||TEOOO-AB-GTP-020A: Environmental Stress Screening Requirements and Application Manual For N
4. Thermal Stability:
- Thermal Stability is considered to have occurred when the electronic
part with the largest thermal mass (excluding magnetics and
connectors) or non-metallic portion of the PWB surface is within 5°C
of the Temperature Range Limits.
- Measurement shall be by a thermocouple mounted directly on the
electronic part or PWB surface. The thermocouple shall be insulated
from the chamber air.
5. Dwell Time at Temperature Ranee Limits:
- Dwell Time at the upper and lower Temperature Range Limits need only
be long enough to reach Thermal Stability (as defined above).
6. Failure Free Temperature Cycle:
- A functional test shall be performed after the PWA level
TCSS. If a PWA RVSS is to be performed, the functional test
may be delayed until after the RVSS.
- Failed PWAs shall be repaired/reworked.
- Repaired/Reworked PWAs, if not subjected to subsequent TCSS at a
higher indenture level, shall be subjected to an additional
temperature cycle followed by a functional test. Failed PWAs shall
repeat this sequence no more than two times. In the event that a PWA
fails the second failure free cycle for the same reason as the first
failure free cycle, recommended corrective actions/alternative
approaches shall be provided to NAVSEA. Application aspects are
discussed in Section
- Repaired/Reworked PWAs, when subjected to subsequent TCSS at a
higher indenture level, shall be reintroduced into the production
flow process without requiring a failure free cycle.
7. Performance Monitoring:
8. Power On/Off Cycle:
- Input power or power on/off cycling not