413B - Heavy Duty Flux Remover
413B Heavy Duty Flux Remover is specially formulated to dissolve and remove the most stubborn, encrusted, hard, baked-on fluxes and residues left on parts after soldering. It penetrates quickly to remove non-ionic and ionic contaminants left on the non-component sides of circuit boards. It can also work aggressively on isolated and hard-to-reach areas that require spot cleaning. It is also available in aerosol format.
413B is the best flux cleaner for removing rosin, non-rosin, no-clean fluxes, and both ionic and non-ionic contaminants.
For plastics-safe versions, try 4050A and 4140A flux removers.