Study On Tape Casting And Sintering Properties Of Aluminum Nitride Ceramics

AlN ceramics were widely used in large scale integrated circuits?LIC?packaging substrates,electrostatic chucks,transparent ceramics for its high thermal conductivity,excellent insulation and dielectric properties,strong corrosion resistance and similar thermal expansion coefficient compared with silicon substrate.In this experiment,AlN ceramic slurry was prepared by doping sintering additivesand mechanical properties reinforcer Y-PSZ respectively.AlN green bodies with uniform morphology and excellent flexibility were prepared by tape casting in organic system.After shearing,laminating and dispensing the raw ribbon and sintering at high temperature and atmospheric pressure,AlN ceramics with the highest density of more than 98%were obtained.In the preparation process of AlN ceramics,the influence factors of organic tape casting were systematically studied and the properties,microstructures and phase compositions of AlN ceramics with different compositions were analyzed.The main experimental contents are as follows:?1?The dispersing effect of triglyceride with different mass fraction on tape casting slurry was studied.The experimental results showed that the viscosity of AlN slurry was the lowest and the most stable when the content of triglyceride was 6wt%.In addition,solid content of slurry,milling time,ratio of plasticizer to binder?R value?were also important factors affecting the rheological properties of slurry.When the solid content of slurry was 60wt%,milling time was 8h and R value was 0.7,the slurry owed the best rheological properties,showing shear thinning pseudoplastic fluid characteristics,which was conducive to the tape casting process.?2?The sintering densification of AlN ceramics could be facilitated by a certain amount of sintering additive CeO₂.The intergranular phase formed by CeO₂ increases with the increase of CeO₂ doping amount during sintering process,then connected and aggregated into a three-dimensional network structure which could become a channel of applied current.With 14%CeO₂ addition,the theoretical density,thermal conductivity and volume resistivity of AlN ceramics reached a favorable compromise of 96.42%,99W·m^-1·K^-1 and 4.75×10¹⁰?·cm,respectively.After a large amount of CeO₂ was added,not only the intergranular phase of CeAlO₃ but also the phase of CeAl₁₁O₁₈ with smaller Ce content was formed.?3?Y₂O₃ and Y-PSZ?partially stabilized zirconia with yttrium oxide as stabilizer? were doped into AlN as sintering additives and mechanical properties enhancers respectively.ZrN phase appeared in the sintering process and flexural strength of AlN ceramics had been greatly improved by pinning the grain boundaries of AlN with the phase transformation stress of Y-PSZ.After sintering,three-point flexural strength of AlN ceramics with a toughening strength of more than 400 MPa were obtained.