Why is there so much solder and flux spattering with Lead-Free solder?
Flux spattering is related to the composition of the flux used. Lead-Free solders typically use a very active flux in an effort to improve wetting. These highly aggressive fluxes react to high temperatures like drops of cold water on a hot skillet. The flux in the cored-solder abruptly expands and burst through the solder. This phenomena can also occur with rosin-based fluxes but typically only at high temperatures, and not necessarily with all rosin fluxes (activators and chemical formulations vary between flux manufacturers.) Regardless of the flux you use, as a general rule, the higher the temperature, the more spatter you can expect. Hakko has addressed this problem with the “375” V-groove solder feeder. The “375” cuts a v-shaped groove in the flux-cored solder, preventing the flux from expanding in the solder and bursting.
