MIL-STD-690 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

w/ CHANGE 1

5.3.1 Applicable data:

a. Data from all FR tests underway or combined during the applicable qualification maintenance period (see

5.3.2) shall be applicable. Only that portion of the data generated during the maintenance period shall be applicable. Specifically the sources of these data are:

(1) Data from initial qualification samples that were maintained on test for extended FR testing (see 5.1.3). (2) Data accumulated from samples subjected to the FR tests specified for lot conformance FR inspection

when this procedure is specified (see 5.4). This includes both data from the relatively short time lot

conformance FR test as well as the data generated from those samples continued on the extended FR

test.

(3) Data accumulated from samples subjected to extended FR test in those specifications where lot conformance FR inspection is not specified. In these specifications, test samples shall be selected from each inspection lot. These samples shall be accumulated and placed on the specified extended FR test at least once a month or on a lot by basis. A minimum sample size from each lot shall be specified, however, the manufacturer may increase this sample size so that the unit hours generated within the specified qualification maintenance period meet the applicable requirements of table IV.

b. During the FR tests, parameter measurements shall be made periodically as specified. The data so accumulated since previous measurements shall be recorded and added to the total unit hours accumulated from the beginning of the qualification maintenance period. Data shall be recorded from all samples on test during the maintenance period whether or not they are from inspection lots formed during this period.

c. The data shall be representative of the styles and ranges of values produced over the production period covered by the applicable maintenance period.

d. Data from FR tests completed during previous qualification maintenance periods shall not be used (this data may be used for extension of qualification to a lower FR level).

5.3.2 FR sampling plans. Single sampling plans based on a 10-percent confidence level are provided in FRSP-10 table IV. Table V gives two points on each of the operating characteristic curves for FRSP-10, as follows:

a. The true failure rates required to maintain qualification 19 times out of 20. b. The true failure rates which would cause disqualification 9 times out of 10.