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48 The PCB Magazine • March 2014 are averaged for ease of data review. However, this is still representative of actual test results. Based on the test data available, a suitable ma- terial can be selected to fit individual needs. Data has shown that, among the materials tested, materials that had least insertion losses performed poorly for reliability. The materials selection process should take all aspects of ma- terial performances into account when select- ing a material. With that in mind, material 'D' would be the best performing material in Dk range of 3.57, @ 20GHz, followed closely by ma- terial 'B' with Dk of 4.09 and material 'A' at 4.24 Dk. However if a variation of 0.52in Dk value, @ 20GHz, can be compensated by design, then material 'B' becomes the best overall choice. Similar studies are planned for polyimide, RF and thermally conductive materials. PCB BEHAVIOR OF MATERIALS IN THE MANUFACTURING ENVIRONMENT continues hardeep s. heer is vice president of engineering and cto at Firan technology group. a new breed of ultra thin super-material has the potential to cause a technological revolution. artificial graphene should lead to faster, smaller, and lighter electronic and optical devices of all kinds, including higher performance photovoltaic cells, lasers, or led lighting. For the first time, scientists have been able to produce and analyse artificial graphene from tradi- tional semiconductor materials. such is the scien- tific importance of this breakthrough, in findings published recently in one of the world's leading physics journals, physical review x. a researcher from the university of luxembourg played an im- portant role in this highly in- novative work. graphene (derived from graphite) is a one atom thick honeycomb lattice of carbon atoms. this strong, flexible, conducting, and transparent material has huge scientific and technological potential. Just recently discovered in 2004, there is a major global push to understand its poten- tial uses. artificial graphene has the same honeycomb structure, but in this case, in- stead of carbon atoms, nanometer-thick semicon- ductor crystals are used. changing the size, shape and chemical nature of the nano-crystals makes it possible to tailor the material to each specific task. the university of luxembourg is heavily in- volved in cross-border, multidisciplinary research projects. in this case it partnered with the institute for electronics, microelectronics, and nanotech- nology (iemn) in lille, France, the debye institute for nanomaterials science and the institute for theoretical physics of the university of utrecht, netherlands and the max planck institute for the physics of complex systems in dresden, germany. university of luxembourg researcher dr. eft- erpi Kalesaki, from the physics and materials sci- ence research unit is the first author of the article appearing in the physical review x. dr. Kalesaki said, "these self-assembled semi-conducting nano- crystals with a honeycomb structure are emerging as a new class of systems with great potential." profes- sor ludger wirtz, head of the theoretical solid-state physics group at the univer- sity of luxembourg, added, "artificial graphene opens the door to a wide variety of materials with variable nano-geometry and 'tun- able' properties." Artificial Graphene a New Breed of Ultra-thin Super-material

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