Effects of microalloying on the microstructure and properties of high-silicon aluminum alloy for electronic packaging

High-silicon aluminum alloy (Al-50 %Si) for electronic packaging was prepared by rapid solidification and powder metallurgy. Effects of the added elemental copper powder were investigated on the microstructure, mechanical and thermo-physical properties of the alloy. The microstructure and phase composition of the alloy containing different copper contents (0~2 %) were studied by SEM and XRD, and the relationship between copper content and the mechanical and thermo-physical properties was established. The results showed that the size and morphology of Si phase in the microstructure of the alloy changed slightly when the content of copper was less than 1 %. Tensile strength and bending strength increased obviously with the increase of copper content and reached a maximum value of 268.4 MPa and 422.6 MPa, respectively. When the copper content reached 2 %, increased by 44.9 % and 46.7 %, respectively, compared with that without copper. The addition of copper had no obvious effect on coefficient of thermal expansion (CTE) of the alloy. However, the small Al₂Cu phase distributed in the matrix reduced the thermal conductivity by 7.5 %. In summary, with the addition of 1 % copper, the high-silicon aluminum alloy for electronic packaging improved its strength by more than 20 % while maintaining a relatively high thermal conductivity.