Over the past few months, I have covered the topic of conformal coatings in as much depth as possible. In this column, I’m going to explore some of the essential factors for designers in coating selection. As we have all experienced, sometimes, things are not always as simple or straightforward as we would like them to be, and in any engineering discipline, there is always the slightest chance that something might go wrong. Thankfully, the key to kicking that possibility is to be as fully prepared as possible. Thus, I’m going to concentrate on helping you avoid coating pitfalls in my five-point guide.
Understanding Coating Values
When choosing a conformal coating, consider critical material parameters like CTE, Young’s modulus, Tg, and gas permeability, as coatings can vary widely in these respects. Designers should also be aware that the values listed in a vendor datasheet are generally measured at ambient conditions for newly cured coatings. It is important for designers to understand how the behaviour of materials will vary with temperature and time, especially ageing at higher temperatures. The coating vendor may have information regarding how materials will vary with temperature and time; however, it is imperative to bear in mind that materials will have to be tested by the OEM to make certain the material is fit for use on their assemblies. Temperature excursions must be factored in. For instance, if thermal shock or thermal cycling is overlooked, it could lead to the coating cracking, which will severely compromise its protective capabilities.
To read this entire column, which appeared in the December 2019 issue of Design007 Magazine, click here.