Intermetallic Formation and Fluidity in Sn-Rich Sn-Cu-Ni Alloys

摘要

This paper investigates the phase equilibria and solidification behavior of Sn-Cu-Ni alloys with compositions in the range of 0 wt.percent to 1.5 wt.percent Cu and 0 wt.percent to 0.3 wt.percent Ni. The isothermal section at 268 deg C in the Sn-rich corner was determined. No evidence for a ternary phase was found, and the section is in good agreement with past experimental studies that report wide solubility ranges for (Cu,Ni)_(6)Sn_(5) and (Ni,Cu)_(3)Sn_(4). The vacuum fluidity test was applied to compositions that are liquid at 268 deg C to map the variation in microstructure and flow behavior with composition in this system. Significant variations in fluidity length were measured among the Sn-Cu-Ni alloys, and the variations correlate with the microstructure that develops during solidification. The generated fluidity map enables the selection of Sn-Cu-Ni solder compositions that exhibit good fluidity behavior during solidification and form near-eutectic microstructures.