HASS – Highly Accelerated Stress Screening
To find manufacturing and production process induced defects, many companies use HASS testing before those products are released to market. HASS testing can be a powerful testing tool for improving a product’s reliability, and help to reduce warranty costs while increasing customer satisfaction.
In this diagram (left) ESS (Environmental Stress Screening) is referenced to show its ineffectiveness against product to be shipped (A HASS Screen Diagram).
Once a product has undergone HALT, HASS can be used as part of the production process. The goal of a HASS test is to induce failure modes that can be inherent or introduced in the production process. HASS testing will serve as an effective method to find screening failures that may have gone undetected in the burn-In testing process during production. A product that passes normal production tests but fails in a HASS would have probably failed early after product release, and thus increasing warranty costs.
HASS is an acronym for Highly Accelerated Stress Screens after the industry use of the term “Enhanced ESS”. These screens use the highest possible stresses (frequently well beyond the “QUAL” level) in order to attain time compression in the screens. Note that many stimuli exhibit an exponential acceleration of fatigue damage accumulation with stress level, and so a drastic reduction in screening equipment and manpower is obtained by the use of higher stress levels. The screens must be, and are proven to be, of acceptable fatigue damage accumulation or lifetime degradation using Safety of HASS techniques.
HASS is generally not possible unless a comprehensive HALT has been performed as, without HALT, fundamental design limitations will restrict the acceptable stress levels to a great degree and will prevent the large accelerations that are possible with a very robust product. It has been proven that HASS generates extremely large savings in screening costs because much less equipment (shakers, chambers, monitoring systems, power and liquid nitrogen) is necessary due to time compression in the screens. HASS, too, is discovery testing as compared to success testing.
CVG Strategy can implement and integrate a HASS Program once HALT has been concluded, and help to improve your production reliability dramatically.