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Reliability is the probability of a part performing its specified purpose for the period intended under the operating conditions encountered. This definition stresses three elements: performance, time, and operating conditions. These factors play an important role in the part’s reliability.

a.  Performance is satisfactory operation in accordance with clearly specified, described, or defined criteria. The military uses performance specifications (e.g., MIL-PRF-38535 for Microcircuits or MIL-PRF-19500 for Discrete Semiconductors) for part types described in this document/database. Performance specifications are described in each section.

b.  Time is the period during which a specified degree of performance is expected. It is the cornerstone of reliability because without a knowledge of the probabilities of individual parts functioning for a given time, there is no way of assessing the probability of the system performing a function for a given time.”

c.  Operating conditions comprise the environment in which a part is expected to function. Typical factors are temperature, humidity, shock, and vibration. MIL-HDBK-338B, Electronic Reliability Design Handbook, should be used in conjunction with this document/database.