High-fraction Si/Al Electronic Packaging Materials Prepared By Powder Semi-solid Squeeze

As a new type of lightweight electronic packaging material,high-fraction Si/Al alloy not only has the advantages of light weight,high thermal conductivity,low coefficient of thermal expansion and good thermal management requirements for chips;but also have good solderability and machinability,compared with other similar materials such as aluminum silicon carbide,which made them have broad application prospects.In this paper,silicon powder and aluminum powder are used as raw materials to prepare Al-Si alloy by semi-solid vacuum hot squeeze process,and the metallographic structure,bending strength,brinell hardness,thermal conductivity and coefficient of thermal expansion of the composites are characterized and analyzed.In this dissertation,the 20?m Si powder was uniformly mixed with 10?m Al powder were used as original materials,high-Si reinforced Al matrix composites with Si mass ratio 50-70%were prepared by powder semi-solid squeeze at temperature 600-800?and squeeze pressure 2.5-5 MPa.The structure of this composite materials are fine and Si particles evenly distribute in Al particles.With the Si content in the composites increased,the liquid phase content of Al was decreased,the squeeze pressure rise from2.5 MPa to 5 MPa due to the power was flowed slowed and the resistance to deformation was increased.With the Si content ranging from 50%to 70%,their bending strength varies between 248 and 179 MPa;the thermal conductivity varies between 140and 120 W/?m·??;the mean coefficient of thermal expansion from room temperature to 100°C can be regulated between 11.32 and 7.55×10^-6°C^-1.The fracture mode of the high-fraction Si-Al matrix composites is mainly brittle fracture and accompanied by Al matrix ductile fracture.The 5?10 and 20?m Si powder was uniformly mixed with 10?m Al powder were used as original materials.Al-50%Si composites was prepared by powder semi-solid squeeze at temperature 600?and squeeze pressure 2.5-3 MPa.the Si particles distribute uniformly in the Al alloy matrix,the sharp edges and corners of the Si particles was changed obviously.On one hand,the increase of Si particle size made Si phase size increased,on the other hand,the increase of Si particle size decreased bending strength,varies between 294 and 248 MPa;due to the effects of interface thermal resistance,the thermal conductivity increased with the increase of Si particle size,varies between 137 and 140;this composites the mean coefficient of thermal expansion from room temperature to 300°C are 13.17?12.54 and12.02×10^-6/?,respectively.The 20?m Si powder was uniformly mixed with 20?m Al powder were used as original materials.Al-80%Si composites was prepared by powder semi-solid squeeze at temperature 900?and squeeze pressure 5-6 MPa.The Si particles gather together obviously and connect with each other to form complete space network.its bending strength and brinell hardness are 130 MPa and 265 HB,respectively;the mean coefficient of thermal expansion from room temperature to 400°C is6.47×10^-6°C^-1;thermal diffusion coefficient and thermal conductivity are 69.59 mm²/s and 124 W/?m·??,respectively.