Specifications

Planning and Engineering Guide, Release TR5.0.x/TN6.0.x 17
Most of the requirements specified by Telcordia for the above-listed types of
configurations are for a per-channel availability of 99.999%.
As required by GR-418-CORE and GR-499-CORE, circuit pack failure rate predictions
are performed in accordance with the requirements of TR-332. Also, GR-418-CORE
and SR-TSY-001171 are used in the analysis of system availability and other reliability
parameters. The current predicted per-channel availability meets the 99.999%
requirement.
Reliability Development
During product development, reliability growth is achieved primarily through Highly
Accelerated Life Testing (HALT). HALT is a proactive technique to improve products
and field reliability, not to measure the reliability of the product. The stresses applied
during HALT far exceed the field environment, and are intended to expose the weak
links in the design and processes in a very short period of time.
These stresses applied during HALT include such things as:
• Exposure to temperature extremes from as low as -50º C to as high as +110º C, or
to the upper destruct limit
• Rapid rates of change of temperature, as high as 60º C per minute
• Omni-axial random vibration, up to 30 G’s rms or to the upper destruct limit
• Power cycling
• Internal voltage margining
• Varying clock frequencies
• Exposure to high humidity
Once failures are precipitated during HALT, corrective action is implemented in order
to increase the robustness of the product. The HALT process continues in an effort to
identify the next weakest link. This HALT corrective action cycle continues until the
fundamental limit of the technology is reached, at which point the robustness of the
hardware has been optimized.
Where HALT is used to improve the reliability of the product, standard, accelerated-life
testing is used to measure the reliability of the improved product. Prior to releasing
hardware to production, accelerated life testing is conducted on an operating system, at
60° C for 1500 hours (minimum), far exceeding the GR-418-CORE requirement of
117 hours at 50° C. One purpose of this testing is to simulate the first year of
operational life and determine by way of life test data, the product mean time between
failure (MTBF) and availability.
Reliability in Production
The production process includes a comprehensive suite of tests designed to ensure
optimum product reliability and performance in the field. This production testing
includes the following:
• Automatic X-ray inspection
• In-circuit test, with boundary scan
• Board-level functional test
•System test