High-temperature shear strength of lead-free Sn–Sb–Ag/Al2O3 composite solder

The lead-free Sn–1.7Sb–1.5Ag solder alloy and the same material reinforced with 5 vol.% of 0.3-μm Al2O3 particles were synthesized using the powder-metallurgy route of blending, compaction, sintering, and extrusion. The mechanical properties of both monolithic and composite solders were studied by shear punch testing (SPT) at temperatures in the range of 25–130 °C. Depending on the test temperature, the shear yield stress (SYS) increased by 4.8–8.8 MPa, and ultimate shear strength (USS) increased by 6.2–8.8 MPa in the composite material. The strength improvement was mostly due to the CTE mismatch between the matrix and the particles, and to a lesser extent to the Orowan strengthening mechanism of the submicro-sized Al2O3 particles in the composite solder. The contribution of each of these mechanisms was used in a modified shear lag model to predict the total composite-strengthening achieved.

Research highlights
► Sn–1.7Sb–1.5Ag–2.3Al2O3 composite solder was synthesized by powder-metallurgy route.
► Shear yield stress and ultimate shear strength increased in the composite material.
► The enhanced strength was due to the CTE mismatch between the matrix and particles.
► Contribution of various strengthening mechanisms was used to predict the strength.