Melting behavior and oxidation resistance of Ce-Sn alloy designed for lead-free solder manufacturing

Ce-Sn pre-alloy (master alloy) was designed for new lead-free solder alloy manufacturing. The microstructure characterization revealed the presence of CeSn3 particles in the Sn matrix. The melting behavior in air was investigated by differential thermal analysis coupled with thermogravimetric analysis. When melting was finished, the pre-alloy started to oxidize instantly, because of a high affinity between CeSn3 and Ce itself to oxygen. The oxidation process of Ce-Sn pre- alloy is described in detail. The solidus (231 degrees C) and liquidus (485 degrees C) temperatures of the alloy were determined by differential scanning calorimetry (DSC). By repetitive DSC measurement, it has been verified that this alloy had to be re-melted in an inert gas atmosphere to prevent oxidation. The master alloy is ultimately used to produce new Ce-containing Sn-Ag-Cu solder alloys.