Coatings World - June 2010

components, or troublesome emitters, within a conductive box or other enclosure. The types of enclosures used include small boxes to cover parts of circuit boards, conductive dips for individual components, jacketing or conduits for wires and cabling, and the cases or outer “skins” of devices or appliances.

EMC markets are created by two separate but related objectives: • Keeping external interference out; and • Keeping internal signals in, which could cause interference in other devices.

Practically all electronic devices are subject to EMC regulations and hence must demonstrate, and be built for, a minimal level of electromagnetic leakage as well as a tolerance for EMI that may come from other sources. And as appliances become “smarter” in conjunction with the smart-grid rollouts, they will also become both more sensitive to and more likely to produce EMI.

The materials, products and strategies used for EMC are fairly similar to those used for ESD protection to an extent. Both involve providing a measure of conductivity to the outer surface of sensitive devices or equipment, but they require different levels of conductivity. For ESD protection, charges are carried to ground and/or resistively dissipated, and can accommodate, or even require, low levels of surface conductivity. On the other hand, EMI shielding requires high mobility of the electrons in the material, meaning much higher conductivity.

These conditions have implications for the materials used. For coatings or filled plastics, generally a much larger quantity of conductive material must be used for EMC, raising costs. And some marginally conductive materials used as fillers for ESD materials may be too resistive even in bulk to be used for EMC materials. Higher conductivity requirements also open some new opportunities. Some filler materials can now be used more comfortably within their percolation thresholds, for instance, and metal foils and sheets become reasonable material options.

According to NanoMarkets, there are several trends occurring that are leading to important new opportunities emerging in the EMC industry.

The explosion in the number of wireless phones in recent years has produced billions of new ever-present devices that need to be protected. Well over one billion cell phones are sold every year and it is not just because the phones themselves emit and receive RF signals for communication; the large number of components within the phones also emits EMI and can be sensitive to it.

The shrinking size of electronic devices and the compo-

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nents within them is making EMC more problematic. The smaller size of the components and their closer proximity to one another makes them more sensitive to the EMI from their neighbors within the same device. In addition, the smaller size of the overall device reduces the space available for EMI shielding solutions. Simple off-the-shelf shielding boxes that worked well in the past often cannot do the job today because they simply will not fit.

Lastly, higher radio frequencies are also becoming more common for communications and this produces problems on two levels. For one, the potential victims of these higher frequencies need to be protected by shielding that is capable of dampening such high frequencies. Also, the equipment that sends and receives these frequencies must be able to block the lower frequencies while receiving the intended band.