PHASE SELECTION IN UNIDIRECTIONAL GROWTH OF Sn-Ag_3Sn EUTECTIC ALLOY

摘要

The Sn-Ag_3Sn eutectic alloy is one of the candidates for lead-free solders. The solidified structure of this eutectic system is complex. To understand the coupled zone of this alloy, unidirectional solidification experiments have been carried out. At lower growth velocity, eutectic interface appears. On the other hand, Sn-dendrite appears as a primary phase at higher growth velocity. The distance between the dendrite tip and following eutectic interface (ΔL) are measured with varying the growth velocity (V). ΔL, increases rapidly near the transition velocity from eutectic to Sn-dendrite interface with increasing V. ΔL remains constant at higher growth velocity, which indicates that the temperature difference between Sn-dendrite tip and eutectic interface is almost constant, even though both interface temperatures are function of V.