Full-scale development of an electronic assembly is a very complex process conducted by a multidisciplinary team. The process involves numerous professional skills, the main being: Electrical, Mechanical, Software, Component and Reliability engineering. Electronic assemblies designed for military applications, require high quality performance, long life cycle (storage and mission profiles) and operation in harsh environmental conditions. This paper presents main aspects of the mechanical design and the issues to be considered during the full-scale development process of electronic units used in military systems.