Choosing the right soldering chemical flux is critical to making a good solder joint. Our selection of water soluble, no clean, rosin and industrial soldering fluxes gives you the best high-quality chemicals to assist in proper solder joint formation.

WHAT IS SOLDERING FLUX ?

Flux is a chemical cleaning agent containing an acid activator and sometimes a wetting agent to prepare surfaces for metal joining.  These are blended or dissolved into a chemical carrier which can be a solvent, water or a thickening agent.  Without flux the molten solder will not "wet" or flow into the surface of the parts being joined or coated.  The right flux allows the solder to partially dissolve into the base metal of the parts creating an intermetallic bond which is where you get mechanical strength.

Flux has three jobs to perform during the soldering process:  First, the flux must clean the metal surfaces by removing contaminants and metal oxides.  Second, the flux must stay in place and keep the surfaces oxide-free until the molten solder is covering the attachment area. Third, it needs to act as a wetting agent, lowering the surface tension between the molten solder and surfaces being soldered so that the solder spreads correctly on the surfaces.

HOW DO I PICK THE RIGHT FLUX TO SOLDER MY PARTS ?

All fluxes contain acids and some of the fluxes need to be removed or cleaned off after you finish soldering.  The best rule of thumb is to select a flux strong enough to clean the oxides on your parts but not attack the parts afterwards.

For soldering electrical or electronic parts you need to use a rosin flux, resin or no-clean flux, or if cleaning afterwards with water an organic acid flux (also known as water-soluble flux).  Rosin soldering fluxes contain natural gum rosin from pine trees and are safe to leave on electrical parts after soldering, thus effectively a no clean flux.  No-clean fluxes are synthetic rosins known as resins; they are similar to natural rosin but engineered to leave less residue and be clear for better cosmetics.  Organic acid fluxes can be used on electronics or some industrial metal parts but need to be completely removed post-soldering with water.  Cored wire solder containing just the right amount of flux is preferable to using a liquid external flux if the soldered area is small enough.

Industrial parts such as copper or brass sheet metal, plumbing parts and other assemblies commonly use organic acid type fluxes.  Metals such as galvanized steel, stainless steel or nickel require highly acidic inorganic acid fluxes in order to penetrate, remove the oxides and bond.  It is important to remove these flux residues after soldering, as even the post-soldering residues will continue to corrode the area surrounding the solder joint after soldering.