Effects of Y2O3 contents on microstructure and hardness properties of Sn-Ag-Cu-Y2O3 composite solders

Author(s): EmadM.Ahmed

In this study, varyingof Y2O3particles from 0 to 1 wt.% were incorporated intoSn-1Ag-0.5Cu (SAC-0) plain solder matrix to form composite solders of 0.2 wt.%Y2O3 (SAC-0.2), 0.5wt.%Y2O3(SAC-0.5) and 1wt.%Y2O3 (SAC- 1). Optical (OM) and scanning electron microscopy (SEM) photographs show thatY2O3 particles depressed clearly the growth dendrite â-Sn grains. Since the Y2O3 particles serve as additionalnucleation sites for the formation of primary Sn-rich phase,the size of â-Sn grains were decreasedgradually from 10-15 toµm 2-5 µm range, while the eutectic areas around the â-Sn grainwere shrunkwith higher density of intermetallic particles and Y2O3 particles. XRD results confirmed mainly the presence of â-Sn, Ag3Snphases in all composite solders and the presence of Y2O3 clearly in SAC-1 composite solder. Moreover, lattice parameter of â-Sn was decreased by increasing of Y2O3content in the composite solders referring toenhancement ofCu solubilityin â-Sn for composite solders of higherY2O3content. Thismicrostructure improvement of composite solders leads to microhardness enhancement of SAC-0.2, SAC-0.5 and SAC-1 composite solders with 10.6%, 16.3% and 29% compared to the plain solders SAC-0, respectively.

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