Abstract: In order to provide a simple and expeditious method of manufacturing a heat exchanger which comprises a plurality of heat exchange tubes in substantially parallel, spaced apart stacked relationship, with the end portions of each heat exchange tube being sealingly disposed through a respective pair of aligned apertures in two spaced end walls, the end portions of each heat exchange tube are urged in one direction through the apertures in resiliently deformable plates of the end walls, the end portions of the tube being an interference fit in these apertures in the resiliently deformable plates so that the edge portions of the resiliently deformable plates bounding the apertures therein are resiliently deformed.

Abstract: The invention concerns micro-circuit arrangements in which two micro-circuits each consisting of an assembly of components and/or micro-strip conductors within individual compartments, are interconnected. In the arrangement provided by the invention the individual compartments have a common wall in which a gap is provided adjacent the ends of a micro-strip conductor in each micro-circuit and a bridge piece is provided to fit into the gap, which bridge piece consists of a block of dielectric material carrying a conductive member which connects with both micro-strip conductors adjacent the gap.