Have you ever experienced uncontrolled conformal coating migration? Have you had to strip your recently coated boards because conformal coating wicked into non-desired keep out zones? Wicking is a phenomenon caused by a combination of low surface tension coating, which is usually characterized by low viscosity, coupled with strong capillary forces generated by low standoff gaps possessed by the SMT process. Wicking into connectors; onto grounding hole; or under sensitive components will create defects that will have to be reworked, as it may cause reliability concerns with the finished product, which we will describe in detail. There are ways to either reduce and/or eliminate wicking issues through decisions made during preparation, application, and conformal coating selection.
