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Physics Based Reliability Qualification
Yizhak Bot, BQR Reliability Engoineering Ltd,
Prof. Joseph B. Bernstein, Center for Reliability Physics and Failure Analysis,
Department of Electrical Engineering, Ariel University
Physics of failure studies have demonstrated that multiple failure causes occur during
normal operation of electronics. Most modern advanced devices will fail after only a few
years of operation, exhibiting a random end-of-life behavior that can occur far more
frequently than published expectations. Our new initiative is dedicated to understanding
reliability physics and performing advanced life testing of the multiple mechanisms and
their interactions that limit the useful life and results in failures of commercial electronic
systems. Our goal is to develop application specific reliability qualifications used in
design for reliability and to develop a tool for designers to incorporate reliability together
with performance as part of the system qualification.
The standard industrial approach to accelerated testing continues to be based on the
assumption of a single failure mechanism. In an ideal case, where only one mechanism
overwhelms other competing mechanisms, this methodology is well founded. However
today, in our push to faster and more complex systems on a chip designs, we have found
that this methodology falls far short of expectations for reliability qualification. Hence,
our reliability assessment must be more sophisticated and consider all the root cause
mechanisms of failure simultaneously.
Our new approach to lifetime and reliability calculations is through modeling failure
mechanisms as proven by accelerated testing of commercial parts. We analyze failures of
the components and compare the mechanisms that we model in the laboratory to be sure
that our models accurately reflect the true physics of failure responsible for unreliability
in order to better control their effects. We isolate the mechanisms using specific
accelerated tests and incorporate these models into a system reliability matrix. We
perform a trade-off analysis as part of the design parameters where we can tailor the
reliability of a system to meet the performance and reliability specifications before the
system is built and in the field. The result will be a more accurate and correct reliability
assessment compared to the current approach for building in reliability.