An engineering-of-failure approach to designing and executing an accelerated product qualification test

An Engineering-of-Failure approach to designing and executing an accelerated product qualification test was performed to support a risk assessment of a “work-around” necessitated by an on-orbit failure of another piece of hardware on the Mars Global Surveyor spacecraft. The proposed work-around involved exceeding the previous qualification experience both in terms of extreme cold exposure level and in terms of demonstrated low cycle fatigue life for the power shunt assemblies. An analysis was performed to identify potential failure sites, modes and associated failure mechanisms consistent with the new use conditions. A test was then designed and executed which accelerated the failure mechanisms identified by analysis. Verification of the resulting failure mechanism concluded the effort. MIL STD. 883C calls out several tests that are intended to assess the qualify of wire bonds used in packaged semiconductor devices. Unfortunately, these same tests do not necessarily assure the reliability of these same wirebonds under field use conditions. This is particularly true for missions that involve a significant number of thermal cycles either as a result of power cycles or environmentally induced thermal cycles. This paper concludes with a brief discussion of this and its implications