No Clean (NC)

NC flux consists of rosin, solvent, and a small amount of activator. NC flux typically has low-to-moderate activity and is suited to easily solderable surfaces. IPC classification is usually ROL0 or ROL1. NC residue is clear, hard, non-corrosive, non-conductive, and designed to be left on many types of assemblies. Residue may be removed with an appropriate solvent. Some, but not all, NC fluxes are more difficult to remove than RMA fluxes.

Rosin (R)

R flux consists of rosin and solvent. Rosin flux has very low activity and is suitable only for easy-to-solder surfaces. IPC classification is ROL0. R residue is hard, non-corrosive, non-conductive, and may be left on. Residue may be removed with an appropriate solvent.

Rosin Mildly Activated (RMA)

RMA flux consists of rosin, solvent, and a small amount of activator. Most RMA flux is fairly low in activity and best suited to easily solderable surfaces. IPC classification is usually ROL0, ROL1, ROM0, or ROM1. RMA flux residue is clear and soft. Most are non-corrosive and non-conductive. Many RMA fluxes pass SIR testing as a NC flux. Residue may be removed with an appropriate solvent.

Rosin Activated (RA)

RA flux consists of rosin, solvent, and aggressive activators. RA flux has similar and higher activity than RMA for moderately and highly oxidized surfaces. IPC classification is usually ROM0, ROM1, ROH0, or ROH1. In the absence of testing to prove otherwise, RA flux residue is assumed to be corrosive. Assemblies sensitive to corrosion or the possibility of electrical conduction through the residue should be cleaned as soon as possible after assembly. Residue may be removed with an appropriate solvent.

Water Soluble (WS)

WS flux consists of activators, thixotrope, and solvent. WS flux comes in a wide range of activity levels, from no activity to extremely high activity for soldering to even the most difficult surfaces, such as stainless steel. IPC classification normally starts with OR for organic. They come in L, M, H activity levels and halide content of 0 or 1. By definition, residue may be removed with water.