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PCBD-Sept2015

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36 The PCB Design Magazine • September 2015 While electronic reliability issues were widely suspected, but eventually ruled out as a root cause, the crisis revealed the challenges of evaluating, validating and investigating the reliability and safety assurance aspect of mod- ern, distributed and interactive vehicle controls systems that are equally taxing on OEMs, elec- tronic system suppliers and regulators. Meanwhile, in Europe, the new standard ISO 26262, "Road Vehicles—Functional Safety," defines an automotive-specific approach for de- termining risk classes and requirements for vali- dation and confirmation measures to ensure a sufficient and acceptable level of safety and reli- ability is being achieved. CAE Apps and Physics of Failure Reliability physics a science-based approach that is rapidly being employed in automotive electronics. It involves application of knowl- edge derived from physics of failure (PoF) re- search into how and why systems, components and materials fail. Knowledge of what initiates and propagates the failure mechanisms that re- sult in failure modes enables product designers to evaluate the potential failure susceptibility and risks of specific materials, structures and technologies in specific applications. This en- ables a virtual "analyze and optimize" form of reliability where susceptibility to failure risks can be rapidly identified early, at low cost, and designed out or mitigated, while the design is still on the CAD screen. This article will provide an introduction to reliability physics methods and tools and discuss how they can be em- ployed to optimize the product integrity (i.e., quality, reliability durability and safety [QRDS]) of vehicular electronics systems. A new set of CAE tools can help evaluate the safety and reliability of vehicular electron- ics models to meet these needs and support the new ISO standard. CAE modeling and simula- tion tools are now widely viewed as an automo- tive engineering core competency. These tools are needed to reduce new product development time in order to get products to the market faster, at lower costs by helping to design them right on the first attempt. Electrical and electronic (EE) engineers his- torically have gravitated to CAE tools for cir- cuit, functional and software analysis with less emphasis on structural analysis tools that were viewed as less essential to their field. However, as advancements in electronic technology have produced smaller and smaller devices that han- dle ever-increasing amounts of power and heat, the micro-structural integrity of wire bonds, micro-terminals and solder joints become in- creasingly important, especially in the auto in- dustry where the ability to endure 10–15 years of harsh environmental conditions is a require- ment. This is underscored by the fact that the majority of field failures of electronic modules are physical and structural in nature, related to items such as thermal over stress and fracture or fatigue of wires, solder joints, component ter- minals, wire bonds, and circuit board through- hole vias. Today, evaluating and achieving the struc- tural integrity, durability and reliability of au- tomotive electronic modules still primarily de- pends on traditional design-build-test-fix (D-B- T-F) reliability processes that employ a variety of environmental stress and usage durability tests of physical prototypes. The time and cost of building and testing prototype electronic com- ponents has been a limiting factor in efforts to accelerate the product development-validation process of automotive electronics. As vehicular electronic content continues to climb into and beyond the range of 70 to 80 modules per vehicle (on internal combus- tion engine vehicles), the burden of integrity feature " The time and cost of building and testing prototype electronic components has been a limiting factor in efforts to accelerate the product development-validation process of automotive electronics. " PHySICS oF FAIluRE DuRABIlITy SIMulATIoNS FoR AuToMoTIvE ElECTRoNICS

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