Aging Effects on Microstructure and Tensile Property of Sn3.9Ag0.6Cu Solder Alloy

Abstract

Relationships between microstructural and mechanical aging effects in eutectic PbSn and Pb-free solder alloy Sn3.9Ag0.6Cu are reported and compared. The room temperature aged Sn3.9Ag0.6Cu alloy continually age-softened, this softening correlated with the growth of relatively large tin-rich crystals. The 180°C aged Sn3.9Ag0.6Cu alloy initially age-softened, and the minimum flow strength was reached after one day at 180°C. This softening correlated with the growth of relatively large tin-rich crystals and with the coarsening of Ag3Sn particles. When aged at 180°C beyond one day the Sn3.9Ag0.6Cu alloy age-hardened, the hardening correlated with the dispersion of Ag3Sn particles into tin-rich crystals which previously had not contained intermetallic precipitates.

Anomalously high tensile creep rates from thin cast Sn3.9Ag0.6Cu lead-free solder

“…The tiny precipitates have been previously identified as the Ag 3 Sn and Cu 6 Sn 5 intermetallic phases. [15][16][17][18][19][20] In the bulk sample, the IMC eutectic forms a thick continuous network that isolates individual large-size beta-Sn grains. In the thin cast sample, the beta-Sn grains are small and semiconnected, while the IMC eutectic forms a thin semicontinuous network.…”

Dynamic Mechanical Properties and Microstructural Studies of Lead‐Free Solders in Electronic Packaging

“…Several researchers have focused their attention on the eutectic point of the ternary alloy [45,48,49]. The incorporation of copper also introduces a new intermetallic phase into the solder microstructure: Cu 6 Sn 5 [39,47,49,50]. It is noticed from the difference in microstructure of Sn-Ag and Sn-Ag-Cu solders that Ag 3 Sn intermetallics are more prominent and larger in Sn-Ag-Cu than in Sn-Ag solder.…”

“…The ambient temperature shear strength of joints made from Sn-Ag-Cu solders is suggested [39,40] to be weakened by Sn dendrites within the joint microstructure, especially by the coarse Sn dendrites in solute-poor Sn-Ag-Cu. Anderson [40] suggests that optical microscopy produces better micrographs as compared to scanning electron microscopy (SEM) in terms of revealing β-Sn dendritic structures.…”

Issues on Viscoplastic Characterization of Lead-Free Solder for Drop Test Simulations

“…Cooling rates are usually badly controlled within electronics which greatly affects the microstructure and introduces substantial scatter [2,28]. Subsequent phase coarsening at room and service temperature induces yield strength reduction (according to the Hall-Petch relation) and can lead to both softening and hardening, see [29] for a detailed review of annealing processes in SnAgCu.…”