Design of an optimal plan for an accelerated degradation test: a case study

Purpose – To design an optimal accelerated degradation test (ADT) plan for light emitting diodes (LEDs). Design/methodology/approach – This paper presents a method for the optimum planning of ADTs. The method is applied to the design of an optimal plan for LEDs. An analytical method is developed for obtaining the optimal allocations of test units to minimize the variance of the transformed life estimation at the use stress level; a simulation method is used to help select the optimal test plan and evaluate the test plans' properties. Optimal stress levels, and optimal allocations of test units to the stress levels are determined to minimize the mean squared error (MSE) of the estimated mean life of LEDs at the use stress level. Findings – Different test plans result in different accuracy. The optimal test plan provides the most efficient use of test resources. Research limitations/implications – This paper focuses on designing an optimal plan using two test stress levels. Future research may extend to multiple stress levels. Practical implications – With increasing emphasis on reliability in industry, products are made more robust, and few failures are observed in a reasonable test period. Therefore, assessing product reliability using ADTs becomes very useful. This paper fulfills the need to scientifically design plans for these tests to provide more accurate estimates of the designed‐in and manufactured reliability for the same amount of test resources. Originality/value – The methodologies developed in this paper can be used for other ADTs. This enables reliability and test engineers to get the most efficient use of their test resources.