This article presents information that helps to clarify the behavior o
f lead-free, low-melting, eutectic Sn-In and Sn-Bi solders. The Sn-Bi
solder forms a well-defined eutectic microstructure at all solidificat
ion rates, while Sn-In solder forms an irregular eutectic that changes
to a fine-grained two-phase mixture at high solidification rates. Bot
h solders wet copper by forming tin-containing intermetallics; however
, Sn-In forms Sn-In-Cu intermetallics with copper and Au-In intermetal
lics with gold. The steady-state creep behavior of Sn-In and Sn-Bi rou
ghly resembles that of Sn-Pb with similar microstructures. Sn-Bi furth
er resembles Sn-Pb in that its eutectic microstructure recrystallizes
within inhomogeneous shear bands. This is not observed in Sn-In. Both
Sn-Bi and Sn-In exhibit pronounced strain softening during shear defor
mation and show early transitions to tertiary creep. Shear stress-stra
in behavior at normal temperatures and moderate strain rates is govern
ed by creep; the ultimate shear stress can be inferred from the steady
-state creep behavior.