Faceting Behavior of Primary Ag in Bi-Ag Alloys for High Temperature Soldering Applications

The solidification behavior and structure of Bi-Ag alloys with low Ag content(0mass% 11mass%) which are now being applied as hightemperature Pb-free solders were investigated. The results show that Bi-Ag alloys exhibited a nonequilibrium eutectic solidification feature andaconsiderablylargeundercooling.AlongercoolingperiodtoreacheutectictemperatureenhancedthefacetingofprimaryAgcrystals.Thelargevalue of the entropy of solution for Ag near the eutectic point should account for this. [doi:10.2320/matertrans.M2009089](Received March 9, 2009; Accepted April 1, 2009; Published June 25, 2009)Keywords: Bismuth-Silver, microstructure, faceting behavior, thermal properties