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Plastics show sustainable promise for heat management in LED applications |
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Light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator lamps in many devices, and are increasingly used for lighting. They also enjoy use in applications as diverse as replacements for traditional light sources in automotive lighting (particularly indicators) and in traffic signals. Their compact size has allowed new text and video displays and sensors to be developed, while their high switching rates are useful in advanced communications technology.
Light Emitting Diodes (LEDs) have recently gained ground compared to the conventional incandescent and fluorescent lighting systems due to obvious benefits. The plus points include low electricity consumption, long extended lifecycles, and environmental impact. However, LED lighting systems, like other systems, face the problem of managing the extreme heat generated. Although LEDs consume little energy, some of their energy is converted into heat, not light, which reduces efficiency. Recent advances provide evidence of the fact that developments in heat dissipative plastics and fillers for plastics are slowly beginning to replace metals like aluminum for heat control purposes in LEDs. As a result, LEDs can benefit from heat dissipative polymers for heat management owing to their low weight, flexibility in design, high efficiency, and low costs. LED system manufacturers are beginning to realize the benefits of high-thermally-conductive plastics and fillers for manufacturing LED enclosures and heat sinks.
Philips, a leading energy efficient lighting solutions provider, recently launched a new LED lamp which marked the first high-power LED application to replace aluminum cover with a thermally conductive plastic for heat control and heat management. The new MASTER LED MR16 retrofit lamp employed DSM�s Stanyl high performance polyamide (PA) for its heat control needs. For this unique product, Philips was on a look out for a material that would deliver superior heat management while at the same time offer greater design flexibility and the same or enhanced product performance. As a result, the two companies zeroed in on the thermally conductive plastic material in order to create lightweight, highly efficient LED lamps that reduce electricity consumption and offer extended lifecycles. According to its makers, thermally conductive Stanyl performs better than aluminum if applied in the right conditions and design. In addition, this polyamide grade also offers the additional benefits of thermoplastics including flexibility in design, exceptional durability and weight reduction. The Philips LED is a 4W LED replacement for the popular low-voltage halogen spot lamp. With light output equivalent to that of 20W Halogen MR16 lamps, it offers the key benefits of up to 80% energy saving and a 40-times longer lifetime. Philips conceded that this high performance polyamide resin offered required thermal conductivity to successfully dissipate the heat generated by LED. This breakthrough offers a sustainable solution as the new plastic material helps create lightweight, highly efficient LED lamps that reduce electricity consumption and offer extended lifecycles.
Aqualuma Underwater Lighting, Australia-based manufacturer of watercraft and underwater lighting systems is another company which has put thermally conductive plastics to good use for managing heat problems of its LED lights. The company recently began offering boat builders, boaters and marinas around the globe, new types of underwater dock, marina and thru-hull trim tab LED lights featuring heat dissipative polymers. The heat conductive polymers were provided by a US firm called Cool Polymers, Inc. The R&D teams from Aqualuma and Cool Polymers collaborated to find the solution with a new grade of CoolPoly� injection moldable thermally conductive plastic. As a result of more than two years of rigorous testing and evaluation, the teams achieved exceptional level of thermal conductivity in this plastic that are 100 times the value of conventional plastics, and when used as a replacement for aluminum, costs less, is lighter, can be easily molded and doesn't corrode under water. Their newest products are manufactured with a leak-proof housing for a long-lasting LED light source. The company needed to find an injection moldable polymer that would help dissipate the heat generated by the lights while being strong enough to withstand the rigours typical of such applications. The new grade of the thermally conductive thermoplastic proved to be an ideal solution for managing the heat output of LEDs by helping transfer and dissipate the heat close to the source. At the enclosure level, when molded into final LED housings, it serves as a heat sink. At the die level, it provides low coefficient of thermal expansion (CTE) and thermally conductive mass to help transfer and dissipate heat close to the source, and at the board level, the thermally conductive plastics provide three-dimensional molded substrates that transfer LED energy similar to ceramic boards and metal backed boards. Several grades of its the thermally conductive plastics are available for use at die level, board level and enclosure level of LED applications. At the die level, CoolPoly D5506 thermally conductive liquid crystal polymer (LCP) is said to be an ideal choice. Also, its CoolPoly D5108 Polyphenylene Sulfide (PPS) grade is said to be perfectly suited for use at board level while CoolPoly E5101 (PPS) is appropriate choice for LED enclosures.
Japan's Teijin Limited is set to launch Raheama, the thermal management material -- a carbon fiber filler that conducts heat better than metals such as silver or copper making it an ideal heat-conductive filler for plastics. Raheama consists of 50-200 micrometer fibers cut from a cylindrical graphite fiber stock measuring about 8 micrometers in diameter. It disperses well in plastic, allowing manufacturers to produce heat-radiation components of almost any shape. It's thermal expansion coefficient is said to be as low as that of ceramics, so compacts created with the material have exceptional dimensional stability. Raheama has two standard specifications: R-A201 offers superior moldability and dispersion as a filler in plastic or rubber and R-A301 provides superior heat radiation. An especially promising application for Teijin�s carbon fiber filler is in the heat sinks, or heat-radiating metallic sheets, of eco-friendly LEDs. Using polycarbonate sheets made with Raheama filler, experiments with LEDs have demonstrated that it can disperse heat on the level of aluminum. It is a promising substitute to eliminate the need for metal while helping to reduce the weight of LEDs. Even though Raheama is yet to be launched, the company is building a pilot 50 tpa plant at the Teijin Technology Innovation Center for its production, with plans to expand to full-scale operations once the material goes commercial. The company has plans to increase its capacity to 500 tpa plus as the market demand for this innovative thermal conductive filler increase.
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