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46 The PCB Design Magazine • May 2016 As I sit down to write my fourth column on the subject of conformal coatings, I'm remind- ed—as we in the UK continue to experience al- most sub-arctic weather conditions this Spring, including snow in April—that it is always best policy to be prepared for those unexpected en- vironmental elements. And where electronic circuit board protection is concerned, that means being prepared for all eventualities. So, as the central heating is fired up a notch or two and the barbecue stove is wheeled back into the garage, let's consider what we've covered so far on the subject of conformal coatings. True to form, I'll be providing five PCB de- sign pointers each month to help you avoid some common pitfalls when applying confor- mal coatings. We have so far looked at tricky production related issues that could so easily have been resolved at that all-important design stage, examined some of the more common dos and don'ts; those issues that come up time and time again, despite meticulous attention to design detail, and which must be taken into consideration when coatings are finally applied. We've explored the implications of housing de- sign on conformal coating performance, par- ticularly the influence that fixtures and fittings can have in terms of thermal shock loading and the adverse effects of forced air cooling when abrasive particles are present. So for May, let's cover how the physical shape of board compo- nents and the interaction with solder paste, sol- der masks and fluxes can affect conformal coat- ing integrity. The focus for this month will be my absolute essential facts—my "Never leave home without them" list, so to speak! Fact 1: In an ideal world, PCB designs would not have an inherent weak point for corrosion; unfortunately, in the real world, they do. A re- ally neat way of determining this weak point is to use stress tests such as powered condensation tests. When a weak point is revealed, you are by Phil Kinner ELECTROLUBE CONFORMAL COATINGS DIVISION Coatings: Five Essentials for Designers SENSIBLE DESIGN

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