Research On The Preparation Of Aluminum Silicon Alloys For Electronic Packaging By Friction Stir Processing

Al-Si alloy has been used in the electronic packaging industry with many advantages such as small specific gravity,high strength,low thermal expansion coefficient,high thermal conductivity,easy processing and recycling,etc.The common preparation method is subject to various restrictions such as high cost,complex process and low production efficiency,so it cannot achieve mass production.Friction stir machining(FSP)is a new processing technology,which can realize the refinement and homogenization of the microstructure,eliminate the defects and improve the comprehensive performance of the material.In this project,FSP is applied to the modification of as-cast Al-40 Si to prepare high quality material for electronic packaging.At the same time,the influence of modification and heat treatment on the FSP of aluminum silicon alloy is researched.The results show that friction stir processing can eliminate casting defects and improve the size,distribution and morphology of silicon particles.With the increase of stirring pass,the size of silicon particles gradually decreases,the morphology and distribution of silicon is more rounded and more uniform.After four passes FSP,the hardness of alloy increased by 39%,and the tensile strength increased to 194 MPa,which is 8 times that of the base metal.The thermal expansion coefficient and thermal conductivity of the material have been improved after friction stir processing.Modification can preliminarily refine primary silicon,which will enhance the performance of friction stir processing,but with the increase of stirring pass,this enhancement will gradually decrease.The heat treatment before friction stir processing cannot further improve the performance of the stirring zone,and the heat treatment of the stir zone after friction stir processing can make the silicon particles grow up and reduce the mechanical property.In the process of FSP,the pin of the tool is the most easily to wear.The shape of the pin has great influence on the shape and property of stir zone.