Typically HASL would have an uneven distribution of tin lead. This uneven surface could pose an issue for SMT parts, especially for BGA and CSP package types. Due to the rough topography associated with the tin lead plating process, it creates high and low spots which could result in a lead not forming proper contact to the defined pad. The issues are not limited to just the bare boards but also the components. Proper care must be taken when handling fine pitch devices as the leads are also subject to being out of specification. Co-planarity issues can arise due to pick and place, transport and so on. Components as well as incoming bare boards should be inspected prior to commencing with the assembly.