A low melting point solder for 22 carat yellow gold

Abstract

The gold-germanium-silicon alloy system has been demonstrated to be capable of furnishing solders melting below 450°C for gold jewellery with a fineness above 21 carats. The application of a thin gold plating to the alloys in foil form confers the requisite flow and spreading characteristics, when melted in a nitrogen atmosphere. Good colour matching can be achieved by a short post-soldering heat treatment, which modifies the alloy microstructure. The mechanical properties of these materials, as determined by shear and peel tests, are suitable for jewellery applications, although silicon and germanium differ considerably from gold with regard to their electrochemical potential, the continuous gold matrix ensures that the alloys maintain a high resistance to the acidic cleaning liquids used in domestic environments.