Cooling means for circuit assemblies each including hollow structures spaced apart in a container

A circuit assembly having a plurality of subassembly units, each subassembly unit having a planar substrate, with constituent components of the circuit assembly being mounted on the substrates, the plurality of subassembly units being connected together to complete the required circuit, the circuit assembly also having a plurality of identical, substantially enclosed, hollow structures, the substrate of each subassembly unit considered individually comprising at least part of a wall of a substantially enclosed hollow structure, at least one substrate being included in each such structure, the constituent plurality of structures being mounted spaced apart from each other within an at least substantially enclosed container, one other wall of each structure providing part of a closure wall for the container, the container closure wall defining passages communicating with the interiors of the structures, the other container walls defining at least one further passage communicating with the regions within the container surrounding the structures, the walls of the structures within the container defining holes communicating with both the interiors of the structures and the regions within the container surrounding the structures, and there being provided a supply of cooling fluid connected to at least one passage defined by a container wall, there being a flow of cooling fluid through the container, between the interiors of the hollow structures and the regions within the container surrounding the structures, the arrangement being such that the holes defined by the walls of the hollow structures within the container cause the cooling fluid to flow directly over said components of the circuit assembly which are spaced from the holes and which generate heat, each of the hollow structures having a plurality of spaced, readily removable portions providing the holes when removed for the flow of cooling fluid between the regions within the container surrounding the hollow structures, and within each hollow structure.