Appliance Design - January 2008 - (Page 44)

PLASTICS Shielding Solutions Telecom Terminal Using SABIC Innovative Plastics’ LNP Faradex Specialty Compounds. Consider all the tradeoffs before choosing a barrier option. F by larry adams 44 applianceDESIGN January 2008 abricating electronic device housings out of plastic offers several advantages, including design flexibility and inherent coloring, but polymer has an Achilles heel when it comes to electromagnetic interference (EMI), which passes through even the hardest plastic like ghosts through walls. Unchecked interference can cause a range of problems, from mild annoyance in a consumer electronic device to a life-threatening malfunction in a sensitive piece of medical equipment. The issue has become of greater importance to design engineers due to the growth of electronic devices in general, and of wireless devices in particular. And increasingly tighter European regulations targeting interference make it an issue that cannot be ignored. Those regulations make specific demands regarding both a product’s emissions of EMI and its immunity to EMI. The only way to plug the EMI holes in plastic is with some type of conductive material, which can be either embedded inside the polymer material, or applied after molding to the plastic part. There are different approaches to both concepts, and design engineers need to understand all the tradeoffs involved with each before settling on the optimal solution for their product. The following issues need to be examined: The level of immunity defense needed. The level of needed emissions limitations. Cost targets for materials. Assembly/manufacturing costs and need for secondary operations. Effect on molding of the part and tooling life. Design flexibility for the part, particularly regarding color options. Effect on the recyclability of the part. Environmental considerations involved with any post-molding operations. Essential to pondering the first two points is establishing what mandates must be met and how do they limit ones choices. EMI emissions and a product’s immunity against them are regulated in different ways in different places around the world. Fabrizio Montauti, vice president of engineering for WaveZero, a Sunnyvale, Calif., manufacturer of shielding technology that coats products with metallic films, says that in the U.S. the FCC regulates EMI emissions, but does not require products to be certified against their immunity to these radiated fields. This is not true however in Europe where the EU’s EMC directive has stringent rules against about EMI. In a www.applianceDESIGN.com http://www.appliancedesign.com

Table of Contents Feed for the Digital Edition of Appliance Design - January 2008

Appliance Design - January 2008 Contents Editorial Shipments/Forecasts News Watch Makers of Commercial Refrigeration Equipment Turn to Variable-Speed Motors to Improve Energy Efficiency. New Motor Design and Control Scheme Makes Brushless Motors More Economically Feasible for a Wider Range of Applications. External Gas Molding, a Relatively New Technique, Solves Many of the Challenges Associated with the Injection Molding of Large Plastic Parts. Plastic Housings Offer Many Benefits: EMI Protection Isn't One of Them. But, New Materials and Techniques are Solving that Problem. Choosing the Optimal Strategy for Effective EMI Shielding Depends on Both Mechanical and Electrical Requirements Ethernet-Enabled Microcontroller Makes Networking Schemes Easier and More Cost Effective to Implement The Ever-Changing Array of Microcontroller Memory Options Makes it Imperative to Keep Abreast of What's Available to Determine the Optimal Choice for an Application. A Vast Range of Components and Finished Products will be Exhibited at the Country's Preeminent HVAC/R Show, AHR Expo, which is Scheduled for Jan. 22-24 in New York. Advertiser's Index Association Report: PRBA

Appliance Design - January 2008

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