Differences between HALT and HASS testing profiles

HALT and HASS are two essential tools in a robust reliability program, but they serve very different purposes at different stages of a product's lifecycle. Understanding their differences ensures each test is used to maximum effect and helps deliver durable, high-quality products to market.

Purpose and Timing

• HALT (Highly Accelerated Life Testing):

  • Used during the R&D and prototype phase.

  • Designed to intentionally push the product beyond its specifications, uncovering fundamental design and process weaknesses.

  • Not structured as a pass/fail test, but as a discovery tool for improving design robustness.

• HASS (Highly Accelerated Stress Screening):

  • Employed in production, after the design has passed HALT.

  • Stress levels are aggressive but within known safe margins—these margins are determined from earlier HALT results.

  • Focuses on screening out manufacturing defects before delivery, protecting customers from early failures.

Stress Profiles and Test Outcomes

• HALT:

  • Applies rapidly increasing stresses—temperature extremes, vibration—until the product fails or is destroyed.

  • Documents all failure modes, operational limits, and destruct limits so engineers can redesign or reinforce those weak points.

  • Outcome: recommendations to improve product durability, define safe working and destruction limits.

• HASS:

  • Applies the combined environmental stresses defined by HALT—but stops short of destruction, staying within limits that won't cause irreversible damage to good products.

  • Any unit that fails during HASS is removed or investigated for potential process issues, component drift, or other manufacturing faults.

  • Outcome: defective units are identified and filtered out, assuring reliable product delivery.

Process Overview

Feature	HALT	HASS
Objective	Reveal design and process weaknesses	Screen out manufacturing defects
When Used	R&D, prototyping, early design	Production, just before delivery
Stress Levels	Beyond operational/destruction thresholds	Aggressive but below destructive thresholds
Test Outcome	Insights for improvement, design margins	Pass/fail: units must survive or are rejected
Frequency	Once or per major design iteration	Routinely for each production batch
Typical Result	Design updates, improved robustness	High reliability, fewer out-of-box failures

Complementary Role

HALT and HASS are not alternatives. HALT defines what the limits are and ensures a rugged design; HASS takes that information to optimize production screening. Used together, they form a closed-loop system that boosts both product robustness and manufacturing quality, minimizing failures both before and after launch.

By applying these two strategies serially, companies can revolutionize their product reliability results and consumer satisfaction.