Optimum Mounting Locations for Shock-Protection of Fragile Components

Clattering motion that occurs when flat objects strike the ground at an oblique angle is studied through a simple model of a rigid bar with arbitray but symmetric, mass distribution and coefficient of restitution. The maximum velocity changes, or velocity shocks, that occur at various locations of the bar as it clatters to rest, are presented. It is shown that different parts of the bar can be subjected to sequences of velocity changes that are both higher, and lower, than those encountered in a single clatter-free impact. The implication that the drop-tolerance of an electronic product can be increased by configuring it to have "safe zones" - where the velocity shocks are lower - for the placement of fragile components, is analyzed. It is shown, through example, that a significant safe zone can be created in the center of the product by configuring it to have a low moment of inertia and by minimizing coefficient of restitution. The results of this study are applicable to shock-protection of network components and communication/computing products currently of interest. This includes low-cost ratio modules like "Bluetooth," DWDM packages, MEMS devices as part of larger systems, etc.