During soldering, rosin based fluxes form fumes which can lead to asthmatic effects. These effects can be permanent and are the main reason extraction is required when soldering processes are carried out. The fumes also cause eye irritation and sensitise the upper respiratory tract.
There are two main alternative flux types to rosin. These are water soluble types and no-clean rosin-free fluxes. The former materials tend to be of high activity and are used when soldering parts of borderline solderability. Because of the high activity, the flux residues need to be removed after soldering, otherwise they may begin to corrode the workpiece. As their name suggests, water can be used for this task.
The no-clean rosin-free fluxes have been available since the late 1990s and use acidic waxes in place of rosin. The flux residue can be left on the joint and usually is more pale coloured than the rosin counterpart. As with rosin materials, different levels of flux activity are available, dependent on the application.
Despite the fact that there are alternative flux materials to rosin, extraction of flux fume should still be carried out, to avoid unnecessary exposure.