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76 DESIGN007 MAGAZINE I SEPTEMBER 2019 of the assembly, which will dictate what can and cannot be achieved. This includes those ar- eas of the circuit that must be coated and those that must not (e.g., connectors, switches, test points, RF shielding, etc.). The best applica- tion method would ensure that each board to be coated receives coating coverage on all re- quired metal surfaces at a sufficient thickness to afford protection against the environment. These requirements will change from board design to board design, and environment to environment; invariably, they need to be test- ed and verified ahead of the production run. Conclusion Implementing a defect-free conformal coat- ing process is a fine balance of material selec- tion, understanding the engineering require- ments for coverage (coat, no-coat, and "don't care" areas), and thickness as well as choosing a suitable application method. Understanding the subtleties of conformal coatings will pay huge dividends in providing an engineering drawing that isn't prone to misinterpretation and making the production team's lives easier. When it comes to designing for conformal coating, there's a great deal more to discuss. Over the following months, I hope to provide more useful tips and design advice that will help you accomplish reliable circuit protection. At Electrolube, we talk solutions every day, so if you have any questions about conformal coating selection, performance, thickness, cov- erage, etc., please do talk to us. DESIGN007 Phil Kinner is the global business and technical director of confor- mal coatings at Electrolube. To read past columns or contact Kinner, click here. Kinner is also the author of The Printed Circuit Assembler's Guide to… Conformal Coatings for Harsh Environments. Visit to download this and other free, educational titles. A phenomenon that is well known from chaos theory was observed in a material for the first time ever, by sci- entists from the University of Groningen, the Netherlands. A team of physicists at the University of Groningen, led by Professor of Functional Nanomaterials Beatriz Nohe- da, made their observation in thin films of barium titanate (BaTiO3), a ferroelastic material. Ferroic materials are characterized by their ordered structure, in shape (ferro- elastic), charge (ferroelectric) or magnetic moment (fer- romagnetic), for example. "These materials are always crystals in which the atoms are arranged with character- istic symmetries," Noheda explains. Electric or magnetic dipoles are aligned within domains in the crystals. However, the dipoles could be pointing up or down, as both states are equivalent. As a result, crys- tals of these materials will have both types of domains. The same goes for ferroelastic materials, best known for their shape memory. In this case, however, the situation is a bit more complicated. Noheda explains, "The unit cells in these crystals are elongated, which means that domains of the different unit cells do not easily match in shape. This creates an elastic strain that reduces the crystal stability." Increasing the temperature increases the disorder (en- tropy) in the material. When the transition starts, domain walls of the new phase appear gradually and both phas- es exist together at intermediate temperatures (30°C to 50°C). Thus, a ferroelectric material at the edge of chaos could give a highly diverse response over a small range of input voltages. The paper in Physi- cal Review Letters is a proof of principle, showing how a material can be designed to exist at the edge of chaos, where it is highly responsive. (Source: University of Groningen) At the Edge of Chaos, Powerful New Electronics Could be Created

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