Soldering terminology

Activity – The measure of flux cleaning strength. The more active the flux, the more effectively it cleans.

Alloy – A metal consisting of two or more materials. One of these materials must be a metal.

Copper – A reddish metal that is very ductile, thermally and electrically conductive, and corrosion resistant.  Copper is often used in soldering alloys.

Fluxing a seam

Flux – A substance that facilitates soldering, brazing, and welding by chemically cleaning the metals to be joined. Common varieties of flux include water-soluble flux and rosin based flux.

Inorganic – A material not containing carbon, derived from non-living substances such as minerals. Inorganic water-soluble fluxes are primarily used with materials that are difficult to solder.

Joint – The point at which two metals are joined together by hot liquid solder. The solder then cools and solidifies to form the finished joint.

Lead – A heavy gray metal that is very soft and ductile and is a poor conductor of electricity. Lead is often used in soldering alloys, though it presents certain health hazards.

Express Flux for Lead Free Solders

Lead free solder

Lead-free Solder – Solder that contains less than 0.2% lead. The use of lead-free solder is becoming more common due to the health hazards of prolonged lead exposure.

Melting Point – The temperature at which a solid becomes a liquid.  A solders’ melting point is a factor in solder selection.

No-Clean Flux – A type of flux that does not require cleaning after soldering. However, it is less active than other types of flux and should only be used with materials that are “easy” to solder.

Organic – A material containing carbon and derived from living organisms. Organic water-soluble fluxes have high activity.

Oxidation – A materials chemical reaction with oxygen. Oxidation causes rust and tarnish to form on metal surfaces & prevents solder from bonding with the material.

Residue – A substance deposited or left behind. Flux residue must often be removed from components because it can be corrosive.

Rosin-Based Flux – A type of flux made from purified pine sap and available in three activity levels. Rosin-based fluxes have lower activity than water-soluble fluxes.

SAC – A type of lead free solder made from tin, silver, and copper. SAC is often preferred for its low melting point.

SnCu –  A type of lead free solder made from tin and copper. SnCu is a commonly used type of lead free solder.

50/50 Lead-Tin Bar Solder - 1/4 lb

50/50 Bar Solder

Solder –  A metal alloy, with a melting point or melting range below 840°F (450°C), which is melted to join metallic surfaces.

Solder Paste – Powdered solder alloy formed into small spheres and coated with a layer of flux.  Solder paste is available in both dispensable and printable forms.

Soldering – A process in which a filler metal is melted at temperatures below 840°F (450°C) to form a join between two base metals.

Stainless Steel – An alloy steel that is designed to resist corrosion. Stainless steel is difficult to solder.

Tin – A silvery white metal that is very soft and has poor strength. Tin is generally used as a base metal in soldering alloys.

Wetting – The contact between a fluid and a surface. A fluid with good wetting ability will spread out over a greater area.