December 08, 2015
Soft soldering of copper, gold and silver without the use of strong acids has been possible for many years. Now a new family of fluxes allows nickel and steel to join the list. The new, non-acidic fluxes have been developed by the Ionic Liquids team at the University of Leicester, working closely with solder manufacturer Qualitek Europe.
Ionic liquids are, in effect, room temperature salt melts and are highly polar. Due to their polarity and ability to complex ions, they also solubilise compounds and salts which normally would only dissolve in highly corrosive or caustic aqueous solutions.They have found uses in electroplating, electropolishing, electrochemistry, immersion coatings and now as fluxes in both electronics and engineering applications.
The new solder flux eliminates the need for inert or reducing atmospheres, specialised equipment, and special pre-treatment. And the residues can be removed rapidly in warm water. Tests, supported by Scanning Electron Microscopy (SEM) micro-section evaluation of the intermetallic layer, have shown them to work on copper, brass, silver, gold, nickel, cast iron and stainless steel at 160°-400°C, much lower temperatures than possible in the past.