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48 DESIGN007 MAGAZINE I MARCH 2018 A while ago, I took over the reins of this column from my colleague, Phil Kinner, who covered the subject of conformal coatings in his excellent series of columns. Following my own series of columns on encapsulation resins, Jade Bridges has provided some useful hints and tips on thermal management materials and their role in the protection of vulnerable electronic assemblies. We hope these tutori- als have given readers a better understanding of how high-performance electro-chemicals, when appropriately selected and correctly applied, can prolong the service life of critical electronic systems exposed to environmental extremes and adverse operating conditions. I've been invited once more to be a guest writer for this column and I'm very happy to continue with my specialty subject: resins. For this month's column, I have selected five ques- tions that are frequently asked by our custom- ers. I believe they will help set the scene for an informative sequel to my last series. Extreme environmental conditions are often encountered in the bid to offer protection for PCBs. How do resins offer this protection? Several different factors influence the way resins provide protection. The act of encap- sulating a component or PCB means that it is surrounded by a layer of resin, which, since it is normally done in a single operation, com- pletely seals a component or an entire PCB from the environment in which it operates. A two- part resin, when mixed, starts a chemical reac- tion which results in the resin becoming fully polymerised to provide a homogenous layer. The polymerisation reaction creates a three- dimensional structure which provides a bar- rier against chemical attack and high humidity, for example, and even physical shocks and the destructive effects of thermal cycling. Under less extreme conditions, is a resin still the best option or should a coating be considered as an alternative? What pointers will assist a design engineer to make the choice between these two approaches? This is an interesting point, as the pro- tection provided by a coating offers many advantages over the application of a resin. However, as always, the choice will depend upon what level of protection the PCB designer requires. As a rule of thumb, though, to ensure the highest levels of protection, resins are, overall, superior to coatings. A note of caution here: if weight or vol- ume is a paramount consideration, then a coating is preferred, as this is likely to provide adequate protection while ensur- ing minimal weight/volume increase. On the other hand, if you need to protect your intellectual property and preclude the FAQ: Encapsulation Resins Sensible Design Feature Column by Alistair Little, ELECTROLUBE Q Q A A

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