Abstract: An encapsulating case or box for hybrid circuits, able to operate in highly pressurized atmosphere, the components of the hybrid circuit being not subject to the action of pressure. For this purpose, said circuit is enclosed in a case taking the plane of the hybrid circuit substrate as the plane of symmetry, two half-shells made from an electrically insulating rigid material being arranged in symmetrical manner on the two faces of the substrate for creating a zero deformation area within the case. The electrical connections between the hybrid circuit and the connecting pins, outside the case and supported by the substrate are provided by flat metal conductors passing in the gluing plane to the substrate of a half-shell.