Aluminum nitride circuit board

Abstract

Disclosed is an aluminum nitride circuit board which is advantageously used as a carrier for a part emitting a large volume of heat, the substrate of the circuit board is a sintered aluminum nitride substrate which comprises a basal part and projection rising from the basal part and offering a surface for application of a metallizing composition, a metallized layer thereof is formed on the upper side of the projection by applying the metallizing composition thereon and forming the applied layer of the composition by firing, the metallizing composition applied on the upper side of the projection is prevented from sagging down the lateral side of the basal part owing to the step formed with the projection and the basal part, the preclusion of the otherwise inevitable sagging of the composition contributes greatly to improving the circuit board's voltage withstanding property. Owing to the curved surfaces formed in the rising part of the projection, the edge on the upper side of the projection, and the corner along the edge of the basal part, the production of the circuit boards enjoys a very yield and the circuit boards are projected against accidents due to the otherwise possible occurrence of cracks during service.