For Bellcore/Telcordia and MIL-HDBK-217
Methodology - The Equations, Failure Rate, MTBF & FITs
Limitations of Reliability Prediction
What is the Difference Between Quality and Reliability?
The device failure rates contained in this document reflect the expected field reliability performance of generic device types. The actual reliability of a specific device will vary as a function of the degree of effort and attention paid by an equipment manufacturer to factors such as device selection/application, supplier selection/control, electrical/mechanical design margins, equipment manufacture process control, and quality program requirements.
The quality levels described below are not intended to characterize or quantify all of the factors that may influence device reliability. They provide an indication of the total effort an equipment manufacturer considers reasonable to expend to control these factors. These quality levels also reflect the scope and depth of the particular equipment manufacturer's component engineering program.
QUALITY LEVEL 0
level shall be
assigned to commercial-grade, reengineered, remanufactured, reworked,
or gray-market components that are procured and used without device
qualification, lot-to-lot controls, or an effective feedback and
action program by the primary equipment manufacturer or its outsourced
lower-level design or manufacturing subcontractors. However, steps must
been taken to ensure that the components are compatible with the design
This level shall be assigned to commercial-grade components that are procured and used without thorough device qualification or lot-to-lot controls by the equipment manufacturer. However, (a) steps must have been taken to ensure that the components are compatible with the design application and manufacturing process; and (b) an effective feedback and corrective action program must be in place to identify and resolve problems quickly in manufacture and in the field.
QUALITY LEVEL II
This level shall be assigned to components that meet requirements (a) and (b) of Quality Level I, plus the following: (c) purchase specifications must explicitly identify important characteristics (electrical, mechanical, thermal, and environmental) and acceptable quality levels (i.e., AQLs, DPMs, etc.) for lot control; (d) devices and device manufacturers must be qualified and identified on approved parts/manufacturer's lists (device qualification must include appropriate life and endurance tests); (e) lot-to-lot controls, either by the equipment manufacturer or the device manufacturer, must be in place at adequate AQLs/DPMs to ensure consistent quality.
QUALITY LEVEL III
shall be assigned to components that meet
requirements (a) through (e) of Quality Levels I and II, plus the
(f) device families must be requalified periodically; (g) lot-to-lot
must include early life reliability control of 100 percent screening
(temperature cycling and burn-in), which, if the results warrant it,
reduced to a “reliability audit” (i.e., a sample basis) or to an
“reliability monitor” with demonstrated and acceptable cumulative early
values of less than 200 ppm out to 10,000 hours; (h) where burn-in
used, the percent defective allowed (PDA) shall be specified and shall
exceed 2%; and (i) an ongoing, continuous reliability improvement
be implemented by both the device and equipment manufacturers.
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Last modified: 5/18/20
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