Thermal conductivity and dielectric constant of spark plasma sintered aluminum nitride

Aluminum nitride (AlN) possesses excellent properties for use as a substrate or packaging material in the flourishing microelectronics industry. However, AlN is exceptionally difficult to sinter through conventional sintering processes, and pure AlN does not attain full density even at sintering temperatures above 1800 8°C. In this study, pure AlN and calcium fluoride (CaF₂)- doped AlN powders are sintered using the spark plasma sintering (SPS) method. In SPS, densification is enhanced by the application of electrical discharges combined with electrical resistance heating and concomitant uniaxial pressure (45 MPa). The microstructure, thermal conductivity and dielectric constant of SPS AlN samples are examined. Results show that SPS can fabricate samples with superior thermal properties. Addition of 1 wt.% CaF₂ was found to have expedited the sintering process and this yielded thermal conductivity of ∼ 110 W m^-1 K^-1, with relative density of ∼ 95%. Addition of 3 wt.% CaF₂ to the AlN powders demonstrated incremental improvement in thermal conductivity and relative density values at 1700 °C.