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This section describes reliability related to the
factors established in the Scope section of this document/database. Use this
section for reliability requirements of Discrete Semiconductors.
The Reliability Prediction of Electronic Handbook,
MIL-HDBK-217F Notice 2, is used as the guideline for establishing the
probability for Discrete Semiconductors. This handbook is still the best tool to
use when establishing probability for these type parts.
Since the military allows the use of non-military parts
in its systems, the risk to satisfactory operation has increased
dramatically. Discrete semiconductors
are usually employed in key application functions. Observing temperature ratings and the ability
to dissipate heat from such parts are critical to maintaining function. Using non-military parts involves a trade-off
between their material and construction, and their durability. Lower quality material typically raises the
parts’ temperature and poorer construction inhibits efficient heat
dissipation. The combination of these
two characteristics has the net effect of reducing part reliability and expected
life. To operate at a performance level satisfactorily, use QML-19500
manufacturers and JANTX level parts, as a minimum.
Semiconductor Life (Time)
The environmental categories described in detail in the Scope
section of this document/database categorize part life as being either 5, 10, or
20 years. The derating recommendations in Discrete Semiconductor Derating section take part quality levels and application environments
into account. This will assist the designer in selecting the correct part for
the application. The only parts designed to last over 5 years and up to 20 years
are QML-19500 parts.
Semiconductor Operating Conditions
Military (QML) parts are designed to withstand the extreme
environmental conditions of military applications whereas non-military parts are
designed for much lower environmental levels.
Temperature, shock, and vibration are the most important environmental
conditions; moisture is less so due to the typically smaller package size. Even in a low vibration or shock application,
a poorly bonded non-military part can fail causing a catastrophic failure. Assessment of non-military parts and/or an
evaluation of the manufacturer is recommended for risk