Assessment is the most accurate way of predicting failure rate, but requires commitment and time. In the Highly Accelerated Life Test (HALT) approach to assessment, a number of prototype units are tested under as many conditions as possible, with cycling of temperature, input voltage, output load, and other impacting factors. HALT testing is based on a simple basic principle: to fatigue a component, printed circuit board, subassembly, or finished product, users can either stress it with lower levels of stress but for many cycles, or use a higher level of stress for a fewer number of cycles. Highly Accelerated Stress Screen (HASS) testing is an accelerated reliability screening technique which can reveal latent flaws not detected by environmental stress screening, burn-in, or other test methods. HASS testing uses stresses beyond initial specifications, but still within the capability of the design as determined by HALT. The combination of variable thermal and simultaneous vibration stresses, in conjunction with product specific stresses, finds those defects and marginal products that traditionally were seen as “out of box” infant failures. The stresses in HASS are more rigorous than those delivered by traditional approaches, so HASS testing substantially accelerates early discovery of manufacturing-process issues. Reliability engineers can then correct the variations that would otherwise lead to field failures and greatly reduce shipment of marginal product.