A consortium of leading German companies has developed a new way to alloy solders with Co, Fe and Al using a 'reactive alloying method'. The new technology enables the use of these elements for solders without needing to modify soldering processes. Aluminium in particular is a desirable addition because it could form stronger joints.

Until now it has not been possible to pre-alloy aluminium, for example, because it oxidises too readily. This new technique uses metal organic modified flux in solder pastes to react the metals directly into the solder during solder processing.

Co, Fe and Al were tested with stearate, oxalate and citrate.

It was found that Co and Al influence the supercooling but Fe had no effect. Co reduced the supercooling of the cast by around 10'C and affected the nucleation. Al retarded the solidifcation up to 185'C. Co and Fe were found in the resulting microstructure.

The German-government funded project was undertaken by Bosch, Siemens, Fraunhofer, WC Heraeus, Seho, ContiTemic and Neue Materialin Bayreuth. Results were published earlier in 2010 in the journal Soldering & Surface Mount Technology. 

Further work could expand the study to look at bar and wire applications.