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JANUARY 2019 I DESIGN007 MAGAZINE 73 Polyurethane resins are typically used in marine applications where water penetration resistance is critical, and for applications subject to a high level of physical or flexural stress, such as the potting of accelerometers or sensors embedded in road surfaces. If large temperature swings are expected over a short timeframe or prolonged temperature cycles, then the flexible nature of the resin is advantageous, as there is a low probability of stress cracking occurring. Silicones have the widest possible operating temperature range (-50°C to +220°C), and when cured, are the most flexible of the three resin chemistries. Their adhesion to certain substrates is poor—as is their chemical resistance—particularly with reference to acids, aromatics, and ketones. However, due to their aliphatic backbone, they offer excellent UV and colour stability, particularly for direct exterior applications. While they tend to differ widely in terms of performance characteristics, all resin types have excellent electrical insulation properties across their respective temperature ranges. Conclusion Readers should bear in mind that the foregoing offers only general guidelines. Resin chemistries have advanced considerably in recent years, and there are now resins from leading suppliers—such as Electrolube—that exhibit properties and performance criteria often well beyond the normal boundaries expected for that resin type. DESIGN007 Alistair Little is global business/technical director for resins at Electrolube. To read past columns from Electrolube, click here. To download your copy of Electrolube's micro eBook, The Printed Circuit Assembler's Guide to… Conformal Coatings for Harsh Environments, click here. Design Tool Helps Inspire Flexible Electronics for Smart Everyday Objects Researchers in the Sustainable Electronic Technologies Group at the University of Southampton are working with industrial partner PragmatIC to devise a process design kit (PDK) that will expand the potential for its mass market uses of flexible electronics. PragmatIC created ultra-low cost flexible integrated circuits (FlexICs) thinner than a human hair that can be embedded into everyday objects. The technology enables concepts like smart packaging, which can personalize product information and promotional offers, and interactive toys that can track moving pieces and dynamically change rules during play. The new PDK at Southampton is being tailored to be used with industry-standard tools, making the new technology available to a wider community of designers for future applications. Project lead Professor Mark Zwolinski says, "We have been researching, developing and using electronic design automation (EDA) tools for many years in the School of Electronics and Computer Science (ECS) and this project benefits from over 30 years of expertise that includes student projects and design exercises. We are excited to be working with PragmatIC on this promising technology and look forward to seeing creative uses of its FlexICs in smart everyday objects in homes around the world." The collaborative project, known as a knowledge transfer partnership (KTP) and which is supported by InnovateUK, will make use of design tools that are already used in teaching and research in IC design within ECS. (Source: University of Southampton)