Abstract: The invention concerns an MCM type high-density assembly of integrated circuits having a high reliability by virtue of its design and the means employed in its implementation. The essential feature of the assembly is the presence of one or more interconnection substrates in addition to at least one substrate carrying a plurality of unencapsulated electronic chips connected to the interconnection substrate(s) by conventional microwiring techniques, preferably through one or more apertures in the substrates. The interconnection substrate(s) is or are advantageously of the multilayer type. The assembly is adapted to be encapsulated thereafter in a hermetically sealed case in the manner that is standard for MCM.