Proper application of environmental stress screening offers several benefits:
- Reduced overall life cycle cost
- On-time deliveries
- Improved reliability after delivery
- Improved user confidence and/or satisfaction
- Reduced support costs
- Improved readiness
- Improved production process
While these benefits far outweigh the costs of implementation, they do not come without a penalty. ESS must be implemented early in the program and closely supervised throughout. It will take time and commitment of the senior managers, because the benefits are long term but the requirements for people and funds occur early in the program.
ESS is normally conducted during the manufacturing
process to detect latent defects in parts and workmanship, but may also
disclose design limitations that were not detected during qualification and
engineering tests. In addition, there are distinct benefits to conducting ESS
during development as well. A considerable percentage of the failures
encountered during a reliability growth (test, analyze and fix) test program
may be caused by poor workmanship and defective parts. These
non-design-related failures can mask design-related failures, can cause
schedule slippage, and can adversely affect performance. By screening the item
prior to this testing, these adverse effects can be minimized. It is virtually
impossible to achieve design reliability without reducing to a minimum the
reliability degradation due to screenable flaws. Additional benefits are
presented in Table
2-1
.
