Highly Accelerated Life Testing (HALT) is an excellent and low cost approach for assessing the robustness of an electronic product; however, the potential variations in testing temperatures, vibration loads and shock prevent direct extrapolation of results to life data, precluding HALT from being a reliability predictor.
The HALT process introduces products to progressively higher stress levels in order to quickly uncover design weaknesses or unanticipated factors, like screw loosening. By identifying the failures and providing opportunities for correction, a HALT test provides significant advantages by:
- Finding flaws not usually identified prior to product testing
- Finding and improving design margins
- Reducing development time and cost
- Providing information for developing accelerated manufacturing and environmental screens (i.e., HASS and EES)
HALT v. Traditional Reliability Testing
A brief comparison of HALT and traditional reliability testing provides a better understanding of key differences.
- Gathers information on product limitations
- Focuses on design weaknesses
- Provides six degrees of freedom for vibration testing
- High thermal rate of change
- Loosely defined parameters, capable of on-the-fly modification
- Not a pass/fail test
- Results are the basis for manufacturing (HASS) and environmental (EES) screen tests
Traditional Reliability Testing
- Simulates lifetime of use
- Focuses on finding failures
- Provide a single degree of freedom for vibration testing
- Moderate thermal rate of change
- Narrowly defined parameters that are rigidly followed
- Pass/fail test, meaning if the product passes there is no further analysis done to improve design
- Results are not used in environmental screen tests (EES)
How does HALT work?
The objective of HALT is to expose a product to individual and simultaneous vibration and thermal cycling while in operational mode, ultimately causing product failure so the weakest link can be determined and improved. That weakest link is then modified to increase the reliability of the product, and tested again.
The process is cyclical, and repeated over the course of a few weeks until the fundamental limits of materials or testing equipment is reached:
- Stress: Initially applied at a low level, and progressively intensified
- Failure: The gradually increased stress level eventually causes failure
- Analysis: The failure is evaluated to determine the root cause
- Improvement: Temporary adjustments are made
- Repetition: Repeat testing
- Engineers understand relevant stressors and technology limits of the device tested
- Equipment that can test both individual and combined stresses
- Testing and failure monitoring while the product is running in a functional state
- The ability to perform a root cause failure analysis
Root Cause Prediction and Analysis
All HALT failure modes can be addressed through robust DfR activities. However, predicting HALT failure modes prior to testing is a practical efficiency, especially with a comprehensive tool like Sherlock Automated Design Analysis™ software.
Using the models and parameters developed for the intended HALT, Sherlock can provide early predictions of how HALT will fail, allowing for time- and money-saving design adjustments prior to actual testing.
Sherlock is also beneficial post-HALT. Once the testing is completed and a failure is identified, Sherlock is able to conduct a root cause analysis. Results are then used to direct modification for test parts and correct design flaws before running the next HALT cycle.
Sherlock provides a high degree of insight into design weak points and margins, maximizing HALT effectiveness by predicting the onset of failure prior to testing. Contact us today for more information. To learn more from DfR Solutions, watch our webinar, Coatings and Potting - A Critical Update. Just click the button below!