Abstract: A modular mounting apparatus for substrate means bearing planar circuit means is provided and includes a design of components that assemble into a housing package for microcircuit modules with means for locating, supporting, interconnecting and housing them; in an interference free environment, i.e., provisions for moisture, radio frequency interference and electromagnetic interference sealing are provided. The apparatus provides a modular systematic and economical means of packaging for low frequency printed circuit boards to microwave frequency microcircuits.