Abstract :
It is pointed out that certain basic design disciplines are prerequisite to more effective mechanized use of printed wiring. The 25-rail layout grid is described as one of these basic prerequisites. Specification SCL-6225, "Design Requirements for AutoSembled Army Signal Electronic Equipment," is presented as a basis for the present recommendations. The concept of "projected component volumes" is introduced: to make component-parts dimensions compatible with printed-wiring requirements; and to provide both a design guide, and a convenient assessment, for volumetric efficiency. Effects of hole, terminal pad, and conductorspacing variations are discussed. Component-part height variation is charged with the major contribution to poor volumetric efficiency, and corrective measures are suggested. Dimensions of length, height, and width are all recommended in building-block steps, compatible with printed wiring of the present, and micro-modules of the future; and certain preferences are given. Specification SCL-6254, "Modular Dimensioning of Electronic Parts," is announced. It is concluded that these recommendations will form a logical extension of the large equipment module to provide greater ease of automation and higher volumetric ef- ficiencies.
