Flux

Flux

• Flux is a chemical agent that assists in the soldering process by removing and preventing oxide formation.  
• Flux is a catalyst that does not become part of the final metal composition.  
• Flux improves the wetting action of solder by lowering the surface tension of the solder.
• Each flux has an optimum working temperature where it reacts chemically with oxidized metal surfaces

Flux activation or working temperature is an optimum range of temperatures where it chemically reacts with oxidized metal surfaces.

Flux for electronics applications:

• Must be heated to remove oxides
• Relatively “inert” at room temperatures

Electronics Fluxes

Water Soluble

• Most active type of flux
• Residue is corrosive and conductive
• Requires cleaning equipment and hot water treatment

Rosin Activated

• Very active flux
• Requires saponifier (chemical) and hot water to clean

Rosin Mildly Activated

• Promotes good wetting on oxidized surfaces
• Requires saponifier (chemical) and hot water to clean

No Clean

• Least active type of flux
• Reflow process must occur within 5 minutes of application
• Low solids content leaves little residue
• No cleaning required or possible