Thermal conductivity of low-temperature sintered calcium aluminosilicate glass–silicon nitride whisker composites

Abstract

A new type of low temperature co-fired ceramic (LTCC) composite, comprising β-Si3N4 whiskers and calcium aluminosilicate (CAS) glass, is introduced in this paper. We show that the CAS–Si3N4 composite can be densified at 775–850 °C in air. The effect of β-Si3N4 whiskers incorporation on the thermal conductivity of this relatively low-temperature sintered CAS–Si3N4 composite is investigated. The thermal conductivity of the CAS glass is increased from 1.6 to 7.9 W/mK after adding 35 vol% of β-Si3N4 whiskers. Microstructure characterization and percolation model analysis indicate that the likely cause of increased thermal conductivity of the ceramic composites is the formation of thermal percolation networks. The crystallization of the CAS glass also contributes to the enhancement of thermal conductivity. The sample with the highest thermal conductivity shows a low relative dielectric constant of 7.1 and a dielectric loss of 0.006 at 1 MHz. Such a ceramic composite with excellent thermal and dielectric properties is a promising LTCC substrate material.