Pressure Calibration for the Standards Laboratory
(PRE 510)
Overview –Thermal Fatigue damage to electronics hardware
- Failure mechanisms and environmental stress
- Wearout modes in electronics – the life cycle bathtub curve
- Latent defects in systems and environmental stress
- Military Handbook 217 and thermal fatigue failure mechanisms
Constant Temperature, Power Cycling, and Thermal Cycling – What is important?
- TCE (thermal coefficient of expansion) and the effect of thermal transitions on material interfaces found in electronics
- Is it the total number of thermal transitions?
- Is it the thermal rate of change?
- Or is Accelerating of chemical reactions is more effective at discreet component levels?
Lifetimes of electronic hardware – effects of thermal stress on defects
- Testing to find thermal weak links
- Flowchart for Step-Stress limit testing
- When to use thermal cycling and when to use constant elevated temperature
- Are failures under high levels of thermal cycling relevant to field reliability?
Test Plans - Development and determination of thermal stimulus levels
- Screens that find the majority of defects
- Insuring that significant amount of thermal fatigue life is not used
- Examples of electronic systems Accelerated Stress Test (AST) processes
Concerns and long-term improvements in Accelerated Stress Testing
- When do we stop screening?
- How do we optimize our screen?
- Optimizing our thermal cycling
- Feedback from screening - long term process improvement
Prediction from Thermal Fatigue Analysis
- Finite element analysis for wear-out modes
- Prediction of single failure mechanisms in electronic hardware
- The complexity of wide variations of solder, physical structures and fatigue prediction analysis
The advantages and limitations of testing for thermal fatigue weaknesses
- What is the goal of testing – discovery or quantification?
- Combined environments may be less stressful for some electronics structures
- Special cause vs. common cause latent defects and thermal fatigue life.
- Case studies – products with low thermal margin
Summary and conclusion
