Baienwei AlSi alloy(Si content from 27%—70%) is a silicon particles reinforced aluminum matrix composites formed by improving Si supersaturation in aluminium matrix. AlSi controlled expansion alloys have the features such as low CTE,low density,high thermal conductivity,high electrical conductivity(excellent EMI/RF shielding performance),high hardness,good thermo-mechanical stability,hermeticity, machinability,platability and compatible with microelectronic assembly technology etc.