Screening Stage
Production quality verification involves running a second electrical test on components after they have completed thermal and electrical stress cycles. Typically, a post burn in retest identifies and removes devices that have failed or drifted out of specification during the stress phase of the manufacturing process. This screening step acts as a filter to prevent infant mortality failures from escaping to the assembly line.
Process Control
Automated test equipment executes the second round of tests using identical or tighter guard bands than the initial test. If a device has undergone a parametric shift beyond allowable tolerances, it is discarded even if its absolute values still fall within general specification limits. This procedure ensures long term reliability in high reliability fields like automotive or medical electronics.
Test Optimization
Thermal stress induces changes in marginal contacts and weak dielectric structures that would otherwise pass standard room temperature checks. Gathering data from this second run allows the manufacturing line to identify wafer lots that are highly susceptible to stress induced failures. This analysis helps in modifying the preceding steps or adjusting the stress duration to optimize overall production yield.
When the failure rate of the retest exceeds a baseline percentage, the entire batch is quarantined for further failure analysis. This action prevents the shipment of suspect parts.
