The mechanical properties and microstructures of copper and brass joints soldered with eutectic tin-bismuth solder

Abstract

The mechanical properties and microstructures ofcopper and brass soldered with eutectic tin-bismuth solder have been determined and the joints examined using metallographic techniques. Joints made with copper were stronger than those made with brass. At the copper/solder interface a uniform layer 2μm thick of Cu5.2Sn5 was formed and at the brass/solder interface a uniform layer 2 μm thick of (Cu, Zn)2.9Sn and an irregular layer 2 to 5μm thick of (Cu, Zn)5.7Sn5 were formed. Copper joints fractured etthocopper/solder interface and brass joints fractured in the internmetalic layer. Copper joints soldered with eutectic Sn-Bi were stronger than copper joints soldered with eutectic Sn-Pb and the reverse was true for brass joints. Results are also given for the effect of thermal shock on copper and brass joints soldered with Sn-Bi and Sn-Pb solders, and also for We fatigue and creep behaviour of joints soldered with eutectic Sn-Bi solder.