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KIA COATINGS FOR EMI/RFI SHIELDING Electromagnetic Shielding Silver Inks EMI/RFI stand for Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI). RFI is just EMI over the range of 1kHz-10GHz. Electromagnetic Radiation and Radio Frequency Radiation are all around you. They interfere with sensitive components and circuits. Typical sources are power supplies, fluorescent lights, electric motors, switches, relays, and even IC's. Electromagnetic shielding is done for two primary reasons: (1) to keep electronic device from interfering with others and (2) to keep other devices from interfering with yours. WHY DO PLASTICS NEED TO BE SHIELDED? Modern microelectronics depends on the control of electromagnetic interference. The maximum allowable interference is now set by regulation in most countries. In the USA, the FCC regulates emission standards. In Europe, the emissivity standards came into force in 1982 and have been mandatory for makers of electronic/electrical equipment since January 1, 1996. This is very critical for RFID and other radio devices. Some forms of interference can be controlled by suppression of components and good circuit design. Enclosing the circuitry in a shielded enclosure best controls radiated interference. Metal enclosures generally offer very good shielding. Metals are highly conductive and will absorb or reflect electromagnetic waves. A seamless metal sphere offers the ultimate shielding. Plastics provide the enclosure designer with several advantages over metal. Reductions in weight and cost coupled with increased flexibility and aesthetic appeal have led to increased use of polymers. However, plastics are non-conductive and are transparent to electromagnetic waves. Uncoated plastics offer no protection against EMI. METHODS FOR SHIELDING PLASTIC ENCLOSURES To allow plastic to be used as enclosures for computers, mobile phones, medical equipment and other electronic products, several techniques have been developed to make plastic enclosures conductive. There are three essential routes to making a shielded plastic enclosure; the plastic can be coated with nano silver paste ink. In recent years, the use of nano silver has improved the performance. Enclosing the RF components in a metal can or bonding thin metal plates to the plastic enclosure will in some instances provide a cost effective method for shielding. The in-mold foiling process provides an even lower cost option, but the process is limited to fairly simple geometries. By far, the most common means of shielding an enclosure is to apply a silver conductive ink to the surface of the enclosure. APPLICATION OF CONDUCTIVE PAINTS/COATINGS Various companies have developed a large number of conductive paints/coatings for EMI and RFI shielding applications. Most of the formulations are based on adding either one or a combination of metal flakes of nickel, silver plated copper or pure silver coatings. Silver coatings offer the highest degree of shielding. Although water-based paints are available, solvent-based inks provide superior process ability - especially in high volume applications. Solvent-based inks are available in conventional solvents (MEK, MBK) as well mild solvents such as ethyl alcohol, for use on solvent sensitive substrates and thin wall applications. Nickel loaded paints developed some twenty years ago were widely used in the early eighties, however, their use has declined in recent years as copper and silver pigment technology has developed. With increased usage, the price of silver loaded paints has fallen significantly in recent years. Now most products such as mobile phones, modems, and computer monitors are shielded with silver inks or paste. Typical sheet resistance for silver inks and paste are: Nano Silver Ink Paste, Applied thickness 2-3 microns, Typical sheet resistance OHMS/SQ - under 25 mohm/sq. Silver Ink Jet Ink - applied 680 nm - Typical sheet resistance is under 58 mohm/sq CONTACT US FOR FULL SPECIFICATIONS
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