burn-in

Burn-in is accelerated stress testing that subjects finished ICs to elevated temperature and voltage to screen out early-life failures (infant mortality) before shipping to customers. Concept: "bathtub curve" reliability—failure rate is high initially (infant mortality), decreases to steady state (useful life), then increases (wear-out). Burn-in accelerates infant mortality failures to remove weak devices. Stress conditions: (1) Temperature—typically 125°C (junction temperature); (2) Voltage—elevated VDD (1.1-1.2× nominal); (3) Duration—hours to days depending on product requirements; (4) Exercising—toggle logic to activate defects (dynamic burn-in preferred). Burn-in types: (1) Static burn-in—apply voltage and temperature, no signal toggle; (2) Dynamic burn-in—apply test patterns to exercise circuits during stress; (3) IDDQ burn-in—monitor quiescent current for defect detection; (4) Wafer-level burn-in (WLBI)—stress at wafer level before packaging (cost reduction). Failure mechanisms screened: (1) Gate oxide defects (weak spots break down); (2) Metal voiding (latent EM or stress migration); (3) Contact/via resistance (marginal connections fail); (4) Contamination-induced leakage. Burn-in economics: expensive process (equipment cost, time, energy, handling yield loss)—industry trend is to reduce or eliminate through: (1) Better process control; (2) Improved test coverage; (3) Voltage screening at test; (4) Statistical burn-in (test sample, not 100%). Requirements: automotive (zero DPPM demands extensive burn-in), consumer (may skip burn-in for cost), military (full burn-in required). Equipment: burn-in boards, burn-in ovens, pattern generators. Trade-off between burn-in cost and field failure risk drives product-specific burn-in strategies.