Solidification Behavior of Lead-Free SnAgCu Alloys

The paper reports about influences of cooling rate, alloy composition and thermal storage on the microstructure of Lead-Free SnAgCu alloys. Three different SnAgCu solders were solidified with rates from 0.35 K/min to 37.4 K/min. The microstructure of these bulk specimens show that size and number of intermetallics depend on solidification conditions. The influence of solder composition was investigated by varying the Ag and Cu content. It will be shown how to prevent the formation of large intermetallics by changing process parameters. In addition this paper will present effects of thermal aging, like Ostwald ripening and the coarsening of the microstructure, on two alloys stored at 125degC, for 0.05 h to 500 h.