What is HASA (Highly Accelerated Stress Audit)?
HASA (Highly Accelerated Stress Audit) is HASS applied to a statistical sample of production instead of 100% of units. Production moves to HASA once the process is stable and the screen has stopped finding defects, and goes back to 100% HASS when something changes.
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HASS screens every unit; HASA screens a sample
HASS applies a short, aggressive stress profile, derived from HALT limits, to every production unit. HASA uses the same screen on a statistical sample per lot or per period. The screen itself does not change; how many units go through it does.
When to move to HASA
Start by screening 100% of production. Once HASS yield is high and stable, typically after sustained, near-zero relevant defect rates over a meaningful volume, the screen may move to an audit basis. Define the sampling plan, the escape-risk basis for it and, critically, the conditions that send production back to 100% HASS. Switching too early forfeits the protection HASS provides.
Whether HASA fits depends on the product:
| Your situation | What you need |
|---|---|
| High volume, stable process (automotive, consumer electronics) | HALT, HASS at launch, then HASA once the process proves stable and the screen stops finding defects |
| Low volume, high mix, high value (aerospace, defense, medical) | HALT, plus HASS on every unit: a field failure costs far more than screening, and 100% screening is practical at low volume |
When to go back to 100% HASS
HASA is a reduction in cost, not in vigilance. Revert to 100% HASS on any relevant defect found in audit, a process or component change, a new supplier, or field-return signals. A change of solder paste, a different build location or a process drift can all bring failures back, and the screen is often the first place they show up.
In the standards
GM’s GMW8287 names HASA in its title, “Highly Accelerated Life Testing (HALT), Highly Accelerated Stress Screening and Auditing (HASS/HASA)”. It describes HASA as the same process as HASS, operated on an audit basis instead of on 100% of production, and calls the transition from one to the other the GlidePath. The standards guide summarizes it.
The short answer
What is HASA?
Highly Accelerated Stress Audit: the HASS profile applied to a sample of each production lot rather than to every unit. It is appropriate once the manufacturing process has proven stable and the screen has stopped yielding failures.