On the effects of secondary phase on thermal conductivity of AIN ceramic substrates using a microstructural modeling approach

This paper reports on mathematical and finite element modeling of the effects of secondary phase (Y₂O₃) volume and location on the thermal conductivity of aluminum nitride (AIN) substrates. Finite element analysis results were also compared with experimental results. From finite element analysis, thermal conductivity of AIN(Y₂O₃) substrates with secondary phase located at the grain boundaries was in agreement with Buhr's model. Maxwell's equation was found to give a good estimate of the thermal conductivity of AIN(Y₂O₃) substrates with the secondary phase located at the triple points, with a varying gradient depending on the thermal conductivity of the individual components. With increasing secondary phase volume, thermal conductivity was higher when the secondary phase was located at the triple points as compared with grain boundaries.