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Using a unique ferro-magnetic filler in a polyurethane binder, a new EMI absorber can suppress frequency noise in a variety of applications. In RFID devices, for example, the absorber is said to enhance the clarity of the signal by the reader device, allowing a clear signal over a greater distance.
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The AB-5000 series from 3M is designed for EMI attenuation applications requiring electromagnetic-absorbing properties, such as mobile phones, notebooks, digital cameras, LCD/PDP TVs, and printed circuit boards for communications. The absorber suppresses radiated noise from emitting devices designed in the broadband radio frequency range.
As electromagnetic compatibility (EMC) concerns and cost sensitivity have become greater, Jerry Peterson, chemical engineer for 3M’s Electrical Markets Division in Austin, Texas, U.S., says the focus has been on designing EMC solutions that are both effective and cost-effective. The latest series, he claims, accomplishes both.
The absorbers are made with a flexible polyurethane resin loaded with a soft metal-flake filler. They have an acrylic, pressure-sensitive adhesive and are protected by a removable liner. Because of the design, the typical attenuation range of this particular absorber series depends on thickness.
“The…products have a uniform distribution of ferro-magnetic filler in the polyurethane binder. The thicker the absorber material, the more filler is present. The more filler is present, the greater its ability to absorb EMI,” Peterson explains. “The product not only can help suppress frequency noise, but its construction can help suppress auditory noise as well.”
As far as addressing cost, Peterson says both design and manufacturing techniques played a role. “One of the factors in limiting product cost was the use of economical polyurethane as a binder, as opposed to the more common silicone binder,” he notes. “Also significant was the process for creating the appropriate type of metal filler, plus creation of a cost-effective process that manufactures the product with a consistent quality.” Designing such processes, he says, required Six Sigma techniques, as well as proprietary methods.
Appliance engineers should find the absorbers easy to work with, Peterson adds. Using standard techniques, the absorbers can be applied to components or enclosures near the component. “Engineers need not worry about short circuits or grounding because the product is an insulating dielectric,” he says.
The absorbers come in thicknesses of 0.1, 0.2, 0.3, 0.5, and 1.0 mm. They are supplied in roll form, making continuous rotary die-cutting possible.
