The microstructure, tensile, and creep behavior of bulk Sn-3.5Ag solder were studied as a function of cooling rate. Controlled cooling rates were obtained by cooling specimens in different media: water, air, or furnace. The cooling rate significantly affected secondary dendrite arm size and spacing of the tin-rich phase, as well as the morphology of Ag3Sn. Ag3Sn was relatively spherical at the fastest cooling rate and had a needle-like morphology at the slowest cooling rate. Both the yield strength in tension and creep resistance of Sn-3.5Ag solder increased with increasing cooling rate while the strain-to-failure decreased. In this study, the mechanical behavior was correlated with the observed microstructure, creep-stress exponents, and fracture behavior, in order to understand the underlying damage mechanisms.
ASJC Scopus subject areas
- Materials Science(all)