Abstract: A method of assembly of at least two ceramic components each having at least one flat surface, as applicable in particular to microwave equipment and encapsulation modules for microwave semiconductors. The starting components are made of ceramic material which has been pre-fired, or in other words heated to about 1500.degree. C., and are therefore rigid. The components are no longer joined together by means of a glass paste or a brazed joint between metallized parts but are heated to over 1700.degree. C. The impurities which are present in the ceramic material in a proportion of 1 to 10% serve as a flux and produce an autogenous weld between the two components. Prior to assembly, the ceramic components can be provided with metallizations such as electric tracks on condition that these metallizations are refractory.

Abstract: The substrate is formed by a plate of boron nitride having a composition of 42% B, 53.5% N.sub.2, containing between 1.5 and 2.5% O.sub.2, and 1.5% Ca. The surface is increased in hardness and made non-friable by deposition of a glass film to a depth within the range of 10 to 15 microns. This deposit permits surface metallization and ensures cohesion of the boron nitride grains.