Incorporating Field Reliability Changes
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Unitsâ€™ field performance may vary during the period of their reliability study. This requires using an early change detector to monitor the field reliability. Systematic monitoring of field failures ensures that adverse changes in the production process are identified quickly in order to avoid facing serious reliability and warranty problems. This early detection system also allows one to regularly update the test optimisation decisions which are made based on a test-field integrated cost model. This cost model evaluates the trade-off between time on an environmental stress test and additional warranty costs associated with field failures. This paper develops a reliability model that incorporates production test information with field reliability performance. This model then is integrated into a field reliability early detection system to allow one to regularly optimize the test duration that minimizes the test-field total cost. Environmental Stress Testing (EST) is the most common approach to precipitating latent defects during the manufacturing of electronic products. This testing consists of applying environmental stresses to the product. Typically these environmental stresses consist of cycling temperature between a high and low extreme, while dwelling at these extremes for specific periods of time. While temperature cycling is the most common approach, it is not the only one and other stresses such as vibration, humidity and power cycling can also be used. The products are generally monitored during the test so that any deterioration in performance is detected. The test may be terminated at a point where the latent defects have largely been removed. Determination of the optimum test duration has been traditionally based on the identification of the change point at which infant mortality has largely been removed from the units. The time-on-test is typically the only factor that influences this d! ecision. On the other hand, monitoring of changes in the pattern of failure field data is an important requirement of any reliability management program. It is imperative that a method be available for the reliability engineers to effectively monitor and detect reliability changes and to understand if the reliability of the product has changed significantly from what was expected. Systematic monitoring of field failures also ensures that adverse changes in the production process are identified quickly in order to avoid facing serious reliability and warranty problems. These kinds of problems are mainly caused by unanticipated failure modes, unknown changes in raw material, changes in operating environmental conditions, etc. This paper proposes a model that integrates the influence of the production test failures and the field performance including their respective costs into a single unified model. A field reliability deterioration early detection system is then integrated into the total cost model to optimize the test duration for the minimum total cost.
Keywords: RAMS 2010 Proceedings - Product Reliability - Reliability