MIL-STD-690-SUP Failure Rate Sampling Plans and ProceduresThis 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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MIL-STD-690D

5.  DETAILED REQUIREMENTS

5.1  Procedure I,  "Qualification at the initial FR level".  Qualification at the initial FR level shall be predicated upon accumulation of valid data meeting the requirements of 5.1.2a or 5.1.2b, as applicable.  FR tests shall be conducted for the specified duration and single sample size.  The qualifying activity may grant qualification at a FR level lower than that specified provided the manufacturer performs all tests required for initial qualification and submits valid data from current production which substantiates lower failure rates.

5.1.1  Applicable data.  Data shall be accumulated from sample units selected from a production run and produced with equipment and procedures normally used in production.  One of the prerequisites for valid data is that all lots produced during the production period are represented.  The data shall be from the same product in current production; i.e., data from products of preceding designs shall not be acceptable.

5.1.2  FR sampling plans (FRSP).

a.        Single sampling plans based on a 60 percent confidence level are provided in table I (see table A-I of appendix A).

b.        Single sampling plans based on a 90 percent confidence level are provided in table II (see table A-I of appendix A).

TABLE I.  FRSP-60.

1/    For FR level expressed in terms other than %/1,000 hour, see 4.1c and 4.1d.

2/    Where a FR level greater than 1.0 percent is required, level "L" shall be specified and the cumulative unit hours computed as shown.

TABLE II.  FRSP-90.

1/    For FR level expressed in terms other than %/1,000 hour, see 4.1c and 4.1d.

2/    Where a FR level greater than 1.0 percent is required, level "L" shall be specified and the cumulative unit hours computed as shown.

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