Dewetting is a condition that results when molten solder coats a surface and then recedes, leaving irregularly shaped mound(s) of solder separated by areas that are recovered with a thin film of solder and with the basis metal unexposed.
Non-wetting is a condition in which there is partial adherence of molten solder to a surface it has contacted, and the basis metal remains exposed.
While we usually list in this space the primary process setup areas to check, dewetting and non-wetting typically are board-related due to pad surface contamination.
Other things to look for in the process include:
Paul Lotosky is global director - customer technical support at Cookson Electronics (cooksonelectronics.com) plotosky@cooksonelectronics.com.