HALT stands for “Highly Accelerated Life Test”. It is a process applied during the development phase of a new product, to validate design robustness. It is most commonly used to identify potential weaknesses in electrical and electronic assemblies.
Following HALT appropriate design modifications are made so that volume manufacturing can begin with a mature product design, thus minimizing costly warranty issues and potentially disastrous product recalls.
The fundamental principle is to apply stepped applications of increasingly powerful environmental stresses until latent (i.e. hidden) defects are precipitated; these are then rectified and the modifications revalidated.
If a product has an intrinsic weakness, exposure to day-to-day operating conditions will eventually cause it to fail at that point of weakness. By careful application of increased stress levels in HALT, the time for that same failure to occur is dramatically reduced.
Very few product samples are needed and the process can be competed very quickly.
The most commonly applied stresses (but not exclusively) are thermal and broadband multi-axis random vibration. These are used individually and then in combination.
There is no Industry Standard for HALT but the following stresses are usually applied to one or more functionally monitored test specimens until they cease to function:
- Progressive reduction in temperature to determine the lower operational limit and then the lower destruct limit
- Progressive increase in temperature to determine the upper operational limit and then the upper destruct limit
- Progressively more stressful thermal cycling at high, linear, rates of change of temperature
- Broadband random vibration at increasing intensity levels
- A combination of thermal and random vibration stresses
At each stage when a failure occurs, root cause analysis is performed, corrective action is implemented and the process continues until the fundamental limit of the product technology is reached.