High Temperature Electrical Shorts in Printed Wiring Boards

Electrical shorts were noted on power supply printed wiring boards during production burn-in tests. These shorts were limited to the higher temperature areas of the boards which were biased at ~ 360 Vdc. The failure mechanism is not related to conductive anodic filaments (CAF) and has not been reported widely in the literature.

The result of this study indicates that failures are dependant on the gaseous ionization of microscopic voids (streaks) within the glass fibers that are imbedded in the printed wiring board. In addition, the data also suggests that these epoxy boards are much worse than their polyimide counterpart.

Follow-on work will address these details in more depth. It is expected that this recent data will be incorporated into design guides for boards used in these higher temperature and voltage situations. This presentation will discuss the details of the failure mechanism, accelerated life tests and the microscopic defects in the board material.