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AUGUST 2021 I DESIGN007 MAGAZINE 83 a fast cure, hardness, and high stability, par- t i c u l a r l y i n v a r i a b l e temperature environ- ments. These epoxies also adhere well to most substrates, even difficult substrates with a ver y l o w s u r f a c e te n s i o n , such as PTFE, ensuring a watertight encapsula- tion. You may also need to protect electrical or electronic components f r o m e n c o u n t e r i n g chemicals, including acids, alkalis, solvents, and other substances that pose a threat to delicate circuits and components. Chemical resistance is very much the territory of epoxy resins, although some of the stronger polyure- thane products, as well as some silicone-based formulations, will provide a degree of protec- tion. Many epoxy resin products are effective at protecting units that undergo frequent or permanent immersion in solvents. Some are specifically designed to offer high tempera- ture stability and excellent resistance to a wide range of chemicals and oils. Used in fuel level sensors, which are exposed to some of the most hostile conditions, they can be critical to the reliability and functionality required in automotive applications. ermal shock can have a devastating effect on electronic components, shortening their operating lives at best and completely destroy- ing them at worst. e adverse effects of ther- mal stress can be vastly improved by using two- part epoxy resins that have a low coefficient of thermal expansion (CTE), the best solution for those applications that undergo severe tem- perature cycling or which are likely to suffer thermal shock. Low CTE resins mitigate the mismatch in thermal expansion between the resin, substrate, components, and solder joint. Low CTE epoxy resins can provide dimen- sional stability, protecting the integrity of the whole unit during high and low temperature thermal cycles. Lastly, it is worth remembering that, aside from providing all the protections listed, opaque potting and encapsulation resins also conceal what lies beneath. is could provide an effective foil against counterfeiters or those wishing to copy a circuit layout, helping to protect your intellectual property. Over the following months I hope to provide some useful tips and design advice that will help make life a bit easier for those who are responsible for making the decisions on pro- tecting components and circuitry. I hope the foregoing will help you regarding selecting the right resin for its end use environment. Watch for my next column, where I will be exploring resin systems in more detail. DESIGN007 Beth Turner is head of encapsulation resins at Electrolube. To read past columns from Electrolube, click here. Download your free copy of Electrolube's book, The Printed Circuit Assembler's Guide to… Conformal Coatings for Harsh Environments, and watch the micro webinar series "Coatings Uncoated!"

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