Printed Wiring Assemblies (PWAs)
Lack of staking material causing lead breakage

High-cycle metal fatigue, induced during vibration testing, caused the failure of the anode lead wire of this tantalum capacitor. Deformation at the flat spot work-hardened the metal of the anode lead wire and made it more brittle. The flat spot also narrowed the wire diameter-creating a weak spot susceptible to flexure. In addition the mass of the capacitor was not designed to be supported by axial wires of only .036 in diameter. The apparent lack of staking material, or failure of the staking material to properly bond with the Mylar sleeve around the capacitor contributed to the failure.

Reference :
NASA-STD-8739.3
7.2 Preparation of Conductors
3. Damage to Conductors. After removal of the conductor insulation, the conductor shall not be nicked, cut, or scraped to the point that base metal is exposed. Part leads and other conductors that have been reduced in the cross-section area shall not be used. Smooth impression marks (base metal not exposed) resulting from tool holding forces shall not be cause for rejection.