Engineering analysis of module-populated printed circuit cards subjected to torsion is pursued by approximate engineering analysis, numerical (finite element), and experimental means. The engineering theory utilizes a simplified method of evaluating the torsional stiffness and maximum lead force, the latter found at the module corners. Finite element methods are used to check these values for circuit cards with a wide variety of module configurations, starting from a single-module to sixteen PLCC modules, having 44, 68, and 84 J-leads. An experimental torsion apparatus is used to obtain data for further comparison with the former approaches, and for getting data from the geometrically nonlinear (large deflection) range.

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