Aluminum nitride (AlN) is an important material for electronic applications, such as heat sinks. Its thermal conductivity, which is higher than that of magnesium and similar to that of silicon or aluminium, is well matched to its low electrical conductivity (1000 Ohm m). The combination of these two crucial properties makes AlN an ideal substrate for heat-generating components, such as light-emitting diodes.

AlN powders are produced mainly via carbothermal reduction or direct nitridation of aluminium oxide and are characterized by high purity. In combination with a suitable sintering aid, the sintering process can result in dense technical-grade ceramics. However, the processing routes of conventional AlN technology only allow for the manufacturing of flat substrates with limited geometrical complexity.

The formation of a complex-shaped component with good thermal conductivity is therefore challenging. In order to produce AlN components with a high thermal conductivity, the density of the raw materials must be sufficiently high. Moreover, the wurtzite crystal structure of AlN must be free of foreign atoms that hinder phonon propagation. This includes oxygen impurities, which cause vacancies in the crystal lattice and scatter phonons.

In this article, the authors demonstrate that the sintering of commercial AlN powders using a novel suspension development allows the production of highly dense and homogeneous components with a high thermal conductivity. The density of 10 sintered discs was measured using the Archimedes method and the thermal diffusivity was determined with a laser-flash instrument (LFA) based on an Nd-YAG laser.