Accelerated Life Testing of COTS/NDE

Why Accelerated Step Stress?

• History is holding us back
• Probability estimating still dominates traditional electronic reliability thinking
• Test to limits + determine root causes + learn physics of failure + remove weak links

History of Environmental Stress Testing and Screening

• 1940 - 1960 Military Handbook 217
• 1960 - 1970 Burn-in, Willis J. Willoughby's NAVMAT P-9492
• 1980 - today AST, ESS and current best commercial practices surpass military reliability

Failure Mechanisms and Environmental Stress

• Components and stress stimuli
• Systems and stress stimuli
• Acceleration of electronic lifetimes; is MTBF a valid measure of electronics life?
• Wearout modes in electronics; if not MTBF, then what terminology to use?

Common Cause vs. Special Cause

• Common Cause Examples
• Special Cause Examples
• How HALT and HASS precipitate and detect common and special causes

Use of Stress in Design Evaluation and Improvement

• Benefits; limitations
• Types of Stress Stimuli
• Levels of stress

Environmental Stress Stimuli

• Thermal
• Vibration
• Combinations of stresses

Highly Accelerated Life Testing (HALT)

• How to perform a highly accelerated life test on electronic hardware
• When to use a single stimulus and when to combine stimuli
• How high a stress level is high enough?
• Are failures under high stress levels relevant to field reliability?
• What equipment is needed? What personnel?
• Step stress test at what point in the design for manufacture? At what assembly level?
• What data should we gather? How should we analyze it?"

Highly Accelerated Stress Screens (HASS)

• Development and determination of appropriate stimuli levels
• Proof of Screen - how test can insure we don't damage good products
• Highly Accelerated Stress Audits (HASA)
• Examples of electronic system HASS processes

Concerns and long term improvements in HALT and HASS

• When do we stop screening?
• How do we optimize our screen?
• Optimizing the vibration and thermal fixturing
• Feedback from screening and long-term process improvement

Other Beneficial uses of Environmental Step Stress

• Benchmarking suppliers - use step stress to select most reliable components
• Benchmarking competitors - use step stress to evaluate their quality and robustness
• Use stress to precipitate and detect intermittent defects in NDF (No Defects Found) boards

Summary and conclusion

Award of certificates