The Design,Preparation And Performance Analysis Of AlN-Al Composite Coating Used For Micro-electronics Packaging

Some materials used for micro-electrics packaging require high thermal conductivity and low coefficient of thermal expansion,and materials currently used in micro-electrics packaging either have low thermal conductivity or huge coefficient of thermal expansion.Al has high mechanical strength,high thermal conductivity,low density,but high coefficient of thermal expansion;AlN as a ceramic material has good dielectric properties,high thermal conductivity and low coefficient of thermal expansion,but its mechanical strength is insufficient.By optimizing the content of AlN,an AlN-Al composite material with high mechanical strength,high thermal conductivity and adjustable thermal expansion coefficient can be obtained.Plasma spray is mature and cost-effective,and materials used as feedstock are variety.Coatings can be deposited onto substrate with complex structures.Therefore,in this work,vacuum plasma spray(VPS)is used to prepare AlN-Al composite coatings on W-Cu alloy.The optimal AlN content and coating thickness of AlN-Al composite coating is obtained by finite element method(ANSYS Mechanical APDL).Computational micromechanics is used to model the coating and study the effects of AlN content and coating thickness on the effective thermal conductivity(K_eff)and the distribution of residual stress of AlN-Al composite coating.The K_eff and microstructure of as-sprayed coating are characterized by experiments.The as-sprayed AlN-Al composite coating contains many in situ pores and vertical cracks.The effects of pores and cracks on the K_effand residual stress of the as-sprayed AlN-Al coating are studied.Results show that the K_effof as-sprayed AlN-Al composite coating declines as the increase of AlN content,the finite element results are similar to experimental results.Thickness has a little effect on the K_eff,but the increase of thickness will result in the decline of the bond strength of AlN-Al coating and the substrate.The object-oriented finite element results show that vertical crack also has minor effect on the K_eff,but instead contributes to the increase of bond strength.Horizontal crack leads to a great decrease in K_eff.The high level stresses are concentrate around the pores which is the driving force of the initiation of cracks.