Effect of minor scandium addition on the microstructure and properties of Al–50Si alloys for electronic packaging

Abstract

Al–50Si alloys for electronic packaging were prepared by gas atomization following hot press sintering, and the influences of adding minor Sc (0.3%) on microstructure and mechanical and thermo-physical properties were studied. The Si phase exhibits a semi-continuous network structure with an average size of 15–20 μm in the alloys with and without Sc addition. Transmission electron microscopy observation indicates that a fine spherical Sc-rich particle distributes at the interface between the Al matrix and Si phase in the Al–50Si-Sc alloy, which is further identified as AlSi2Sc2 (V-phase). The tensile strength, flexural strength, and hardness of the Al–50Si alloy are improved by 16.2%, 8.9%, and 14.7%, respectively, with the introduction of Sc. However, the coefficient of thermal expansion and thermal conductivity decreases slightly in the Al–50Si–Sc alloy as compared with the Al–50Si alloy. The increased strength is mainly attributed to the formation of fine spherical AlSi2Sc2 phase which strengthens the Al matrix.