Appliance Design - January 2008 - (Page 48)

PLASTICS altered. Generally speaking, impact performance will typically get reduced when fillers are added. Carbon filled thermoplastics have higher stiffness, higher HDT and smaller mold shrinkage. Stainless-steel-fiber filled thermoplastics have similar mold shrinkage, stiffness, HDT as unfilled resin, says Jiang. Metal and metal-coated additives typically provide less mechanical improvement than traditional glass fiber or carbon fiber reinforcement. However, most parts that require shielding do not typically require mechanical strength. If they do, then the plastic compound can be altered to improve strength. When strength is critical to the application, modification of the plastic compound will provide the needed performance, says Rupprecht. The compounds can be “tuned” to different frequency ranges and also incorporate other properties such as fire retardance. For instance, RTP, recently introduced a family of thermoplastic compounds that were specifically created for use on electronic devices that use the Bluetooth wireless communications protocol. The compounds are tuned to allow transmission of Bluetooth frequencies from the device, while blocking other EMI emissions and providing immunity from EMI from other electronics. SABIC Innovative Plastics’ also recently released a new compound to its LNP Faradex line. The company’s approach is to infuse stainless steel fibers into the plastic compounds so that the finished product features inherent EMI and radio frequency interference. The new line of compounds has resulted in equal shielding ability as past products, but with less of a stainlesssteel fiber load, which the company says helps keep costs and part weight down. The proprietary filler technology also increases modulus to enable strong and durable thin-wall parts. The five new LNP Faradex compounds are alloys of polycarbonate and acrylnitrile butadiene styrene (PC/ABS). Metals serve as a key ingredient in the processes offered by WaveZero, including PVD and electroplating. The California company offers functional thin films of metal coatings that shield EMI. The PVD coating process deposits a thin metallic film by the condensation of a vaporized form of the material onto various surfaces. This process permits the creation of conductive coatings, 0.5 microns to 6 microns thick, that do not chip, peel, or flake. WaveZero also offers the Form/Met EMI suppression process, which Montauti says are the optimal choice for new product development and design teams. The shields are created by thermoforming and die cutting a lightweight plastic substrate that conforms to the interior shape of the housing. The substrate is then metallized, creating a form-fitting shield that is dropped into housing. It can also be shaped just to cover the circuit board. Designed as a separate component that fits in perfectly, the barrier eliminates the need for coating the part after molding and also eliminates the need to use conductive fillers in the polymer. The shield is easily removable for recycling of the device after disassembly at the end of its lifecycle. A plated part or a part filled with stainless steel fibers is not. The diversity of these approaches requires design engineers to establish their priorities and understand the tradeoffs with each method, but they must also keep abreast of new techniques and materials that may change the calculation. The range of shielding methods today provides a solution for nearly every application. And, tomorrow, materials and methods will have even more capabilities. Jiang says that future materials will likely include some with high microwave absorption function in a low frequency range. Another future innovation may include a long-conductive fiber reinforcement process that will give better EMI efficiency. Rupprecht adds that, something that is impossible today becomes can become state-of-the-art tomorrow, and that new materials and processes will continue to evolve to meet challenges in cost, performance, and processing. “For example, commercial nano-materials for shielding are not yet available, but it seems that nanotechnology can improve on the aspect-ratio related issues of cost/content and performance.” < For more information, enter: RTP Co . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307 Or email: rtp@rtpcompany .com SABIC Innovative Plastics . . . . . . . . . . . . . . . . . . . . . . 308 Or email: productinquiries@sabic-ip .com WaveZero . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309 Or email: scott .aaron@wavezero .com www.applianceDESIGN.com For more Information Enter 115 48 applianceDESIGN January 2008 http://www.elec-troninc.com http://www.elec-troninc.com http://www.appliancedesign.com

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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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