scope:

Description of Driving Event:

A battery charger design was reported to have experienced catastrophic component failure during vibration testing, resulting in fractured and broken component leads of heatsink-mounted power devices. A photograph of the failed assembly (Fig. 1) clearly showed 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 the printed wiring assembly together, significantly reduced the incidence of component lead failures during vibration tests.

A visual examination of sample components supplied to JSC suggested that the use of unapproved tooling and processes during the component lead forming process was a contributing factor to the observed fractured and separated leads, with numerous sample components exhibiting leads with cracks (Fig. 2). Discussions with the vendor indicated that metallic tools (including a screwdriver) were employed to form the leads. Subsequent improvement in tooling and processes resulted in smoothly formed lead bends, without fractures or significant tooling marks.