Component lead wire strain relief for random vibration environments

Printed circuit boards exposed to severe random vibration environments for prolonged periods often experience fatigue failures. The failures occur in connection with severed circuit traces, fractured solder joints, fretting corrosion of connector contact pins, or broken lead wires on electronic components. The present investigation is mainly concerned with the latter cause of failure. Aspects of lead wire geometry are defined and factors contributing to the development of bending stress in the lead wires are examined. Such factors are related to environmental load applications, board-specific characteristics, and component-specific characteristics. Attention is given to effects of component location, questions concerning the selection of the proper strain relief, the effects of lead length on stresses, the proper component orientation, and the characteristics of different types of components. A sample problem is also discussed.