MIL STD- Failure Rate Sampling Plans and Procedures (2005)

Keywords failure rate military standard sampling plans and procedures


4.1 FR levels.
a. FR levels are related to operation of the part at the stress level specified by the applicable ER specification.
b. Provisions are made for FR levels ranging from 1.0 to 0.001 percent per 1,000 component part hours. In the event the existing FR level of a current product is higher than 1.0 percent, an additional level (level “L”) shall be added which will represent the state-of-the-art for the part.
c. Although the failure is expressed in percent per 1,000 hours (%/1,000 hr) throughout this standard, sampling plans and statistical tables may be used for FR levels expressed either in terms of percent per 1,000 cycles, operations, or in terms of duty cycle and stress level.
d. Where a FR level is required for periods other than 1,000 hours, an appropriate conversion factor may be applied.
Example: 1%/10,000 hours is equivalent to 0.1%/1,000 hours, or when specifying %/10,000 hours, the unit-hour requirement is to be multiplied by 10.
e. Tables are provided to show the relationship between true failure rates and selected confidence levels.

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1.1 Purpose.
This standard provides procedures for failure rate (FR) qualification, sampling plans for establishing and maintaining FR levels at selected confidence levels, and lot conformance inspection procedures associated with FR testing for the purpose of direct reference in appropriate military electronic parts established reliability (ER) specifications. Figures and tables throughout this standard are based on exponential distribution. Weibull distribution will be acceptable in certain components such as capacitors. Use of Weibull distribution for any component must be approved by the qualifying activity. This standard also provides guidance to specification writers in the use of this standard (see appendix A) and references material for users of ER parts.

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