Printed Wiring Assemblies (PWAs)
Vibration-induced failure of electric component leads

The above design was reported to have experienced catastrophic component failure during vibration testing, resulting in fractured and broken component leads of heatsink-mounted powered devices. The above photograph of the failed assembly clearly shows a pattern of damage consistent with repeated movement and flexure of the components. The primary cause of the unwanted movement was attributed to a design decision, in which the heatsink was allowed to "float" with respect to the printed wiring assembly.
A design change, which mechanically bonded the heatsink and printed wiring assembly together, significantly reduced the incidence of component lead failures during vibration test.

Reference :
NASA-STD-8739.3,
4.3. Reliable Soldered Connections
1. Reliable soldered connections result from proper design; control of tools, materials, processes, and work environments; use of properly trained and skilled personnel; and careful workmanship.