What is HASS?
Highly Accelerated Stress Screening (HASS) techniques are incorporated during the production phase to find manufacturing process defects that could cause product failures in the field.
- Screening process exposes latent defects in components and assemblies
- Used during production to ensure ongoing product quality and reliability
- To be effective, screening must be customized to the product being tested
- Safety of screen insures sufficient life remains for end-user requirements
The HASS Process
HASS uses accelerated stresses (beyond product specifications and as determined appropriate by earlier HALT testing) in order to detect product defects in manufacturing production screens. The accelerated stresses of the HASS program shorten the time to failure of defective units and therefore shorten the corrective action time and the number of units built with similar flaws. Many issues caused by process changes after HALT screening were previously seen only as early life failures in the field. With an appropriate HASS implementation, these defects can now be detected and corrected prior to customer shipment.
HASS is generally not recommended unless a comprehensive HALT has been performed, since without HALT, fundamental design limitations and flaws will restrict stress levels that can be applied in the HASS process. HASS can generate significant savings in screening costs as less equipment (shakers, chambers, monitoring systems, power and liquid nitrogen) is necessary due to time compression in the screening process. As with HALT, HASS is discovery testing as compared to compliance testing.
References: Accelerated Reliability Engineering, Gregg K. Hobbs, Hobbs Engineering, 2005.