaker making a clicking noise during an incoming phone call. Now imagine this same interference in medical equipment used in Emergency Rooms across the world, hence why companies and Underwriters Laboratory take this issue seriously.
EMI SHIELD TESTING
EMI Shielding is key for the secure functioning of these innovative board assemblies. The shielding methods vary from capping a chip to adhering mesh inserts on a larger substrate. During the process of choosing an EMI shielding method the most important measurement is attenuation, which occurs through absorption and/or reflection of the impinging waves.
EMI shielding effectiveness is the ratio of perpendicular propagation of Electrical and Magnetic waves measured before and after the shielding attenuation. The methods of testing for shielding effectiveness include Open Field Method, Shielded Box Method, Shielded Room Method and Coaxial Transmission Line Method. Most of these methods can be costly, there are labs all around the USA that specialize in this type of testing to meet ASTM and IEEE standards.
FUNCTIONAL COATING: EMI SHIELDING
Coatings can provide a plastic enclosure the conductive properties of metal without adding weight. Metal Plating is an environmental hazard due to its toxic byproducts and the adhesion strength is low when compared to Thermal Spray solutions. Physical Vapor Deposition (PVD) is too expensive and doesn’t survive shock testing. Thermal Spray is the superior coating solutions.
Thermal Spray is a group of technologies that apply semi-molten materials onto a substrate through atomization processes. These are different ways of spraying pure metals, alloys or ceramics on a plastic, ceramic, glass or metal substrate.
EMI SHIELDING: TWIN WIRE ARC SPRAY
Twin Wire Arc Spray is a thermal spray technology that is most widely used in EMI Shielding. Twin Wire Arc Spray is a process in which metal wires are charged and guided to create an electric arc at the tip of a gun to create semi-molten material that is atomized using compressed air. The substrate stays at or below 200 degrees Fahrenheit throughout the quick deposition process. There is no post-process step necessary, the coating is cured to touch in milliseconds. Zinc and Copper are both effective materials for shielding due to their electrical conductivity and environmental stability.
So before you waste your valuable R&D time and money lab testing, be sure that you are going with a proven EMI Shielding method. You could make it your first and last trip to the EMI testing lab. Reach out for more information email@example.com ….